title: Resistor

text: The resistive element in carbon composition resistors is made from a mixture of finely powdered carbon and an insulating material, usually ceramic. A resin holds the mixture together. The resistance is determined by the ratio of the fill material (the powdered ceramic) to the carbon. Higher concentrations of carbon, which is a good conductor, result in lower resistances. Carbon composition resistors were commonly used in the 1960s and earlier, but are not popular for general use now as other types have better specifications, such as tolerance, voltage dependence, and stress. Carbon composition resistors change value when stressed with over-voltages. Moreover, if internal moisture content, such as from exposure for some length of time to a humid environment, is significant, soldering heat creates a non-reversible change in resistance value. Carbon composition resistors have poor stability with time and were consequently factory sorted to, at best, only 5% tolerance. These resistors are non-inductive, which provides benefits when used in voltage pulse reduction and surge protection applications. Carbon composition resistors have higher capability to withstand overload relative to the component's size.


title: Resistor

text: Carbon composition resistors are still available, but relatively expensive. Values ranged from fractions of an ohm to 22 megohms. Due to their high price, these resistors are no longer used in most applications. However, they are used in power supplies and welding controls. They are also in demand for repair of vintage electronic equipment where authenticity is a factor.


title: Resistor

text: A carbon pile resistor is made of a stack of carbon disks compressed between two metal contact plates. Adjusting the clamping pressure changes the resistance between the plates. These resistors are used when an adjustable load is required, such as in testing automotive batteries or radio transmitters. A carbon pile resistor can also be used as a speed control for small motors in household appliances (sewing machines, hand-held mixers) with ratings up to a few hundred watts. A carbon pile resistor can be incorporated in automatic voltage regulators for generators, where the carbon pile controls the field current to maintain relatively constant voltage. This principle is also applied in the carbon microphone.


title: Resistor

text: In manufacturing carbon film resistors, a carbon film is deposited on an insulating substrate, and a helix is cut in it to create a long, narrow resistive path. Varying shapes, coupled with the resistivity of amorphous carbon (ranging from 500 to 800 μΩ m), can provide a wide range of resistance values. Carbon film resistors feature lower noise compared to carbon composition resistors because of the precise distribution of the pure graphite without binding. Carbon film resistors feature a power rating range of 0.125 W to 5 W at 70 °C. Resistances available range from 1 ohm to 10 megaohm. The carbon film resistor has an operating temperature range of −55 °C to 155 °C. It has 200 to 600 volts maximum working voltage range. Special carbon film resistors are used in applications requiring high pulse stability.


title: Resistor

text: Carbon composition resistors can be printed directly onto printed circuit board (PCB) substrates as part of the PCB manufacturing process. Although this technique is more common on hybrid PCB modules, it can also be used on standard fibreglass PCBs. Tolerances are typically quite large and can be in the order of 30%. A typical application would be non-critical pull-up resistors.


title: Resistor

text: Thick film resistors became popular during the 1970s, and most SMD (surface mount device) resistors today are of this type. The resistive element of thick films is 1000 times thicker than thin films, but the principal difference is how the film is applied to the cylinder (axial resistors) or the surface (SMD resistors).


title: Resistor

text: Thin film resistors are made by sputtering (a method of vacuum deposition) the resistive material onto an insulating substrate. The film is then etched in a similar manner to the old (subtractive) process for making printed circuit boards; that is, the surface is coated with a photo-sensitive material, covered by a pattern film, irradiated with ultraviolet light, and then the exposed photo-sensitive coating is developed, and underlying thin film is etched away.


title: Resistor

text: Because the time during which the sputtering is performed can be controlled, the thickness of the thin film can be accurately controlled. The type of material also varies, consisting of one or more ceramic (cermet) conductors such as tantalum nitride (TaN), ruthenium oxide (), lead oxide (PbO), bismuth ruthenate (), nickel chromium (NiCr), or bismuth iridate ().


title: Resistor

text: The resistance of both thin and thick film resistors after manufacture is not highly accurate; they are usually trimmed to an accurate value by abrasive or laser trimming. Thin film resistors are usually specified with tolerances of 1% and 5%, and with temperature coefficients of 5 to 50 ppm/K. They also have much lower noise levels, on the level of 10–100 times less than thick film resistors. Thick film resistors may use the same conductive ceramics, but they are mixed with sintered (powdered) glass and a carrier liquid so that the composite can be screen-printed. This composite of glass and conductive ceramic (cermet) material is then fused (baked) in an oven at about 850 °C.


title: Resistor

text: When first manufactured, thick film resistors had tolerances of 5%, but standard tolerances have improved to 2% or 1% in the last few decades. Temperature coefficients of thick film resistors are typically ±200 or ±250 ppm/K; a 40-kelvin (70 °F) temperature change can change the resistance by 1%.


title: Resistor

text: Thin film resistors are usually far more expensive than thick film resistors. For example, SMD thin film resistors, with 0.5% tolerances and with 25 ppm/K temperature coefficients, when bought in full size reel quantities, are about twice the cost of 1%, 250 ppm/K thick film resistors.


title: Resistor

text: A common type of axial-leaded resistor today is the metal-film resistor. Metal Electrode Leadless Face (MELF) resistors often use the same technology.


title: Resistor

text: Metal film resistors are usually coated with nickel chromium (NiCr), but might be coated with any of the cermet materials listed above for thin film resistors. Unlike thin film resistors, the material may be applied using different techniques than sputtering (though this is one technique used). The resistance value is determined by cutting a helix through the coating rather than by etching, similar to the way carbon resistors are made. The result is a reasonable tolerance (0.5%, 1%, or 2%) and a temperature coefficient that is generally between 50 and 100 ppm/K. Metal film resistors possess good noise characteristics and low non-linearity due to a low voltage coefficient. They are also beneficial due to long-term stability.


title: Resistor

text: Metal-oxide film resistors are made of metal oxides which results in a higher operating temperature and greater stability and reliability than metal film. They are used in applications with high endurance demands.


title: Resistor

text: Wirewound resistors are commonly made by winding a metal wire, usually nichrome, around a ceramic, plastic, or fiberglass core. The ends of the wire are soldered or welded to two caps or rings, attached to the ends of the core. The assembly is protected with a layer of paint, molded plastic, or an enamel coating baked at high temperature. These resistors are designed to withstand unusually high temperatures of up to 450 °C. Wire leads in low power wirewound resistors are usually between 0.6 and 0.8 mm in diameter and tinned for ease of soldering. For higher power wirewound resistors, either a ceramic outer case or an aluminum outer case on top of an insulating layer is used. If the outer case is ceramic, such resistors are sometimes described as "cement" resistors, though they do not actually contain any traditional cement. The aluminum-cased types are designed to be attached to a heat sink to dissipate the heat; the rated power is dependent on being used with a suitable heat sink, e.g., a 50 W power rated resistor overheats at a fraction of the power dissipation if not used with a heat sink. Large wirewound resistors may be rated for 1,000 watts or more.


title: Resistor

text: Because wirewound resistors are coils they have more undesirable inductance than other types of resistor. However, winding the wire in sections with alternately reversed direction can minimize inductance. Other techniques employ bifilar winding, or a flat thin former (to reduce cross-section area of the coil). For the most demanding circuits, resistors with Ayrton–Perry winding are used.


title: Resistor

text: Applications of wirewound resistors are similar to those of composition resistors with the exception of high frequency applications. The high frequency response of wirewound resistors is substantially worse than that of a composition resistor.


title: Resistor

text: In 1960, Felix Zandman and Sidney J. Stein presented a development of resistor film of very high stability.


title: Resistor

text: The primary resistance element of a foil resistor is a chromium nickel alloy foil several micrometers thick. Chromium nickel alloys are characterized by having a large electrical resistance (about 58 times that of copper), a small temperature coefficient and high resistance to oxidation. Examples are Chromel A and Nichrome V, whose typical composition is 80 Ni and 20 Cr, with a melting point of 1420 °C. When iron is added, the chromium nickel alloy becomes more ductile. The Nichrome and Chromel C are examples of an alloy containing iron. The composition typical of Nichrome is 60 Ni, 12 Cr, 26 Fe, 2 Mn and Chromel C, 64 Ni, 11 Cr, Fe 25. The melting temperature of these alloys are 1350 °C and 1390 °C, respectively.


title: Resistor

text: Since their introduction in the 1960s, foil resistors have had the best precision and stability of any resistor available. One of the important parameters of stability is the temperature coefficient of resistance (TCR). The TCR of foil resistors is extremely low, and has been further improved over the years. One range of ultra-precision foil resistors offers a TCR of 0.14 ppm/°C, tolerance ±0.005%, long-term stability (1 year) 25 ppm, (3 years) 50 ppm (further improved 5-fold by hermetic sealing), stability under load (2000 hours) 0.03%, thermal EMF 0.1 μV/°C, noise −42 dB, voltage coefficient 0.1 ppm/V, inductance 0.08 μH, capacitance 0.5 pF.


title: Resistor

text: The thermal stability of this type of resistor also has to do with the opposing effects of the metal's electrical resistance increasing with temperature, and being reduced by thermal expansion leading to an increase in thickness of the foil, whose other dimensions are constrained by a ceramic substrate.


title: Resistor

text: An ammeter shunt is a special type of current-sensing resistor, having four terminals and a value in milliohms or even micro-ohms. Current-measuring instruments, by themselves, can usually accept only limited currents. To measure high currents, the current passes through the shunt across which the voltage drop is measured and interpreted as current. A typical shunt consists of two solid metal blocks, sometimes brass, mounted on an insulating base. Between the blocks, and soldered or brazed to them, are one or more strips of low temperature coefficient of resistance (TCR) manganin alloy. Large bolts threaded into the blocks make the current connections, while much smaller screws provide volt meter connections. Shunts are rated by full-scale current, and often have a voltage drop of 50 mV at rated current. Such meters are adapted to the shunt full current rating by using an appropriately marked dial face; no change need to be made to the other parts of the meter.


title: Resistor

text: In heavy-duty industrial high-current applications, a grid resistor is a large convection-cooled lattice of stamped metal alloy strips connected in rows between two electrodes. Such industrial grade resistors can be as large as a refrigerator; some designs can handle over 500 amperes of current, with a range of resistances extending lower than 0.04 ohms. They are used in applications such as dynamic braking and load banking for locomotives and trams, neutral grounding for industrial AC distribution, control loads for cranes and heavy equipment, load testing of generators and harmonic filtering for electric substations.


title: Resistor

text: The term "grid resistor" is sometimes used to describe a resistor of any type connected to the control grid of a vacuum tube. This is not a resistor technology; it is an electronic circuit topology.


title: Resistor

text: A resistor may have one or more fixed tapping points so that the resistance can be changed by moving the connecting wires to different terminals. Some wirewound power resistors have a tapping point that can slide along the resistance element, allowing a larger or smaller part of the resistance to be used.


title: Resistor

text: Where continuous adjustment of the resistance value during operation of equipment is required, the sliding resistance tap can be connected to a knob accessible to an operator. Such a device is called a rheostat and has two terminals.


title: Resistor

text: A potentiometer (colloquially, "pot") is a three-terminal resistor with a continuously adjustable tapping point controlled by rotation of a shaft or knob or by a linear slider. The name "potentiometer" comes from its function as an adjustable voltage divider to provide a variable potential at the terminal connected to the tapping point. Volume control in an audio device is a common application of a potentiometer. A typical low power potentiometer "(see drawing)" is constructed of a flat resistance element "(B)" of carbon composition, metal film, or conductive plastic, with a springy phosphor bronze wiper contact "(C)" which moves along the surface. An alternate construction is resistance wire wound on a form, with the wiper sliding axially along the coil. These have lower resolution, since as the wiper moves the resistance changes in steps equal to the resistance of a single turn.


title: Resistor

text: High-resolution multiturn potentiometers are used in precision applications. These have wire-wound resistance elements typically wound on a helical mandrel, with the wiper moving on a helical track as the control is turned, making continuous contact with the wire. Some include a conductive-plastic resistance coating over the wire to improve resolution. These typically offer ten turns of their shafts to cover their full range. They are usually set with dials that include a simple turns counter and a graduated dial, and can typically achieve three-digit resolution. Electronic analog computers used them in quantity for setting coefficients and delayed-sweep oscilloscopes of recent decades included one on their panels.


title: Resistor

text: A resistance decade box or resistor substitution box is a unit containing resistors of many values, with one or more mechanical switches which allow any one of various discrete resistances offered by the box to be dialed in. Usually the resistance is accurate to high precision, ranging from laboratory/calibration grade accuracy of 20 parts per million, to field grade at 1%. Inexpensive boxes with lesser accuracy are also available. All types offer a convenient way of selecting and quickly changing a resistance in laboratory, experimental and development work without needing to attach resistors one by one, or even stock each value. The range of resistance provided, the maximum resolution, and the accuracy characterize the box. For example, one box offers resistances from 0 to 100 megohms, maximum resolution 0.1 ohm, accuracy 0.1%.


title: Resistor

text: There are various devices whose resistance changes with various quantities. The resistance of NTC thermistors exhibit a strong negative temperature coefficient, making them useful for measuring temperatures. Since their resistance can be large until they are allowed to heat up due to the passage of current, they are also commonly used to prevent excessive current surges when equipment is powered on. Similarly, the resistance of a humistor varies with humidity. One sort of photodetector, the photoresistor, has a resistance which varies with illumination.


title: Resistor

text: The strain gauge, invented by Edward E. Simmons and Arthur C. Ruge in 1938, is a type of resistor that changes value with applied strain. A single resistor may be used, or a pair (half bridge), or four resistors connected in a Wheatstone bridge configuration. The strain resistor is bonded with adhesive to an object that is subjected to mechanical strain. With the strain gauge and a filter, amplifier, and analog/digital converter, the strain on an object can be measured.


title: Resistor

text: A related but more recent invention uses a Quantum Tunnelling Composite to sense mechanical stress. It passes a current whose magnitude can vary by a factor of 10 in response to changes in applied pressure.


title: Resistor

text: The value of a resistor can be measured with an ohmmeter, which may be one function of a multimeter. Usually, probes on the ends of test leads connect to the resistor. A simple ohmmeter may apply a voltage from a battery across the unknown resistor (with an internal resistor of a known value in series) producing a current which drives a meter movement. The current, in accordance with Ohm's law, is inversely proportional to the sum of the internal resistance and the resistor being tested, resulting in an analog meter scale which is very non-linear, calibrated from infinity to 0 ohms. A digital multimeter, using active electronics, may instead pass a specified current through the test resistance. The voltage generated across the test resistance in that case is linearly proportional to its resistance, which is measured and displayed. In either case the low-resistance ranges of the meter pass much more current through the test leads than do high-resistance ranges. This allows for the voltages present to be at reasonable levels (generally below 10 volts) but still measurable.


title: Resistor

text: Measuring low-value resistors, such as fractional-ohm resistors, with acceptable accuracy requires four-terminal connections. One pair of terminals applies a known, calibrated current to the resistor, while the other pair senses the voltage drop across the resistor. Some laboratory quality ohmmeters, milliohmmeters, and even some of the better digital multimeters sense using four input terminals for this purpose, which may be used with special test leads called Kelvin clips. Each of the two clips has a pair of jaws insulated from each other. One side of each clip applies the measuring current, while the other connections are only to sense the voltage drop. The resistance is again calculated using Ohm's Law as the measured voltage divided by the applied current.


title: Resistor

text: Resistor characteristics are quantified and reported using various national standards. In the US, MIL-STD-202 contains the relevant test methods to which other standards refer.


title: Resistor

text: The primary standard for resistance, the "mercury ohm" was initially defined in 1884 in as a column of mercury 106.3 cm long and in cross-section, at . Difficulties in precisely measuring the physical constants to replicate this standard result in variations of as much as 30 ppm. From 1900 the mercury ohm was replaced with a precision machined plate of manganin. Since 1990 the international resistance standard has been based on the quantized Hall effect discovered by Klaus von Klitzing, for which he won the Nobel Prize in Physics in 1985.


title: Resistor

text: Resistors of extremely high precision are manufactured for calibration and laboratory use. They may have four terminals, using one pair to carry an operating current and the other pair to measure the voltage drop; this eliminates errors caused by voltage drops across the lead resistances, because no charge flows through voltage sensing leads. It is important in small value resistors (100–0.0001 ohm) where lead resistance is significant or even comparable with respect to resistance standard value.


title: Resistor

text: Axial resistors' cases are usually tan, brown, blue, or green (though other colors are occasionally found as well, such as dark red or dark gray), and display 3–6 colored stripes that indicate resistance (and by extension tolerance), and may include bands to indicate the temperature coefficient and reliability class. In four-striped resistors, the first two stripes represent the first two digits of the resistance in ohms, the third represents a multiplier, and the fourth the tolerance (which if absent, denotes ±20%). For five- and six- striped resistors the third band is the third digit, the fourth is the multiplier and the fifth is the tolerance; a sixth stripe represents the temperature coefficient. The power rating of the resistor is usually not marked and is deduced from its size.


title: Resistor

text: Early 20th century resistors, essentially uninsulated, were dipped in paint to cover their entire body for color-coding. This base color represented the first digit. A second color of paint was applied to one end of the element to represent a second digit, and a color dot (or band) in the middle provided the third digit. The rule was "body, tip, dot", providing two significant digits for value and the decimal multiplier, in that sequence. Default tolerance was ±20%. Closer-tolerance resistors had silver (±10%) or gold-colored (±5%) paint on the other end.


title: Resistor

text: Early resistors were made in more or less arbitrary round numbers; a series might have 100, 125, 150, 200, 300, etc. Early power wirewound resistors, such as brown vitreous-enameled types, were made with a system of preferred values like some of those mentioned here. Resistors as manufactured are subject to a certain percentage tolerance, and it makes sense to manufacture values that correlate with the tolerance, so that the actual value of a resistor overlaps slightly with its neighbors. Wider spacing leaves gaps; narrower spacing increases manufacturing and inventory costs to provide resistors that are more or less interchangeable.


title: Resistor

text: A logical scheme is to produce resistors in a range of values which increase in a geometric progression, so that each value is greater than its predecessor by a fixed multiplier or percentage, chosen to match the tolerance of the range. For example, for a tolerance of ±20% it makes sense to have each resistor about 1.5 times its predecessor, covering a decade in 6 values. More precisely, the factor used is 1.4678 ≈ formula_8, giving values of 1.47, 2.15, 3.16, 4.64, 6.81, 10 for the 1–10-decade (a decade is a range increasing by a factor of 10; 0.1–1 and 10–100 are other examples); these are rounded in practice to 1.5, 2.2, 3.3, 4.7, 6.8, 10; followed by 15, 22, 33, ... and preceded by ... 0.47, 0.68, 1. This scheme has been adopted as the E6 series of the IEC 60063 preferred number values. There are also E12, E24, E48, E96 and E192 series for components of progressively finer resolution, with 12, 24, 48, 96, and 192 different values within each decade. The actual values used are in the IEC 60063 lists of preferred numbers.


title: Resistor

text: A resistor of 100 ohms ±20% would be expected to have a value between 80 and 120 ohms; its E6 neighbors are 68 (54–82) and 150 (120–180) ohms. A sensible spacing, E6 is used for ±20% components; E12 for ±10%; E24 for ±5%; E48 for ±2%, E96 for ±1%; E192 for ±0.5% or better. Resistors are manufactured in values from a few milliohms to about a gigaohm in IEC60063 ranges appropriate for their tolerance. Manufacturers may sort resistors into tolerance-classes based on measurement. Accordingly, a selection of 100 ohms resistors with a tolerance of ±10%, might not lie just around 100 ohm (but no more than 10% off) as one would expect (a bell-curve), but rather be in two groups – either between 5 and 10% too high or 5 to 10% too low (but not closer to 100 ohm than that) because any resistors the factory had measured as being less than 5% off would have been marked and sold as resistors with only ±5% tolerance or better. When designing a circuit, this may become a consideration. This process of sorting parts based on post-production measurement is known as "binning", and can be applied to other components than resistors (such as speed grades for CPUs).


title: Resistor

text: Surface mounted resistors of larger sizes (metric 1608 and above) are printed with numerical values in a code related to that used on axial resistors. Standard-tolerance surface-mount technology (SMT) resistors are marked with a three-digit code, in which the first two digits are the first two significant digits of the value and the third digit is the power of ten (the number of zeroes). For example:


title: Resistor

text: Resistances less than 100 Ω are written: 100, 220, 470. The final zero represents ten to the power zero, which is 1. For example:


title: Resistor

text: Resistances less than 10 Ω have 'R' to indicate the position of the decimal point (radix point). For example:


title: Resistor

text: 000 and 0000 sometimes appear as values on surface-mount zero-ohm links, since these have (approximately) zero resistance.


title: Resistor

text: More recent surface-mount resistors are too small, physically, to permit practical markings to be applied.


title: Resistor

text: Many precision resistors, including surface mount and axial-lead types, are marked with a four-digit code. The first three digits are the significant figures and the fourth is the power of ten. For example:


title: Resistor

text: The former EIA-96 marking system now included in is a more compact marking system intended for physically small high-precision resistors. It uses a two-digit code plus a letter (a total of three alphanumeric characters) to indicate 1% resistance values to three significant digits. The two digits (from "01" to "96") are a code that indicates one of the 96 "positions" in the standard E96 series of 1% resistor values. The uppercase letter is a code that indicates a power of ten multiplier. For example, the marking "01C" represents 10 kOhm; "10C" represents 12.4 kOhm; "96C" represents 97.6 kOhm.


title: Resistor

text: In amplifying faint signals, it is often necessary to minimize electronic noise, particularly in the first stage of amplification. As a dissipative element, even an ideal resistor naturally produces a randomly fluctuating voltage, or noise, across its terminals. This Johnson–Nyquist noise is a fundamental noise source which depends only upon the temperature and resistance of the resistor, and is predicted by the fluctuation–dissipation theorem. Using a larger value of resistance produces a larger voltage noise, whereas a smaller value of resistance generates more current noise, at a given temperature.


title: Resistor

text: The thermal noise of a practical resistor may also be larger than the theoretical prediction and that increase is typically frequency-dependent. Excess noise of a practical resistor is observed only when current flows through it. This is specified in unit of μV/V/decade – μV of noise per volt applied across the resistor per decade of frequency. The μV/V/decade value is frequently given in dB so that a resistor with a noise index of 0 dB exhibits 1 μV (rms) of excess noise for each volt across the resistor in each frequency decade. Excess noise is thus an example of 1/"f" noise. Thick-film and carbon composition resistors generate more excess noise than other types at low frequencies. Wire-wound and thin-film resistors are often used for their better noise characteristics. Carbon composition resistors can exhibit a noise index of 0 dB while bulk metal foil resistors may have a noise index of −40 dB, usually making the excess noise of metal foil resistors insignificant. Thin film surface mount resistors typically have lower noise and better thermal stability than thick film surface mount resistors. Excess noise is also size-dependent: in general, excess noise is reduced as the physical size of a resistor is increased (or multiple resistors are used in parallel), as the independently fluctuating resistances of smaller components tend to average out.


title: Resistor

text: While not an example of "noise" per se, a resistor may act as a thermocouple, producing a small DC voltage differential across it due to the thermoelectric effect if its ends are at different temperatures. This induced DC voltage can degrade the precision of instrumentation amplifiers in particular. Such voltages appear in the junctions of the resistor leads with the circuit board and with the resistor body. Common metal film resistors show such an effect at a magnitude of about 20 μV/°C. Some carbon composition resistors can exhibit thermoelectric offsets as high as 400 μV/°C, whereas specially constructed resistors can reduce this number to 0.05 μV/°C. In applications where the thermoelectric effect may become important, care has to be taken to mount the resistors horizontally to avoid temperature gradients and to mind the air flow over the board.


title: Resistor

text: The failure rate of resistors in a properly designed circuit is low compared to other electronic components such as semiconductors and electrolytic capacitors. Damage to resistors most often occurs due to overheating when the average power delivered to it greatly exceeds its ability to dissipate heat (specified by the resistor's "power rating"). This may be due to a fault external to the circuit but is frequently caused by the failure of another component (such as a transistor that shorts out) in the circuit connected to the resistor. Operating a resistor too close to its power rating can limit the resistor's lifespan or cause a significant change in its resistance. A safe design generally uses overrated resistors in power applications to avoid this danger.


title: Resistor

text: Low-power thin-film resistors can be damaged by long-term high-voltage stress, even below maximum specified voltage and below maximum power rating. This is often the case for the startup resistors feeding a switched-mode power supply integrated circuit.


title: Resistor

text: Carbon film and composition resistors can fail (open circuit) if running close to their maximum dissipation. This is also possible but less likely with metal film and wirewound resistors.


title: Resistor

text: There can also be failure of resistors due to mechanical stress and adverse environmental factors including humidity. If not enclosed, wirewound resistors can corrode.


title: Resistor

text: Surface mount resistors have been known to fail due to the ingress of sulfur into the internal makeup of the resistor. This sulfur chemically reacts with the silver layer to produce non-conductive silver sulfide. The resistor's impedance goes to infinity. Sulfur resistant and anti-corrosive resistors are sold into automotive, industrial, and military applications. ASTM B809 is an industry standard that tests a part's susceptibility to sulfur.


title: Resistor

text: An alternative failure mode can be encountered where large value resistors are used (hundreds of kilohms and higher). Resistors are not only specified with a maximum power dissipation, but also for a maximum voltage drop. Exceeding this voltage causes the resistor to degrade slowly reducing in resistance. The voltage dropped across large value resistors can be exceeded before the power dissipation reaches its limiting value. Since the maximum voltage specified for commonly encountered resistors is a few hundred volts, this is a problem only in applications where these voltages are encountered.


title: Resistor

text: Variable resistors can also degrade in a different manner, typically involving poor contact between the wiper and the body of the resistance. This may be due to dirt or corrosion and is typically perceived as "crackling" as the contact resistance fluctuates; this is especially noticed as the device is adjusted. This is similar to crackling caused by poor contact in switches, and like switches, potentiometers are to some extent self-cleaning: running the wiper across the resistance may improve the contact. Potentiometers which are seldom adjusted, especially in dirty or harsh environments, are most likely to develop this problem. When self-cleaning of the contact is insufficient, improvement can usually be obtained through the use of contact cleaner (also known as "tuner cleaner") spray. The crackling noise associated with turning the shaft of a dirty potentiometer in an audio circuit (such as the volume control) is greatly accentuated when an undesired DC voltage is present, often indicating the failure of a DC blocking capacitor in the circuit.


title: Panthéon

text: The Panthéon (, from the Classical Greek word , , '[temple] to all the gods') is a monument in the 5th arrondissement of Paris, France. It stands in the Latin Quarter, atop the , in the centre of the , which was named after it. The edifice was built between 1758 and 1790, from designs by , at the behest of King Louis XV of France; the king intended it as a church dedicated to Saint Genevieve, Paris's patron saint, whose relics were to be housed in the church. Neither Soufflot nor Louis XV lived to see the church completed.


title: Panthéon

text: By the time the construction was finished, the French Revolution had started; the National Constituent Assembly voted in 1791 to transform the Church of Saint Genevieve into a mausoleum for the remains of distinguished French citizens, modelled on the Pantheon in Rome which had been used in this way since the 16th century. The first was , although his remains were removed from the building a few years later. The Panthéon was twice restored to church usage in the course of the 19th century—although Soufflot's remains were transferred inside it in 1829—until the French Third Republic finally decreed the building's exclusive use as a mausoleum in 1881. The placement of Victor Hugo's remains in the crypt in 1885 was its first entombment in over 50 years.


title: Panthéon

text: The successive changes in the Panthéon's purpose resulted in modifications of the pedimental sculptures and the capping of the dome by a cross or a flag; some of the originally existing windows were blocked up with masonry in order to give the interior a darker and more funereal atmosphere, which compromised somewhat Soufflot's initial attempt at combining the lightness and brightness of the Gothic cathedral with classical principles. The architecture of the Panthéon is an early example of Neoclassicism, surmounted by a dome that owes some of its character to Bramante's .


title: Panthéon

text: In 1851, Léon Foucault conducted a demonstration of diurnal motion at the Panthéon by suspending a pendulum from the ceiling, a copy of which is still visible today. As of December 2021 the remains of 81 people (75 men and six women) had been transferred to the Panthéon. More than half of all the were made under Napoleon's rule during the First Empire.


title: Panthéon

text: The site of the Panthéon had great significance in Paris history, and was occupied by a series of monuments. It was on Mount Lucotitius, a height on the Left Bank where the forum of the Roman town of Lutetia was located. It was also the original burial site of Saint Genevieve, who had led the resistance to the Huns when they threatened Paris in 451. In 508, Clovis, King of the Franks, constructed a church there, where he and his wife were later buried in 511 and 545. The church, originally dedicated to Saints Peter and Paul, was rededicated to Saint Genevieve, who became the patron saint of Paris. It was at the centre of the Abbey of Saint Genevieve, a centre of religious scholarship in the Middle Ages. Her relics were kept in the church, and were brought out for solemn processions when dangers threatened the city.


title: Panthéon

text: King Louis XV vowed in 1744 that if he recovered from his illness he would replace the dilapidated church of the Abbey of St Genevieve with a grander building worthy of the patron saint of Paris. He did recover, but ten years passed before the reconstruction and enlargement of the church was begun. In 1755 The Director of the King's public works, Abel-François Poisson, marquis de Marigny, chose Jacques-Germain Soufflot to design the church. Soufflot (1713–1780) had studied classical architecture in Rome over 1731–38. Most of his early work was done in Lyon. Saint Genevieve became his life's work; it was not finished until after his death.


title: Panthéon

text: His first design was completed in 1755, and was clearly influenced by the work of Bramante he had studied in Italy. It took form of a Greek cross, with four naves of equal length, and monumental dome over the crossing in the centre, and a classical portico with Corinthian columns and a peristyle with a triangular pediment on the main facade. The design was modified five times over the following years, with the addition of a narthex, a choir, and two towers. The design was not finalised until 1777.


title: Panthéon

text: The foundations were laid in 1758, but due to economic problems work proceeded slowly. In 1780, Soufflot died and was replaced by his student Jean-Baptiste Rondelet. The re-modelled Abbey of St. Genevieve was finally completed in 1790, shortly after the beginning of the French Revolution.


title: Panthéon

text: The building is 110 metres long by 84 metres wide, and 83 metres high, with the crypt beneath of the same size. The ceiling was supported by isolated columns, which supported an array of barrel vaults and transverse arches. The massive dome was supported by pendentives rested upon four massive pillars. Critics of the plan contended that the pillars could not support such a large dome. Soufflot strengthened the stone structure with a system of iron rods, a predecessor of modern reinforced buildings. The bars had deteriorated by the 21st century, and a major restoration project to replace them is being carried out between 2010 and 2020.


title: Panthéon

text: The dome is actually three domes, fitting within each other. The first, lowest dome, has a coffered ceiling with rosettes, and is open in the centre. Looking through this dome, the second dome is visible, decorated with the fresco "The Apotheosis of Saint Genevieve" by Antoine Gros. The outermost dome, visible from the outside, is built of stone bound together with iron cramps and covered with lead sheathing, rather than of carpentry construction, as was the common French practice of the period. Concealed buttresses inside the walls give additional support to the dome.


title: Panthéon

text: The Church of Saint Genevieve was nearly complete, with only the interior decoration unfinished, when the French Revolution began in 1789. In 1790, the Marquis de Vilette proposed that it be made a temple devoted to liberty, on the model of the Pantheon in Rome. "Let us install statues of our great men and lay their ashes to rest in its underground recesses." The idea was formally adopted in April, 1791, after the death of the prominent revolutionary figure, The Comte de Mirabeau, the President of the National Constituent Assembly on April 2, 1791. On April 4, 1791, the Assembly decreed "that this religious church become a temple of the nation, that the tomb of a great man become the altar of liberty." They also approved a new text over the entrance: "A grateful nation honors its great men." On the same day the declaration was approved, the funeral of Mirabeau was held in the church.


title: Panthéon

text: The ashes of Voltaire were placed in the Panthéon in a lavish ceremony on 11 July 1791, followed by the remains of several revolutionaries, including Jean-Paul Marat, replacing Mirabeau and of the philosopher Jean-Jacques Rousseau. In the rapid shifts of power of the Revolutionary period, two of the first men honored in Pantheon, Mirabeau and Marat, were declared enemies of the Revolution, and their remains were removed. Finally, the new government of the French Convention decreed in February, 1795 that no one should be placed in the Pantheon who had not been dead at least ten years.


title: Panthéon

text: Soon after the church was transformed into a mausoleum, the Assembly approved architectural changes to make the interior darker and more solemn. The architect Quatremère de Quincy bricked up the lower windows and frosted the glass of the upper windows to reduce the light, and removed most of the ornament from the exterior. The architectural lanterns and bells were removed the facade. All of the religious friezes and statues were destroyed in 1791; it was replaced by statuary and murals on patriotic themes.


title: Panthéon

text: Napoleon Bonaparte, when he became First Consul in 1801, signed a Concordat with the Pope, agreeing to restore former church properties, including the Panthéon. The Panthéon was under the jurisdiction of the canons of the Cathedral of Notre Dame de Paris. Celebrations of important events, such as the victory of Napoleon at the Battle of Austerlitz, were held there. However, the crypt of the church kept its official function as the resting place for illustrious Frenchmen. A new entrance directly to the crypt was created via the eastern porch (1809–1811). The artist Antoine-Jean Gros was commissioned to decorate the interior of the cupola. It combined the secular and religious aspects of the church; it showed the Genevieve being conducted to heaven by angels, in the presence of great leaders of France, from Clovis I and Charlemagne to Napoleon and the Empress Josephine.


title: Panthéon

text: During the reign of Napoleon, the remains of forty-one illustrious Frenchmen were placed in the crypt. They were mostly military officers, senators and other high officials of the Empire, but also included the explorer Louis-Antoine de Bougainville and the painter Joseph-Marie Vien, the teacher of Napoleon's official painter, Jacques-Louis David.


title: Panthéon

text: During the Bourbon Restoration which followed the fall of Napoleon, in 1816 Louis XVIII of France restored the entire Panthéon, including the crypt, to the Catholic Church. The church was also at last officially consecrated in the presence of the King, a ceremony which had been omitted during the Revolution. The sculpture on the pediment by Jean Guillaume Moitte, called "The Fatherland crowning the heroic and civic virtues" was replaced by a religious-themed work by David d'Angers. The reliquary of Saint Genevieve had been destroyed during the Revolution, but a few relics were found and restored to the church (They are now in the neighboring Church of Saint-Etienne-du-Mont). In 1822 François Gérard was commissioned to decorate the pendentives of the dome with new works representing Justice, Death, the Nation, and Fame. Jean-Antoine Gros was commissioned to redo his fresco on the inner dome, replacing Napoleon with Louis XVIII, as well as figures of Louis XVI and Marie Antoinette. The new version of the cupola was inaugurated in 1824 by Charles X. As to the crypt where the tombs were located, it was locked and closed to visitors.


title: Panthéon

text: The French Revolution of 1830 placed Louis Philippe I on the throne. He expressed sympathy for Revolutionary values, and on 26 August 1830, the church once again became the Pantheon. However, the crypt remained closed to the public, and no new remains were added. The only change made was to the main pediment, which had been remade with a radiant cross; it was remade again by D'Angers with a patriotic work called "The Nation Distributing Crowns Handed to Her by Liberty, to Great Men, Civil and Military, While History Inscribes Their Names."


title: Panthéon

text: Louis Philippe was overthrown in 1848 and replaced by the elected government of the Second French Republic, which valued revolutionary themes. The new government designated the Pantheon "The Temple of Humanity", and proposed to decorate it with sixty new murals honouring human progress in all fields. In 1851 the Foucault Pendulum of astronomer Léon Foucault was hung beneath the dome to illustrate the rotation of the earth. However, on complaints from the Church, it was removed in December of the same year.


title: Panthéon

text: Louis Napoléon, nephew of the Emperor, was elected President of France in December 1848, and in 1852 staged a coup-d'état and made himself Emperor. Once again the Pantheon was returned to the church, with the title of "National Basilica". The remaining relics of Saint Genevieve were restored to the church, and two groups of sculpture commemorating events in the life of the Saint were added. The crypt remained closed.


title: Panthéon

text: The Basilica suffered damage from German shelling during the 1870 Franco-Prussian War. During the brief reign of the Paris Commune in May 1871, it suffered more damage during fighting between the Commune soldiers and the French Army. During the early years of the Third Republic, under conservative governments, it functioned as a church, but the interior walls were largely bare. Beginning in 1874, The interior was redecorated with new murals and sculptural groups linking French history and the history of the church, by notable artists including Puvis de Chavannes and Alexandre Cabanel, and the artist Antoine-Auguste-Ernest Hébert, who made a mosaic under the vault of the apsidal chapel called "Christ Showing the Angel of France the Destiny of Her People".


title: Panthéon

text: In 1881, a decree was passed to transform the Church of Saint Genevieve into a mausoleum again. Victor Hugo was the first to be placed in the crypt afterwards. The subsequent governments approved the entry of literary figures, including the writer Émile Zola (1908), and, after World War I, leaders of the French socialist movement, including Léon Gambetta (1920) and Jean Jaurès (1924). The Third Republic governments also decreed that the building should be decorated with sculpture representing "the golden ages and great men of France." The principal works remaining from this period include the sculptural group called "The National Assembly", commemorating the French Revolution; a statue of Mirabeau, the first man interred in the Pantheon, by Jean-Antoine Ingabert; (1889–1920); and two patriotic murals in the apse "Victory Leading the Armies of the Republic" to "Towards Glory" by Édouard Detaille, and "Glory Entering the Temple, Followed by Poets, Philosophers, Scientists and Warriors" , by Marie-Désiré-Hector d'Espouy (1906).


title: Panthéon

text: The short-lived Fourth Republic (1948–1958) following World War II pantheonized two physicists, Paul Langevin and Jean Perrin; a leader of the abolitionist movement, Victor Schœlcher; early leader of Free France and colonial administrator Félix Éboué; and Louis Braille, inventor of the Braille writing system, in 1952.


title: Panthéon

text: Under the Fifth Republic of President Charles de Gaulle, the first person to be buried in the Panthéon was the Resistance leader Jean Moulin. Modern figures buried in recent years include Nobel Peace Prize winner René Cassin (1987) known for drafting the Universal Declaration of Human Rights; Jean Monnet who was a moving force in the creation of the ECSC, the forerunner of the EU, was interred in the 100th anniversary of his birth; Nobel laureates physicists and chemists Marie Curie and Pierre Curie (1995); the writer and culture minister André Malraux (1996); and the lawyer, politician Simone Veil (2018). In 2021, Josephine Baker was inducted into the Pantheon, becoming the first Black woman to receive that honor.


title: Panthéon

text: The final plan of the dome was accepted in 1777, and it was completed in 1790. It was designed to rival those of St. Peter's Basilica in Rome and St Paul's Cathedral in London. Unlike the dome of Les Invalides in Paris, which has a wooden framework, the dome is constructed entirely of stone. It is actually three domes, one within the other, with the painted ceiling, visible from below, on the second dome. The dome is 83.0 metres (272 ft) high, compared with the tallest dome in the world, St. Peter's Basilica at 136.57 metres (448.1 ft).


title: Panthéon

text: The dome is capped by a cross. However, a statue of Saint Genevieve was initially supposed to sit at the top of the dome. A cross was put temporarily in 1790. After the transformation into a mausoleum in 1791, it was planned that the cross would be replaced by a statue representing Fame. The project was however abandoned. Between 1830 and 1851, a flag was put instead. The cross returned after Louis-Napoleon Bonaparte restored the building to church use. The cross was replaced with a red flag during the Paris Commune in 1871. A cross returned subsequently.


title: Panthéon

text: Looking up from the crossing of the transept beneath the dome, the painting by Jean-Antoine Gros, the "Apotheosis of Saint Genevieve" (1811–1834), is visible through the opening in the lowest cupola. The triangle in the center symbolizes the Trinity, surrounded by a halo of light. The Hebrew characters spell the name of God. The only character seen in full is Saint Genevieve herself, seated on a rocky promontory. The groups around the painting, made during the Restoration of the Monarchy, represent Kings of France who played an important role in protecting the church. To the left of Saint Genevieve is a group including Clovis, the first King to convert to Christianity. The second group is centred around Charlemagne, who created the first universities. The third group is centred around Louis IX of France, or Saint Louis, with the Crown of Thorns which he brought back from the Holy Land to place in the church of Sainte-Chapelle. The last group is centred around Louis XVIII, the last King of the Restoration, and his niece, looking up into the clouds at the martyred Louis XVI and Marie-Antoinette. The angels in the scene are carrying the "Chartre", the document by which Louis XVIII re-established the church after the French Revolution.


title: Panthéon

text: The four pendentives, or arches, which support the dome are decorated with paintings from the same period by François Gérard depicting "Glory", "Death", "The Nation" and "Justice" (1821–37).


title: Panthéon

text: The facade and peristyle on the east side, modeled after a Greek temple, features Corinthian columns and pedimental sculpture by David d'Angers, completed in 1837. The sculpture on this pediment, replacing an early pediment with religious themes, represents "The Nation distributing crowns handed to her by Liberty to great men, civil and military, while history inscribes their names". To the left are figures of distinguished scientists, philosophers, and statesmen, including Rousseau, Voltaire, Lafayette, and Bichat. To the right is Napoleon Bonaparte, along with soldiers from each military service and students in uniform from the École Polytechnique. Below is the inscription: "To the great men, from a grateful nation" ("Aux grands hommes la patrie reconnaissante"). This was added in 1791, when the Panthéon was created. It was removed during the Restoration of the monarchy, then put back in 1830.


title: Panthéon

text: Below the peristyle are five sculpted bas-reliefs; the two reliefs over the main doors, commissioned during the Revolution, represent the two main purposes of the building: "Public Education" (left) and "Patriotic Devotion" (right).


title: Panthéon

text: The facade originally had large windows, but they were replaced when the church became a mausoleum, to make the interior darker and more somber.


title: Panthéon

text: The primary decoration of the Western Nave is a series of paintings, beginning in the Narthex, depicting the lives of Saint Denis, the patron saint of Paris, and longer series on the life of Saint Genevieve, by Puvis de Chavannes, Alexandre Cabanel, Jules Eugène Lenepveu and other notable history painters of the 19th century. The paintings of the Southern nave and Northern Nave continue this series on the Christian heroes of France, including scenes from the lives of Charlemagne, Clovis, Louis IX of France and Joan of Arc. From 1906 to 1922 the Panthéon was the site of Auguste Rodin's famous sculpture "The Thinker".


title: Panthéon

text: In 1851, physicist Léon Foucault demonstrated the rotation of the Earth by constructing a pendulum beneath the central dome. The original sphere from the pendulum was temporarily displayed at the Panthéon in the 1990s (starting in 1995) during renovations at the Musée des Arts et Métiers. The original pendulum was later returned to the Musée des Arts et Métiers, and a copy is now displayed at the Panthéon. It has been listed since 1920 as a "monument historique" by the French Ministry of Culture.


title: Panthéon

text: Interment in the crypt of the Panthéon is severely restricted and is allowed only by a parliamentary act for "National Heroes". Similar high honours exist in Les Invalides for historical military leaders such as Napoléon, Turenne and Vauban.


title: Panthéon

text: Among those buried in its necropolis are Voltaire, Rousseau, Victor Hugo, Émile Zola, Jean Moulin, Louis Braille, Jean Jaurès and Soufflot, its architect. In 1907 Marcellin Berthelot was buried with his wife Mme Sophie Berthelot. Marie Curie was interred in 1995, the first woman interred on merit. Geneviève de Gaulle-Anthonioz and Germaine Tillion, heroines of the French resistance, were interred in 2015. Simone Veil was interred in 2018, and her husband Antoine Veil was interred alongside her so that they would not be separated.


title: Panthéon

text: The widely repeated story that the remains of Voltaire were stolen by religious fanatics in 1814 and thrown into a garbage heap is false. Such rumours resulted in the coffin being opened in 1897, which confirmed that his remains were still present.


title: Panthéon

text: On 30 November 2002, in an elaborate but solemn procession, six Republican Guards carried the coffin of Alexandre Dumas (1802–1870), the author of "The Three Musketeers" and other famous novels, to the Panthéon. Draped in a blue-velvet cloth inscribed with the Musketeers' motto ""Un pour tous, tous pour un"" ("One for all, all for one"), the remains had been transported from their original interment site in the Cimetière de Villers-Cotterêts in Aisne, France. In his speech, President Jacques Chirac stated that an injustice was being corrected with the proper honouring of one of France's greatest authors.


title: Panthéon

text: In January 2007, President Jacques Chirac unveiled a plaque in the Panthéon to more than 2,600 people recognised as Righteous Among the Nations by the Yad Vashem memorial in Israel for saving the lives of Jews who would otherwise have been deported to concentration camps. The tribute in the Panthéon underlines the fact that around three-quarters of the country's Jewish population survived the war, often thanks to ordinary people who provided help at the risk of their own life.


title: Qualcomm Snapdragon

text: Snapdragon is a suite of system on a chip (SoC) semiconductor products for mobile devices designed and marketed by Qualcomm Technologies Inc. The Snapdragon's central processing unit (CPU) uses the ARM architecture. A single SoC may include multiple CPU cores, an Adreno graphics processing unit (GPU), a Snapdragon wireless modem, a Hexagon digital signal processor (DSP), a Qualcomm Spectra image signal processor (ISP) and other software and hardware to support a smartphone's global positioning system (GPS), camera, video, audio, gesture recognition and AI acceleration. As such, Qualcomm often refers to the Snapdragon as a "mobile platform" (e.g. Snapdragon 865 5G Mobile Platform). Snapdragon semiconductors are embedded in devices of various systems, including Android, Windows Phone and netbooks. They are also used in cars, wearable devices and other devices. In addition to the processors, the Snapdragon line includes modems, Wi-Fi chips and mobile charging products.


title: Qualcomm Snapdragon

text: The Snapdragon QSD8250 was released in December 2007. It included the first 1 GHz processor for mobile phones. Qualcomm introduced its "Krait" microarchitecture in the second generation of Snapdragon SoCs in 2011, allowing each processor core to adjust its speed based on the device's needs. At the 2013 Consumer Electronics Show, Qualcomm introduced the first of the Snapdragon 800 series and renamed prior models as the 200, 400 and 600 series. Several new iterations have been introduced since, such as the Snapdragon 805, 810, 615 and 410. Qualcomm re-branded its modem products under the Snapdragon name in February 2015. Asus, HP and Lenovo have begun selling laptops with Snapdragon-based CPUs running Windows 10 under the name "Always Connected PCs", marking an entry into the PC market for Qualcomm and the ARM architecture.


title: Qualcomm Snapdragon

text: Qualcomm announced it was developing the Scorpion central processing unit (CPU) in November 2007. The Snapdragon system on chip (SoC) was announced in November 2006 and included the Scorpion processor, as well as other semiconductors. This also included Qualcomm's first custom Hexagon digital signal processor (DSP).


title: Qualcomm Snapdragon

text: According to a Qualcomm spokesperson, it was named Snapdragon, because "Snap and Dragon sounded fast and fierce." The following month, Qualcomm acquired Airgo Networks for an undisclosed amount; it said Airgo's 802.11a/b/g and 802.11n Wi-Fi technology would be integrated with the Snapdragon product suite. Early versions of Scorpion had a processor core design similar to the Cortex-A8.


title: Qualcomm Snapdragon

text: The first Snapdragon shipments were of the QSD8250 in November 2007. According to CNET, Snapdragon claim to fame was having the first 1 GHz mobile made processor. Most smartphones at the time were using 500 MHz processors. The first generation of Snapdragon products supported a 720p resolution, 3D graphics and a 12-megapixel camera. By November 2008, 15 device manufacturers decided to embed Snapdragon chips in their consumer electronics products.


title: Qualcomm Snapdragon

text: In November 2008, Qualcomm announced it would also compete against Intel in the netbook processor market with dual-core Snapdragon system-on-chips planned for late 2009. It demonstrated a Snapdragon processor that consumed less power than Intel chips announced around the same time and claimed it would also cost less when released. That same month, Qualcomm introduced a Snapdragon-based prototype netbook called Kayak that used 1.5 GHz processors and was intended for developing markets.


title: Qualcomm Snapdragon

text: In May 2009, Java SE was ported and optimized for Snapdragon. At the November 2009 Computex Taipei show, Qualcomm announced the QSD8650A addition to the Snapdragon product suite, which was based on 45 nanometer manufacturing processes. It featured a 1.2 GHz processor and had lower power consumption than prior models.


title: Qualcomm Snapdragon

text: By late 2009, smartphone manufacturers announced they would be using Snapdragon SoCs in the Acer Liquid Metal, HTC HD2, Toshiba TG01 and the Sony Ericsson Xperia X10. Lenovo announced the first netbook product using Snapdragon SoCs that December. According to "PC World", mobile devices using Snapdragon had longer battery life and were smaller in size than those using other SoCs.


title: Qualcomm Snapdragon

text: By June 2010, Snapdragon chips were embedded in 20 available consumer devices and incorporated into 120 product designs in development. Apple had a dominant market position for smartphones at the time and did not incorporate Snapdragon into any of its products. The success of Snapdragon therefore relied on competing Android phones, such as Google's Nexus One and the HTC Incredible, challenging Apple's market position. Android devices did end up taking market share from the iPhone and predominantly used Snapdragon.


title: Qualcomm Snapdragon

text: There was an "unconfirmed but widely circulated report" speculating that Apple was going to start using Snapdragon SoCs in Verizon-based iPhones. As of 2012, Apple was still using their own Ax semiconductor designs. Support for the Windows Phone 7 operating systems was added to Snapdragon in October 2010.


title: Qualcomm Snapdragon

text: By 2011 Snapdragon was embedded in Hewlett Packard's WebOS devices and had a 50% market share of a $7.9 billion smartphone processor market.


title: Qualcomm Snapdragon

text: As of July 2014, the market share of Android phones had grown to 84.6 percent, and Qualcomm's Snapdragon chips were embedded in 41% of smartphones.


title: Qualcomm Snapdragon

text: Snapdragon chips are also used in most Android-based smartwatches. Snapdragon products have also been used in virtual reality products, in vehicles like the Maserati Quattroporte and Cadillac XTS and in other applications.


title: Qualcomm Snapdragon

text: In June 2010, Qualcomm began sampling the third generation of Snapdragon products; two dual-core 1.2 GHz system on chips (SoC) called the Mobile Station Modem (MSM) 8260 and 8660. The 8260 was for GSM, UMTS and HSPA+ networks, while the 8660 was for CDMA2000 and EVDO networks. That November Qualcomm announced the MSM8960 for LTE networks.


title: Qualcomm Snapdragon

text: In early 2011, Qualcomm announced a new processor architecture called Krait, which used the ARM v7 instruction set, but was based on Qualcomm's own processor design. The processors were called S4 and had a feature named Asynchronous Symmetrical Multi-Processing (aSMP), meaning each processor core adjusted its clock speed and voltage based on the device's activity in order to optimize battery usage. Prior models were renamed to S1, S2 and S3 to distinguish each generation.


title: Qualcomm Snapdragon

text: The S4-based generation of Snapdragon SoCs began shipping to product manufacturers with the MSM8960 in February 2012. In benchmark tests by Anandtech, the MSM8960 had better performance than any other processor tested. In an overall system benchmark, the 8960 obtained a score of 907, compared to 528 and 658 for the Galaxy Nexus and HTC Rezound respectively. In a Quadrant benchmark test, which assesses raw processing power, a dual-core Krait processor had a score of 4,952, whereas the quad-core Tegra 3 was just under 4,000. The quad-core version, APQ8064, was made available in July 2012. It was the first Snapdragon SoC to use Qualcomm's Adreno 320 graphics processing unit (GPU).


title: Qualcomm Snapdragon

text: Adoption of Snapdragon contributed to Qualcomm's transition from a wireless modem company to one that also produces a wider range of hardware and software for mobile devices. In July 2011 Qualcomm acquired certain assets from GestureTek in order to incorporate its gesture recognition intellectual property into Snapdragon SoCs. In mid-2012 Qualcomm announced the Snapdragon software development kit (SDK) for Android devices at the Uplinq developer conference. The SDK includes tools for facial recognition, gesture recognition, noise cancellation and audio recording. That November Qualcomm acquired some assets from EPOS Development in order to integrate its stylus and gesture recognition technology into Snapdragon products. It also collaborated with Microsoft to optimize Windows Phone 8 for Snapdragon semiconductors.


title: Qualcomm Snapdragon

text: By 2012, the Snapdragon S4 (Krait core) had taken a dominant share from other Android system-on-chips like Nvidia Tegra and Texas Instruments OMAP which caused the latter to exit the market. As of July 2014, the market share of Android phones had grown to 84.6 percent, and Qualcomm's Snapdragon chips powered 41% of smartphones.


title: Qualcomm Snapdragon

text: However, the September 2013 debut of Apple's 64-bit A7 chip in the iPhone 5S forced Qualcomm to rush out a competing 64-bit solution, despite the capable performance of the Snapdragon 800/801/805, since their existing Krait cores were only 32-bit. The first 64-bit SoCs, the Snapdragon 808 and 810, were rushed to market using generic Cortex-A57 and Cortex-A53 cores and suffered from overheating problems and throttling, particularly the 810, which led to Samsung ditching Snapdragon for its Galaxy S6 flagship phone.


title: Qualcomm Snapdragon

text: The entry-level 200 series was expanded with six new processors using 28 nanometer manufacturing and dual or quad-core options in June 2013. The entry-level Snapdragon 210, intended for low-cost phones, was announced in September 2014.


title: Qualcomm Snapdragon

text: After Qualcomm's first attempt at 64-bit system on a chip, they created a new in-house architecture that in later models showed better thermal performance, especially when compared to the Snapdragon models launched after 2015, like the Snapdragon 820.


title: Qualcomm Snapdragon

text: In early 2016, Qualcomm launched the Snapdragon 820, an ARM 64-bit quad-core processor using in-house designed Kryo cores. Qualcomm launched an updated Snapdragon 821 later in the year with higher clock speeds and slightly better performance. The Snapdragon 820 family uses Samsung's 14-nanometer FinFET process. Qualcomm also released the Qualcomm Snapdragon Neural Processing Engine SDK which was the first AI acceleration on smartphones.


title: Qualcomm Snapdragon

text: Qualcomm announced the octa-core Snapdragon 835 SoC on 17 November 2016. Released the following year, it uses Kryo 280 cores and is built using Samsung's 10 nanometer FinFET process. At initial launch, due to Samsung's role in manufacturing the chip, its mobile division also acquired the initial inventory of the chip. That means that no other phone maker was able to manufacture products containing the Snapdragon 835 until Samsung released its flagship device of the year, the Galaxy S8.


title: Qualcomm Snapdragon

text: At Computex 2017 in May, Qualcomm and Microsoft announced plans to launch Snapdragon-based laptops running Windows 10. Qualcomm partnered with HP, Lenovo, and Asus to release slim portables and 2-in-1 devices powered by the Snapdragon 835.


title: Qualcomm Snapdragon

text: In December 2017, Qualcomm announced the octa-core Snapdragon 845. It uses the same 10-nanometer manufacturing process as the earlier Snapdragon 835 but introduced a new processor architecture, Kryo 385, designed for better battery life, photography, and for use with artificial intelligence apps.


title: Qualcomm Snapdragon

text: In early 2018, Qualcomm introduced the 7 series, which sits between the 6 and 8 series in terms of pricing and performance. The 700 launched with octa-core models Snapdragon 710 and 712, using the Kryo 360 processor architecture, and built on a 10-nanometer manufacturing process.


title: Qualcomm Snapdragon

text: In 2019, Qualcomm released new variants of its mobile processors, with the Snapdragon 855 replacing the 845. The Snapdragon 855 competes against other high end system-on-chip solutions like the Apple A12, and Kirin 980. The Snapdragon 855 features Kryo 485 cores, built on TSMC's 7 nanometer process. The Snapdragon 730 and 730G replaced the 710 and 712. The newer 730 and 730G feature Kryo 460 cores, built on Samsung's 8-nanometer process.


title: Qualcomm Snapdragon

text: In December 2019, Qualcomm announced the Snapdragon 865 and Snapdragon 765, which succeeded the Snapdragon 855/855+ and Snapdragon 730/730G respectively. The Snapdragon 765 has integrated 5G, while the Snapdragon 865 is assisted by a separate Qualcomm X55 5G modem. Despite lacking integrated 5G, the Snapdragon 865 is incompatible with 4G phones.


title: Qualcomm Snapdragon

text: In May 2020, Qualcomm announced the new Snapdragon 768G 5G processor, an upgraded version of the 765G processor. The main difference between the 765G and 768G is that the 768G will offer 15 percent increase in performance and higher clock speed on the CPU, up to 2.8 GHz from 2.4 GHz.


title: Qualcomm Snapdragon

text: In September 2020, Qualcomm unveiled the Snapdragon 750G processor, the latest addition to the 7-series, designed to bring 5G support for low-latency mobile gaming.


title: Qualcomm Snapdragon

text: In December 2020, Qualcomm unveiled the Snapdragon 888. The major differences compared to the 865/+ is a new core, designed by ARM, the ARM Cortex X1, support for LPDDR5-6400 and a built in 5G modem, meaning the X55 Modem is not required. The 888 is based on Samsung 5 nm, with a TDP of 5 watts, but this can be altered by the manufacturer.


title: Qualcomm Snapdragon

text: In May 2022, Qualcomm announced their new model Snapdragon 8 plus Gen 1. Qualcomm states the upgraded model will offer 10% faster CPU performance, 10% faster GPU clocks, 30% power efficiency from both the CPU and GPU, 20% better AI performance per watt and 15% less power usage total. Additionally, following this announcement, Qualcomm also announced the new Snapdragon 7 gen 1 aimed at gamers with a 20% better graphics performance over the prior gen. Honor, Oppo and Xiaomi are the only brands listed as building devices around the 7 Gen 1, and are listed for release in the second quarter of 2022, whereas the 8 plus 1 gen devices are expected in the third quarter.


title: Qualcomm Snapdragon

text: Snapdragon system on chip products typically include a graphics processing unit (GPU), a global positioning system (GPS) and a cellular modem integrated into a single package. It has software included that operates graphics, video and picture-taking. There are 23 different Snapdragon processors under the 200, 400, 600, 700, and the 800 product families spanning from low to high-end respectively, as well as Wi-Fi and mobile charging products. Some of their components include the Adreno graphics processing, the Qualcomm Hexagon DSP and processors using Qualcomm's S4 processor architecture. In addition to smartphones, the 400 series is used in smart watches and the 602A is intended for electronics in cars.


title: Qualcomm Snapdragon

text: The current Snapdragon naming scheme was implemented after the Snapdragon 800 family was announced at the 2013 Consumer Electronics Show; prior models were renamed to the 200, 400 or 600 series. A new Snapdragon 600 was also released, which by mid-year was embedded in most new Android devices. The 400 family is entry-level, the 600 is mass-market or mid-range, and 800 family is for high-end or flagship phones.


title: Qualcomm Snapdragon

text: The Snapdragon 805 was released in November 2013. The 410, which is intended for low-cost phones in developing nations, was announced the following month. In January 2014, Qualcomm introduced a modified version of the Snapdragon 600 called 602A that is intended for in-car infotainment screens, backup cameras, and other driver assistance products. The quad-core Snapdragon 610 and eight-core 615 were announced in February 2014. The Snapdragon 808 and 810 were announced in April 2014. The Snapdragon 835, announced in November 2017, is the first Qualcomm SOC that is built on a 10 nm architecture. Qualcomm's new flagship chip for 2018, the 845, was announced in December 2017. According to Qualcomm, the 845 is 25-30% faster than the 835.


title: Qualcomm Snapdragon

text: In February 2015, Qualcomm re-branded its stand-alone modem products under the Snapdragon name; they were distinguished from SoCs using the "x" designation, such as the X7 or X12 modem. The first Snapdragon modem for 5G networks, the X50, was announced in October 2016. This was followed by the 2GBs X24 modem on a 7 nanometer manufacturing process that was announced in February 2018.


title: Qualcomm Snapdragon

text: According to CNET, Windows phones were growing in US market share and ranked highly in CNET reviews due to their responsiveness. Snapdragon SoCs are also used in most Windows phones and most phones entering the market in mid-2013. The LG G2 was the first phone to market using the Snapdragon 800 in August 2013.


title: Qualcomm Snapdragon

text: In 2017 the 660 and 630 replaced the 653 and 626 mid-range models and several chips in the 400 product family were revised. In February 2017, Qualcomm introduced the Snapdragon X20, intended for 5G cell phone networks, and two new chips for 802.11ax commercial Wi-Fi networks. This was followed by the addition of the 636 to the 600 product family that October, which Qualcomm said would be 40 percent faster than the 630.


title: Qualcomm Snapdragon

text: In August 2018, the Snapdragon 632, 439 and 429 were released. The new SoC is aimed at mid-range devices such as the Moto G6 Play, Huawei Honor 7A and Nokia 5.


title: Qualcomm Snapdragon

text: In December 2018, Qualcomm announced the 8cx at their Snapdragon Tech Summit 2018. The 8cx is Qualcomm's first SoC specifically designed for Always Connected PC (ACPC) platform. Unlike Qualcomm's past ACPC SoCs which were just their respective mobile SoCs at higher TDP. Qualcomm also showcased their Snapdragon X50 5G modem, Snapdragon 855 and QTM052 mmWave Antenna Module.


title: Qualcomm Snapdragon

text: In February 2019, Qualcomm announced their Snapdragon X55 5G modem, QTM525 mmWave antenna module, QET6100 envelope tracker and the new QAT3555 antenna impedance tuner.


title: Qualcomm Snapdragon

text: In July 2019, Qualcomm announced a refresh of the Snapdragon 855, the Snapdragon 855+, which is essentially an overclocked version of the 855 with both faster CPU and GPU performance.


title: Qualcomm Snapdragon

text: In December 2019, Qualcomm announced the Snapdragon X52 5G modem alongside the Snapdragon 765 and Snapdragon 865.


title: Qualcomm Snapdragon

text: Benchmark tests of the Snapdragon 800's processor by "PC Magazine" found that its processing power was comparable to similar products from Nvidia. Benchmarks of the Snapdragon 805 found that the Adreno 420 GPU resulted in a 40 percent improvement in graphics processing over the Adreno 330 in the Snapdragon 800, though there were only slight differences in processor benchmarks. Benchmarks of the Snapdragon 801 inside an HTC One found a "bump all around" in benchmark improvements over the 800. In 2015, Samsung's decision not to use the Snapdragon 810 in its Galaxy S6 had a significant detrimental impact on Snapdragon's revenues and reputation. Benchmark tests by Ars Technica confirmed rumors that the 810 under-performed lower-end models and had overheating issues. A Qualcomm spokesperson said these tests were done with early versions of the 810 that weren't ready for commercial use. An updated version was released and was found to moderately improve thermal throttling, GPU clock speeds, memory latency, and memory bandwidth when tested in a commercial product, the Xiaomi Mi Note Pro. Additionally, the 820/821, 835 and 845 performed substantially better. The Snapdragon 865's memory was improved in a later update. A 2019 benchmark test by PC World found that the 865's multi-core performance on the "default" setting was 30 percent higher than the 855 and comparable to the 855 Plus. The benchmark score for Snapdragon 888 released in 2021 is higher than that of the existing Snapdragon 865 Plus and Apple A13, but the heat output has increased by 60 percent.


title: Las Meninas

text: Las Meninas (; ) is a 1656 painting in the Museo del Prado in Madrid, by Diego Velázquez, the leading artist of the Spanish Golden Age. It has become one of the most widely analyzed works in Western painting, due to the way its complex and enigmatic composition raises questions about reality and illusion, and the uncertain relationship it creates between the viewer and the figures depicted.


title: Las Meninas

text: The painting is believed by F. J. Sánchez Cantón to depict a room in the Royal Alcazar of Madrid during the reign of King Philip IV of Spain, and presents several figures, most identifiable from the Spanish court, captured in a particular moment as if in a snapshot. Some of the figures look out of the canvas towards the viewer, while others interact among themselves. The five-year-old Infanta Margaret Theresa is surrounded by her entourage of maids of honour, chaperone, bodyguard, two dwarfs and a dog. Just behind them, Velázquez portrays himself working at a large canvas. Velázquez looks outwards, beyond the pictorial space to where a viewer of the painting would stand. In the background there is a mirror that reflects the upper bodies of the king and queen. They appear to be placed outside the picture space in a position similar to that of the viewer, although some scholars have speculated that their image is a reflection from the painting Velázquez is shown working on.


title: Las Meninas

text: "Las Meninas" has long been recognised as one of the most important paintings in the history of Western art. The Baroque painter Luca Giordano said that it represents the "theology of painting", and in 1827 the president of the Royal Academy of Arts Sir Thomas Lawrence described the work in a letter to his successor David Wilkie as "the true philosophy of the art". More recently, it has been described as "Velázquez's supreme achievement, a highly self-conscious, calculated demonstration of what painting could achieve, and perhaps the most searching comment ever made on the possibilities of the easel painting".


title: Las Meninas

text: In 17th-century Spain, painters rarely enjoyed high social status. Painting was regarded as a craft, not an art such as poetry or music. Nonetheless, Velázquez worked his way up through the ranks of the court of Philip IV, and in February 1651 was appointed palace chamberlain ("aposentador mayor del palacio"). The post brought him status and material reward, but its duties made heavy demands on his time. During the remaining eight years of his life, he painted only a few works, mostly portraits of the royal family. When he painted "Las Meninas", he had been with the royal household for 33 years.


title: Las Meninas

text: Philip IV's first wife, Elizabeth of France, died in 1644, and their only son, Balthasar Charles, died two years later. Lacking an heir, Philip married Mariana of Austria in 1649, and Margaret Theresa (1651–1673) was their first child, and their only one at the time of the painting. Subsequently, she had a short-lived brother Philip Prospero (1657–1661), and then Charles (1661–1700) arrived, who succeeded to the throne as Charles II at the age of three. Velázquez painted portraits of Mariana and her children, and although Philip himself resisted being portrayed in his old age he did allow Velázquez to include him in "Las Meninas". In the early 1650s he gave Velázquez the Pieza Principal ("main room") of the late Balthasar Charles's living quarters, by then serving as the palace museum, to use as his studio, where "Las Meninas" is set. Philip had his own chair in the studio and would often sit and watch Velázquez at work. Although constrained by rigid etiquette, the art-loving king seems to have had a close relationship with the painter. After Velázquez's death, Philip wrote "I am crushed" in the margin of a memorandum on the choice of his successor.


title: Las Meninas

text: During the 1640s and 1650s, Velázquez served as both court painter and curator of Philip IV's expanding collection of European art. He seems to have been given an unusual degree of freedom in the role. He supervised the decoration and interior design of the rooms holding the most valued paintings, adding mirrors, statues and tapestries. He was also responsible for the sourcing, attribution, hanging and inventory of many of the Spanish king's paintings. By the early 1650s, Velázquez was widely respected in Spain as a connoisseur. Much of the collection of the Prado today—including works by Titian, Raphael, and Rubens—were acquired and assembled under Velázquez's curatorship.


title: Las Meninas

text: The painting was referred to in the earliest inventories as "La Familia" ("The Family"). A detailed description of "Las Meninas", which provides the identification of several of the figures, was published by Antonio Palomino ("the Giorgio Vasari of the Spanish Golden Age") in 1724. Examination under infrared light reveals minor pentimenti, that is, there are traces of earlier working that the artist himself later altered. For example, at first Velázquez's own head inclined to his right rather than his left.


title: Las Meninas

text: The painting has been cut down on both the left and right sides. It was damaged in the fire that destroyed the Alcázar in 1734, and was restored by court painter Juan García de Miranda (1677–1749). The left cheek of the Infanta was almost completely repainted to compensate for a substantial loss of pigment. After its rescue from the fire, the painting was inventoried as part of the royal collection in 1747–48, and the Infanta was misidentified as Maria Theresa, Margaret Theresa's older half-sister, an error that was repeated when the painting was inventoried at the new Madrid Royal Palace in 1772. A 1794 inventory reverted to a version of the earlier title, "The Family of Philip IV", which was repeated in the records of 1814. The painting entered the collection of the Museo del Prado on its foundation in 1819. In 1843, the Prado catalogue listed the work for the first time as "Las Meninas".


title: Las Meninas

text: In recent years, the picture has suffered a loss of texture and hue. Due to exposure to pollution and crowds of visitors, the once-vivid contrasts between blue and white pigments in the costumes of the "meninas" have faded. It was last cleaned in 1984 under the supervision of the American conservator John Brealey, to remove a "yellow veil" of dust that had gathered since the previous restoration in the 19th century. The cleaning provoked, according to the art historian Federico Zeri, "furious protests, not because the picture had been damaged in any way, but because it looked different". However, in the opinion of López-Rey, the "restoration was impeccable". Due to its size, importance, and value, the painting is not lent out for exhibition.


title: Las Meninas

text: A thorough technical investigation including a pigment analysis of "Las Meninas" was conducted around 1981 in the Museo del Prado. The analysis revealed the usual pigments of the baroque period frequently used by Velázquez in his other paintings. The main pigments used for this painting were lead white, azurite (for the skirt of the kneeling menina), vermilion and red lake, ochres and carbon blacks.


title: Las Meninas

text: "Las Meninas" is set in Velázquez's studio in Philip IV's Alcázar palace in Madrid. The high-ceilinged room is presented, in the words of Silvio Gaggi, as "a simple box that could be divided into a perspective grid with a single vanishing point". In the centre of the foreground stands the Infanta Margaret Theresa (1). The five-year-old infanta, who later married Holy Roman Emperor Leopold I, was at this point Philip and Mariana's only surviving child. She is attended by two ladies-in-waiting, or "meninas": Doña Isabel de Velasco (2), who is poised to curtsy to the princess, and Doña  (3), who kneels before Margaret Theresa, offering her a drink from a red cup, or "búcaro", that she holds on a golden tray. To the right of the Infanta are two dwarfs: the achondroplastic German Mari Bárbola (4), and the Italian Nicolás Pertusato (5), who playfully tries to rouse a sleepy mastiff with his foot. The dog is thought to be descended from two mastiffs from Lyme Hall in Cheshire, given to Philip III in 1604 by James I of England. The Doña Marcela de Ulloa (6), the princess's chaperone, stands behind them, dressed in mourning and talking to an unidentified bodyguard (or "guardadamas") (7).


title: Las Meninas

text: To the rear and at right stands Don José Nieto Velázquez (8)—the queen's chamberlain during the 1650s, and head of the royal tapestry works—who may have been a relative of the artist. Nieto is shown standing but in pause, with his right knee bent and his feet on different steps. As the art critic Harriet Stone observes, it is uncertain whether he is "coming or going". He is rendered in silhouette and appears to hold open a curtain on a short flight of stairs, with an unclear wall or space behind. Both this backlight and the open doorway reveal space behind: in the words of the art historian Analisa Leppanen, they lure "our eyes inescapably into the depths". The royal couple's reflection pushes in the opposite direction, forward into the picture space. The vanishing point of the perspective is in the doorway, as can be shown by extending the line of the meeting of wall and ceiling on the right. Nieto is seen only by the king and queen, who share the viewer's point of view, and not by the figures in the foreground. In the footnotes of Joel Snyder's article, the author recognizes that Nieto is the queen's attendant and was required to be at hand to open and close doors for her. Snyder suggests that Nieto appears in the doorway so that the king and queen might depart. In the context of the painting, Snyder argues that the scene is the end of the royal couple's sitting for Velázquez and they are preparing to exit, explaining that is "why the menina to the right of the Infanta begins to curtsy".


title: Las Meninas

text: Velázquez himself (9) is pictured to the left of the scene, looking outward past a large canvas supported by an easel. On his chest is the red cross of the Order of Santiago, which he did not receive until 1659, three years after the painting was completed. According to Palomino, Philip ordered this to be added after Velázquez's death, "and some say that his Majesty himself painted it". From the painter's belt hang the symbolic keys of his court offices.


title: Las Meninas

text: A mirror on the back wall reflects the upper bodies and heads of two figures identified from other paintings, and by Palomino, as King Philip IV (10) and Queen Mariana (11). The most common assumption is that the reflection shows the couple in the pose they are holding for Velázquez as he paints them, while their daughter watches; and that the painting therefore shows their view of the scene.


title: Las Meninas

text: Of the nine figures depicted, five are looking directly out at the royal couple or the viewer. Their glances, along with the king and queen's reflection, affirm the royal couple's presence outside the painted space. Alternatively, art historians H. W. Janson and Joel Snyder suggest that the image of the king and queen is a reflection from Velázquez's canvas, the front of which is obscured from the viewer. Other writers say the canvas Velázquez is shown working on is unusually large for one of his portraits, and note that is about the same size as "Las Meninas". The painting contains the only known double portrait of the royal couple painted by the artist.


title: Las Meninas

text: The point of view of the picture is approximately that of the royal couple, though this has been widely debated. Many critics suppose that the scene is viewed by the king and queen as they pose for a double portrait, while the Infanta and her companions are present only to make the process more enjoyable. Ernst Gombrich suggested that the picture might have been the sitters' idea:


title: Las Meninas

text: Clark suggests that the work comprises a scene where the ladies-in-waiting are attempting to cajole the Infanta Doña Margarita to pose with her mother and father. In his 1960 book "Looking at Pictures", Clark writes:


title: Las Meninas

text: The back wall of the room, which is in shadow, is hung with rows of paintings, including one of a series of scenes from Ovid's "Metamorphoses" by Rubens, and copies, by Velázquez's son-in-law and principal assistant del Mazo, of works by Jacob Jordaens. The paintings are shown in the exact positions recorded in an inventory taken around this time. The wall to the right is hung with a grid of eight smaller paintings, visible mainly as frames owing to their angle from the viewer. They can be identified from the inventory as more Mazo copies of paintings from the Rubens Ovid series, though only two of the subjects can be seen.


title: Las Meninas

text: The paintings on the back wall are recognized as representing "Minerva Punishing Arachne" and "Apollo's Victory Over Marsyas". Both stories involve Minerva, the goddess of wisdom and patron of the arts. These two legends are both stories of mortals challenging gods and the dreadful consequences. One scholar points out that the legend dealing with two women, Minerva and Arachne, is on the same side of the mirror as the queen's reflection while the male legend, involving the god Apollo and the satyr Marsyas, is on the side of the king.


title: Las Meninas

text: The painted surface is divided into quarters horizontally and sevenths vertically; this grid is used to organise the elaborate grouping of characters, and was a common device at the time. Velázquez presents nine figures—eleven if the king and queen's reflected images are included—yet they occupy only the lower half of the canvas.


title: Las Meninas

text: According to López-Rey, the painting has three focal points: the Infanta Margaret Theresa, the self-portrait and the half-length reflected images of King Philip IV and Queen Mariana. In 1960, Clark observed that the success of the composition is a result first and foremost of the accurate handling of light and shade:


title: Las Meninas

text: However, the focal point of the painting is widely debated. Leo Steinberg argues that the orthogonals in the work are intentionally disguised so that the picture's focal center shifts. Similar to Lopez-Rey, he describes three foci. The man in the doorway, however, is the vanishing point. More specifically, the crook of his arm is where the orthogonals of the windows and lights of the ceiling meet.


title: Las Meninas

text: Depth and dimension are rendered by the use of linear perspective, by the overlapping of the layers of shapes, and in particular, as stated by Clark, through the use of tone. This compositional element operates within the picture in a number of ways. First, there is the appearance of natural light within the painted room and beyond it. The pictorial space in the midground and foreground is lit from two sources: by thin shafts of light from the open door, and by broad streams coming through the window to the right. The 20th-century French philosopher and cultural critic Michel Foucault observed that the light from the window illuminates both the studio foreground and the unrepresented area in front of it, in which the king, the queen, and the viewer are presumed to be situated. For José Ortega y Gasset, light divides the scene into three distinct parts, with foreground and background planes strongly illuminated, between which a darkened intermediate space includes silhouetted figures.


title: Las Meninas

text: Velázquez uses this light not only to add volume and definition to each form but also to define the focal points of the painting. As the light streams in from the right it brightly glints on the braid and golden hair of the female dwarf, who is nearest the light source. But because her face is turned from the light, and in shadow, its tonality does not make it a point of particular interest. Similarly, the light glances obliquely on the cheek of the lady-in-waiting near her, but not on her facial features. Much of her lightly coloured dress is dimmed by shadow. The Infanta, however, stands in full illumination, and with her face turned towards the light source, even though her gaze is not. Her face is framed by the pale gossamer of her hair, setting her apart from everything else in the picture. The light models the volumetric geometry of her form, defining the conic nature of a small torso bound rigidly into a corset and stiffened bodice, and the panniered skirt extending around her like an oval candy-box, casting its own deep shadow which, by its sharp contrast with the bright brocade, both emphasises and locates the small figure as the main point of attention.


title: Las Meninas

text: Velázquez further emphasises the Infanta by his positioning and lighting of her maids of honour, who are set opposite one another: before and behind the Infanta. The maid on the viewer's left is given a brightly lit profile, while her sleeve create a diagonal. Her opposite figure creates a broader but less defined reflection of her attention, making a diagonal space between them, in which their charge stands protected.


title: Las Meninas

text: A further internal diagonal passes through the space occupied by the Infanta. There is a similar connection between the female dwarf and the figure of Velázquez himself, both of whom look towards the viewer from similar angles, creating a visual tension. The face of Velázquez is dimly lit by light that is reflected, rather than direct. For this reason his features, though not as sharply defined, are more visible than those of the dwarf who is much nearer the light source. This appearance of a total face, full-on to the viewer, draws the attention, and its importance is marked, tonally, by the contrasting frame of dark hair, the light on the hand and brush, and the skilfully placed triangle of light on the artist's sleeve, pointing directly to the face.


title: Las Meninas

text: The mirror is a perfectly defined unbroken pale rectangle within a broad black rectangle. A clear geometric shape, like a lit face, draws the attention of the viewer more than a broken geometric shape such as the door, or a shadowed or oblique face such as that of the dwarf in the foreground or that of the man in the background. The viewer cannot distinguish the features of the king and queen, but in the opalescent sheen of the mirror's surface, the glowing ovals are plainly turned directly to the viewer. Jonathan Miller pointed out that apart from "adding suggestive gleams at the bevelled edges, the most important way the mirror betrays its identity is by disclosing imagery whose brightness is so inconsistent with the dimness of the surrounding wall that it can only have been borrowed, by reflection, from the strongly illuminated figures of the King and Queen".


title: Las Meninas

text: As the maids of honour are reflected in each other, so too do the king and queen have their doubles within the painting, in the dimly lit forms of the chaperone and guard, the two who serve and care for their daughter. The positioning of these figures sets up a pattern, one man, a couple, one man, a couple, and while the outer figures are nearer the viewer than the others, they all occupy the same horizontal band on the picture's surface.


title: Las Meninas

text: Adding to the inner complexities of the picture is the male dwarf in the foreground, whose raised hand echoes the gesture of the figure in the background, while his playful demeanour, and distraction from the central action, are in complete contrast with it. The informality of his pose, his shadowed profile, and his dark hair all serve to make him a mirror image to the kneeling attendant of the Infanta. However, the painter has set him forward of the light streaming through the window, and so minimised the contrast of tone on this foreground figure.


title: Las Meninas

text: Despite certain spatial ambiguities this is the painter's most thoroughly rendered architectural space, and the only one in which a ceiling is shown. According to López-Rey, in no other composition did Velázquez so dramatically lead the eye to areas beyond the viewer's sight: both the canvas he is seen painting, and the space beyond the frame where the king and queen stand can only be imagined. The bareness of the dark ceiling, the back of Velázquez's canvas, and the strict geometry of framed paintings contrast with the animated, brilliantly lit and sumptuously painted foreground entourage. Stone writes:


title: Las Meninas

text: According to Kahr, the composition could have been influenced by the traditional Dutch Gallery Pictures such as those by Frans Francken the Younger, Willem van Haecht, or David Teniers the Younger. Teniers' work was owned by Philip IV and would have been known by Velázquez. Like "Las Meninas", they often depict formal visits by important collectors or rulers, a common occurrence, and "show a room with a series of windows dominating one side wall and paintings hung between the windows as well as on the other walls". Gallery Portraits were also used to glorify the artist as well as royalty or members of the higher classes, as may have been Velázquez's intention with this work.


title: Las Meninas

text: The spatial structure and positioning of the mirror's reflection are such that Philip IV and Mariana appear to be standing on the viewer's side of the pictorial space, facing the Infanta and her entourage. According to Janson, not only is the gathering of figures in the foreground for Philip and Mariana's benefit, but the painter's attention is concentrated on the couple, as he appears to be working on their portrait. Although they can only be seen in the mirror reflection, their distant image occupies a central position in the canvas, in terms of social hierarchy as well as composition. As spectators, the viewer's position in relation to the painting is uncertain. It has been debated whether the ruling couple are standing beside the viewer or have replaced the viewer, who sees the scene through their eyes. Lending weight to the latter idea are the gazes of three of the figures—Velázquez, the Infanta, and Maribarbola—who appear to be looking directly at the viewer.


title: Las Meninas

text: The mirror on the back wall indicates what is not there: the king and queen, and in the words of Harriet Stone, "the generations of spectators who assume the couple's place before the painting". Writing in 1980, the critics Snyder and Cohn observed:


title: Las Meninas

text: In "Las Meninas", the king and queen are supposedly "outside" the painting, yet their reflection in the back wall mirror also places them "inside" the pictorial space.


title: Las Meninas

text: Snyder proposes it is "a mirror of majesty" or an allusion to the mirror for princes. While it is a literal reflection of the king and queen, Snyder writes "it is the image of exemplary monarchs, a reflection of ideal character". Later he focuses his attention on the princess, writing that Velázquez's portrait is "the painted equivalent of a manual for the education of the princess—a mirror of the princess".