which type of logic gate outputs the opposite of the input signal
Inverter (logic gate)


In digital logic, an inverter or NOT gate is a logic gate which implements logical negation. The truth table is shown on the right. An inverter circuit outputs a voltage representing the opposite logic-level to its input. Its main function is to invert the input signal applied. If the applied input is low then the output becomes high and vice versa. Inverters can be constructed using a single NMOS transistor or a single PMOS transistor coupled with a resistor. Since this 'resistive-drain' approach uses only a single
13127032
Diode logic


of producing simple logic functions without using additional logic gates. Most circuit families are designed to have compatible inputs and outputs depending on these signal levels to achieve reliable performance. Adding diode logic will degrade the signal level and result in poor noise rejection and possible failure. During the 1960s the use of tunnel diodes in logic circuits was an active research topic. When compared to transistor logic gates of the time, the tunnel diode offered much higher speeds. Unlike other diode types, the tunnel diode offered the possibility of amplification of signals
11059747
Diode logic


one input of every gate must be connected to a voltage level providing the defined logic 1 or logic 0 levels. If all the inputs are disconnected from any driving source the output signal is not confined to the correct voltage range. In logic gates, logical functions are performed by parallel or series connected switches (such as relay contacts or insulated gate FETs like CMOS) controlled by logical inputs or parallel resistors or diodes which are passive components. Diode logic is implemented by diodes which exhibit low impedance when forward biased and a very
11059728
Logic gate


identical to an "OR" function with negated inputs and outputs. Likewise, an "OR" function is identical to an "AND" function with negated inputs and outputs. A NAND gate is equivalent to an OR gate with negated inputs, and a NOR gate is equivalent to an AND gate with negated inputs. This leads to an alternative set of symbols for basic gates that use the opposite core symbol ("AND" or "OR") but with the inputs and outputs negated. Use of these alternative symbols
18487037
Molecular logic gate


can again be 0 or 1. The four output bit patterns that can arise corresponds to a specific logic type: PASS 0, YES, NOT and PASS 1. PASS 0 always outputs 0, whatever the input. PASS 1 always outputs 1, whatever the input. YES outputs a 1 when the input is 1 and NOT is the inverse YES – it outputs a 0 when the input is 1. An example of a YES logic gate is the molecular structure shown below. A "1" output is given only
9596593
NAND logic


delay four times (instead of three times) that of a single NAND gate. A multiplexer or a MUX gate is a three-input gate that uses one of the inputs, called the "selector bit," to select one of the other two inputs, called "data bits", and outputs only the selected data bit. A demultiplexer performs the opposite function of a multiplexer: It takes a single input and channels it to one of two possible outputs according to a selector bit that specifies which output to choose
4812415
State (computer science)


system to change its state. Examples of such systems are digital logic circuits and components, automata and formal language, computer programs, and computers. The output of a digital circuit or computer program at any time is completely determined by its current inputs and its state. Digital logic circuits can be divided into two types: combinational logic, whose output signals are dependent only on its present input signals, and sequential logic, whose outputs are a function of both the current inputs and the past history of inputs. In sequential logic
3212625
Logic gate


interest. The regular NAND symbol has a bubble at the output and none at the inputs (the opposite of the states that will turn the motor on), but the De Morgan symbol shows both inputs and output in the polarity that will drive the motor. De Morgan's theorem is most commonly used to implement logic gates as combinations of only NAND gates, or as combinations of only NOR gates, for economic reasons. Logic gates can also be used to store data. A storage element can be constructed by connecting several
18487041
Flip-flop (electronics)


and JK. The behavior of a particular type can be described by what is termed the characteristic equation, which derives the "next" (i.e., after the next clock pulse) output, in terms of the input signal(s) and/or the current output, formula_1. When using static gates as building blocks, the most fundamental latch is the simple "SR latch", where S and R stand for "set" and "reset". It can be constructed from a pair of cross-coupled NOR logic gates.
19335649
Nord Modular


of hardware modulars: audio input and output modules, Oscillators, Low Frequency Oscillators (or LFOs), envelopes, filters of various kinds, mixers, audio effects such as distortion and chorus, logic gates and four sequencer modules, which can be connected in almost any configuration- there is for example no restriction on connecting audio signal outputs to control signal or logic inputs (or vice versa), allowing for a great deal of flexibility in patch creation. Patches are only limited in complexity by the available DSP resources. However,
12082815
Sequential logic


clock pulses. At each cycle, the next state is determined by the current state and the value of the input signals when the clock pulse occurs. The main advantage of synchronous logic is its simplicity. The logic gates which perform the operations on the data require a finite amount of time to respond to changes to their inputs. This is called "propagation delay". The interval between clock pulses must be long enough so that all the logic gates have time to respond to the changes and their outputs "settle" to
6950906
Gate equivalent


a dedicated "standard cell library" is employed for each manufacturing technology (e.g., CMOS). The standard cell library comprises many different logic gates, for example a NAND gate. For each logical type of logic gate, e.g., a two-input NAND, there usually exist different physical realizations in the standard cell library, for instance with different output drive strengths. Basically, a two-input drive-strength-one NAND gate in CMOS technology consists of four transistors. If higher output drive strength is required,
19745826
Molecular logic gate


when sodium ions are present in solution ("1" input). Molecular logic gates work with input signals based on chemical processes and with output signals based on spectroscopy. One of the earlier water solution-based systems exploits the chemical behavior of compounds A and B in "scheme 1". Compound A is a push-pull olefin with the top receptor containing four carboxylic acid anion groups (and non-disclosed counter cations) capable of binding to calcium. The bottom part is a quinoline molecule which is a receptor
9596594
Adder (electronics)


this implementation, the final OR gate before the carry-out output may be replaced by an XOR gate without altering the resulting logic. Using only two types of gates is convenient if the circuit is being implemented using simple integrated circuit chips which contain only one gate type per chip. A full adder can also be constructed from two half adders by connecting "A" and "B" to the input of one half adder, then taking its sum-output "S" as one of the inputs to the second half
1831110
Fan-out


In digital electronics, the fan-out of a logic gate output is the number of gate inputs it can drive. In most designs, logic gates are connected to form more complex circuits. While no logic gate input can be fed by more than one output, it is common for one output to be connected to several inputs. The technology used to implement logic gates usually allows a certain number of gate inputs to be wired directly together without additional interfacing circuitry. The maximum fan-out of an output measures its load
4388251
Sequential logic


In digital circuit theory, sequential logic is a type of logic circuit whose output depends not only on the present value of its input signals but on the sequence of past inputs, the input history as well. This is in contrast to "combinational logic", whose output is a function of only the present input. That is, sequential logic has "state" ("memory") while combinational logic does not. Sequential logic is used to construct finite state machines, a basic building block in all digital circuitry.
6950901
Molecular logic gate


A molecular logic gate is a molecule that performs a logical operation based on one or more physical or chemical inputs and a single output. The field has advanced from simple logic systems based on a single chemical or physical input to molecules capable of combinatorial and sequential operations such as arithmetic operations i.e. moleculators and memory storage algorithms. For logic gates with a single input, there are four possible output patterns. When the input is 0, the output can be either a 0 or 1. When the input is 1, the output
9596592
Logic gate


flow (in either direction) between its input and its output. The semiconductor logic gate, on the other hand, acts as a high-gain voltage amplifier, which sinks a tiny current at its input and produces a low-impedance voltage at its output. It is not possible for current to flow between the output and the input of a semiconductor logic gate. Another important advantage of standardized integrated circuit logic families, such as the 7400 and 4000 families, is that they can be cascaded. This means that the
18487025
Logic gate


it is then called a sequential logic system since its output can be influenced by its previous state(s), i.e. by the "sequence" of input states. In contrast, the output from combinational logic is purely a combination of its present inputs, unaffected by the previous input and output states. These logic circuits are known as computer memory. They vary in performance, based on factors of speed, complexity, and reliability of storage, and many different types of designs are used based on the application. A three-state
18487043
Programmable logic array


A programmable logic array (PLA) is a kind of programmable logic device used to implement combinational logic circuits. The PLA has a set of programmable AND gate planes, which link to a set of programmable OR gate planes, which can then be conditionally complemented to produce an output. It has 2 AND Gates for N input variables, and for M outputs from PLA, there should be M OR Gates, each with programmable inputs from all of the AND gates. This layout allows for a large number of logic functions to
14037647
Noise-based logic


identifies the logic value at the input. The first gates analyzed the statistical correlations between the input signal and the reference noises. The advantage of these is the robustness against background noise. The disadvantage is the slow speed and higher hardware complexity. The instantaneous logic gates are fast, they have low complexity but they are not robust against background noises. With either neural spike type signals or with bipolar random-telegraph waves of unity absolute amplitude, and randomness only in the sign of the amplitude offer very simple instantaneous logic gates.
9793361
Molecular logic gate


parallel. The molecule mimics an electronic keypad of an automated teller machine (ATM). The output signals are dependent not only on the combination of inputs but also on the correct order of inputs: in other words the correct password must be entered. The molecule was designed using pyrene and fluorescein fluorophores connected by a siderophore, which binds to Fe(III), and the acidic of the solution changes the fluorescence properties of the fluorescein fluorophore. Further development in this field might also see molecular logic gates replace semiconductors in the IT industry
9596603
Flip-flop (electronics)


of the data input and force the output latch to stay in the corresponding state as the input logical zero (of the output stage) remains active while the clock is high. Hence the role of the output latch is to store the data only while the clock is low. The circuit is closely related to the gated D latch as both the circuits convert the two D input states (0 and 1) to two input combinations (01 and 10) for the output SR latch by inverting the data input signal (both
19335671
Quantum dot cellular automaton


such wires can form a complete set of logic gates for computation. There are two types of wires possible in QCA: A simple binary wire as shown in Figure 4 and an inverter chain, which is constituted by placing 45-degree inverted QCA cells side by side. Majority gate and inverter (NOT) gate are considered as the two most fundamental building blocks of QCA. Figure 5 shows a majority gate with three inputs and one output. In this structure, the electrical field effect of each input on the output is identical and
9982363
Photochemical logic gate


a low (non-radiative decay) of the energy The alternatives for producing an AND gate, using molecular photphysics, are two. (1) The emission produced by the electron drop from C*→C () is not a valid output frequency. The emission from the C** ( + , ) molecular orbital is a valid output signal;. to be used in subsequent logic gates -arranged to respond to the formula_1 emission. The second input of photon(s) to trigger the rapid conversion of a molecule used to complete the
13735811
Asynchronous circuit


have advantages in lower power consumption, lower electromagnetic interference, and better modularity in large systems. Asynchronous circuits are an active area of research in digital logic design. Digital logic circuits can be divided into combinational logic, in which the output signals depend only on the current input signals, and sequential logic, in which the output depends both on current input and on past inputs. In other words, sequential logic is combinational logic with memory. Virtually all practical digital devices require sequential logic. Sequential logic can be divided into two
3579021
NAND gate


In digital electronics, a NAND gate (NOT-AND) is a logic gate which produces an output which is false only if all its inputs are true; thus its output is complement to that of an AND gate. A LOW (0) output results only if all the inputs to the gate are HIGH (1); if any input is LOW (0), a HIGH (1) output results. A NAND gate is made using transistors and junction diodes. By De Morgan's theorem, a two
6906213
NOR logic


A NOR gate is a logic gate which gives a positive output only when both inputs are negative. Like NAND gates, NOR gates are so-called "universal gates" that can be combined to form any other kind of logic gate. For example, the first embedded system, the Apollo Guidance Computer, was built exclusively from NOR gates, about 5,600 in total for the later versions. Today, integrated circuits are not constructed exclusively from a single type of gate. Instead, EDA tools are used to convert the description
16738058
Cis-regulatory module


. The output of each module is a product of the various operations performed on it. Common operations include "OR" logic gate – This design indicates that in an output will be given when either input is given [3]. "AND" logic gate – In this design two different regulatory factors are necessary to make sure that a positive output results. "Toggle Switches" – This design occurs when the signal ligand is absent while the transcription factor is present; this transcription factor ends up acting as a dominant repressor
5001046
Diode logic


of the 1962 D-17B used diode-resistor logic as much as possible, to minimize the number of transistors used. Digital logic implemented by active elements is characterized by signal restoration. "True" and "false" or "1" and "0" are represented by two specific voltage levels. If the inputs to a digital logic gate is close to their respective levels, the output will be closer or exactly equal to its desired level. Active logic gates may be integrated in large numbers because each gate tends to remove
11059745
Wired logic connection


ground in the OR connection. Also, notice the positioning of the diodes as compared to the AND gate. Similarly, the OR connection is capable of an arbitrary number of inputs and only one output. The output "C" is determined by the inputs at "A" and "B" according to the truth table (not shown) and square wave (below). A wired AND can be converted into a wired OR, and vice versa, by using signals with reversed levels. Common examples are signals like
13196796
Flip-flop (electronics)


the circuits split the single D signal in two complementary S and R signals). The difference is that in the gated D latch simple NAND logical gates are used while in the positive-edge-triggered D flip-flop SR NAND latches are used for this purpose. The role of these latches is to "lock" the active output producing low voltage (a logical zero); thus the positive-edge-triggered D flip-flop can also be thought of as a gated D latch with latched input gates.
19335672
Logical effort


transistors such that the output drive of the gate is equal to the output drive of an inverter built from a size-2 PMOS and a size-1 NMOS. The output drive of a gate is equal to the minimum – over all possible combinations of inputs – of the output drive of the gate for that input. The output drive of a gate for a given input is equal to the drive at its output node. The drive at a node is equal to the sum of the drives of all transistors which are enabled and whose source
14908859
Race condition


effect, the temporary glitch becomes a permanent glitch). Consider, for example, a two-input AND gate fed with a logic signal A on one input and its negation, NOT A, on another input. In theory the output (A AND NOT A) should never be true. If, however, changes in the value of A take longer to propagate to the second input than the first when A changes from false to true then a brief period will ensue during which both inputs are true, and so
13645564
Binary decoder


In digital electronics, a binary decoder is a combinational logic circuit that converts binary information from the n coded inputs to a maximum of 2 unique outputs. They are used in a wide variety of applications, including data demultiplexing, seven segment displays, and memory address decoding. There are several types of binary decoders, but in all cases a decoder is an electronic circuit with multiple input and multiple output signals, which converts every unique combination of input states to a specific combination of output states. In addition to integer data inputs
12410004
NAND logic


the output will be 0. To be an OR gate, however, the output must be 1 if any input is 1. Therefore, if the inputs are inverted, any high input will trigger a high output. A NOR gate is an OR gate with an inverted output. Output is high when neither input A nor input B is high. An XOR gate is made by connecting four NAND gates as shown below. This construction entails a propagation delay three times that of a single NAND gate. Alternatively, the B
4812413
Counter (digital)


In digital logic and computing, a counter is a device which stores (and sometimes displays) the number of times a particular event or process has occurred, often in relationship to a clock signal. The most common type is a sequential digital logic circuit with an input line called the "clock" and multiple output lines. The values on the output lines represent a number in the binary or BCD number system. Each pulse applied to the clock input increments or decrements the number in the counter. A counter circuit is usually
7879393
AND gate


The AND gate is a basic digital logic gate that implements logical conjunction - it behaves according to the truth table to the right. A HIGH output (1) results only if all the inputs to the AND gate are HIGH (1). If none or not all inputs to the AND gate are HIGH, a LOW output results. The function can be extended to any number of inputs. There are three symbols for AND gates: the American (ANSI or 'military') symbol and the IEC ('European
11825352
Soft error


path gate inputs prevent a logical transition of that gate's output. An SEU is "electrically masked" if the signal is attenuated by the electrical properties of gates on its propagation path such that the resulting pulse is of insufficient magnitude to be reliably latched. An SEU is "temporally masked" if the erroneous pulse reaches an output latch, but it does not occur close enough to when the latch is actually triggered to hold. If all three masking effects fail to occur, the propagated pulse becomes latched and the output of
13373761
Triple modular redundancy


output. The majority gate output is 1 if two or more of the inputs of the majority gate are 1; output is 0 if two or more of the majority gate’s inputs are 0. The majority logic gate is a simple AND–OR circuit: if the inputs to the majority gate are denoted by x, y and z, then the output of the majority gate is Thus, the majority gate is the carry output of a full adder, i.e., the majority gate is a voting machine. Truth table
4406702
Dynamic logic (digital electronics)


write to a register to set a binary latch bit which would be ANDed or ORed with the processor clock, stopping the processor. A signal from a peripheral device would reset this latch, resuming CPU operation. [The hardware logic must gate the latch control inputs as necessary to ensure that a latch output transition does not cause the clock signal level to instantaneously change and cause a clock pulse, either high or low, that is shorter than normal.]) In particular, although many popular CPUs use dynamic logic, only
3536181
NOR gate


The NOR gate is a digital logic gate that implements logical NOR - it behaves according to the truth table to the right. A HIGH output (1) results if both the inputs to the gate are LOW (0); if one or both input is HIGH (1), a LOW output (0) results. NOR is the result of the negation of the OR operator. It can also be seen as an AND gate with all the inputs inverted. NOR is a functionally complete operation—NOR gates can
4864989
Race condition


race condition may occur when a logic gate combines signals that have traveled along different paths from the same source. The inputs to the gate can change at slightly different times in response to a change in the source signal. The output may, for a brief period, change to an unwanted state before settling back to the designed state. Certain systems can tolerate such glitches but if this output functions as a clock signal for further systems that contain memory, for example, the system can rapidly depart from its designed behaviour (in
13645563
Sequential logic


for a clock signal to process inputs. The speed of the device is potentially limited only by the propagation delays of the logic gates used. However, asynchronous logic is more difficult to design and is subject to problems not encountered in synchronous designs. The main problem is that digital memory elements are sensitive to the order that their input signals arrive; if two signals arrive at a flip-flop or latch at almost the same time, which state the circuit goes into can depend on which signal gets to the gate first.
6950908
Molecular logic gate


groups, when attached to anthracene can simultaneously process information concerning acid concentration and oxidizing ability of the solution. The INHIBIT logic gate illustrated below as provided by Gunnlaugsson et al. incorporates a Tb ion in a chelate complex. This two-input logic gate is the first of its kind and displays non-commutative behaviour with chemical inputs and a phosphorescence output. Whenever dioxygen (input 1) is present, the system is quenched and no phosphorescence is observed (output 0). The second input, H, must also be
9596600
Phase detector


system sensitivity." since it does not create finite pulse widths at the phase detector output. Another advantage of a mixer-based PD is its relative simplicity. Both the quadrature and simple multiplier phase detectors have an output that depends on the input amplitudes as well as the phase difference. In practice, the input amplitudes are normalized. A phase detector suitable for square wave signals can be made from an exclusive-OR (XOR) logic gate. When the two signals being compared are completely in-phase, the XOR
4223475
Toffoli gate


In logic circuits, the Toffoli gate (also CCNOT gate), invented by Tommaso Toffoli, is a universal reversible logic gate, which means that any reversible circuit can be constructed from Toffoli gates. It is also known as the "controlled-controlled-not" gate, which describes its action. It has 3-bit inputs and outputs; if the first two bits are both set to 1, it inverts the third bit, otherwise all bits stay the same. An input-consuming logic gate "L" is reversible
10060
Positive feedback


feedback. While normal simple boolean logic gates usually rely simply on gain to push digital signal voltages away from intermediate values to the values that are meant to represent boolean '0' and '1', but many more complex gates use feedback. When an input voltage is expected to vary in an analogue way, but sharp thresholds are required for later digital processing, the Schmitt trigger circuit uses positive feedback to ensure that if the input voltage creeps gently above the threshold, the output is forced smartly and rapidly from one logic
2037902
Logical effort


or drain is in contact with the node in question. A PMOS transistor is enabled when its gate voltage is 0. An NMOS transistor is enabled when its gate voltage is 1. Once sizes have been chosen, the logical effort of the output of the gate is the sum of the widths of all transistors whose source or drain is in contact with the output node. The logical effort of each input to the gate is the sum of the widths of all transistors whose gate is in contact with that input node. The
14908860
AND gate


' or 'rectangular') symbol, as well as the deprecated DIN symbol. Additional inputs can be added as needed. For more information see Logic Gate Symbols. The AND gate with inputs "A" and "B" and output "C" implements the logical expression formula_1. An AND gate is usually designed using N-channel (pictured) or P-channel MOSFETs. The digital inputs a and b cause the output F to have the same result as the AND function. formula_2 is the analytical representation of
11825353
Fan-out


of the manufacturer's given fan-out number. However, for any reputable manufacturer, if this current analysis reveals that the device cannot drive the inputs, the fan-out number will agree. When high-speed signal switching is required, the AC impedance of the output, the inputs, and the conductors between may significantly reduce the effective drive capacity of output, and this DC analysis may not be enough. See "AC Fan-out" below. A perfect logic gate would have infinite input impedance and
4388256
Pass transistor logic


at its output than at its input. If several devices are chained in series in a logic path, a conventionally constructed gate may be required to restore the signal voltage to the full value. By contrast, conventional CMOS logic switches transistors so the output connects to one of the power supply rails, so logic voltage levels in a sequential chain do not decrease. Simulation of circuits may be required to ensure adequate performance. Pass transistor logic often uses fewer transistors, runs faster, and requires less power than the same function implemented
264508
Verilog


to real gates. The next interesting structure is a transparent latch; it will pass the input to the output when the gate signal is set for "pass-through", and captures the input and stores it upon transition of the gate signal to "hold". The output will remain stable regardless of the input signal while the gate is set to "hold". In the example below the "pass-through" level of the gate would be when the value of the if clause is true, i.e. gate
16794852
Logic gate


and the polarity of its nodes that are considered in the "signaled" (active, on) state. Consider the simplified case where a two-input NAND gate is used to drive a motor when either of its inputs are brought low by a switch. The "signaled" state (motor on) occurs when either one OR the other switch is on. Unlike a regular NAND symbol, which suggests AND logic, the De Morgan version, a two negative-input OR gate, correctly shows that OR is of
18487040
XNOR gate


The XNOR gate (sometimes ENOR, EXNOR or NXOR and pronounced as Exclusive NOR) is a digital logic gate whose function is the logical complement of the exclusive OR (XOR) gate. The two-input version implements logical equality, behaving according to the truth table to the right, and hence the gate is sometimes called an "equivalence gate". A high output (1) results if both of the inputs to the gate are the same. If one but not both inputs are high (1), a
4812535
Programmable logic device


programmable logic array for this device. A programmable logic array (PLA) has a programmable AND gate array, which links to a programmable OR gate array, which can then be conditionally complemented to produce an output. PAL devices have arrays of transistor cells arranged in a "fixed-OR, programmable-AND" plane used to implement "sum-of-products" binary logic equations for each of the outputs in terms of the inputs and either synchronous or asynchronous feedback from the outputs. MMI introduced a breakthrough device in
21616114
XOR gate


XOR gate (sometimes EOR, or EXOR and pronounced as Exclusive OR) is a digital logic gate that gives a true (1 or HIGH) output when the number of true inputs is odd. An XOR gate implements an exclusive or; that is, a true output results if one, and only one, of the inputs to the gate is true. If both inputs are false (0/LOW) or both are true, a false output results. XOR represents the inequality function, i.e., the output is
4811954
Delay-insensitive minterm synthesis


C-elements and then gathering the outputs of these using OR gates which generate the true and false output signals. With two dual-rail inputs the gate would be composed of four two-input C-elements. A three input gate uses eight three-input C-elements. Latches are constructed using two C-elements to store the data and an OR gate to acknowledge the input once the data has been latched by attaching as its inputs the data output wires. The acknowledge from the forward stage is inverted and
12211790
Incremental encoder


This type of receiver rejects common-mode noise and converts the incoming differential signals to the single-ended form required by downstream logic circuits. In mission-critical systems, an encoder interface may be required to detect loss of input signals due to encoder power loss, signal driver failure, cable fault or cable disconnect. This is usually accomplished by using enhanced RS-422 line receivers which detect the absence of valid input signals and report this condition via a "signal lost" status output. In normal operation, glitches (brief pulses
8477468
Transistor–transistor logic


may be useful to convert analog signals to the digital domain but would not ordinarily be used where analog amplification is the primary purpose. TTL inverters can also be used in crystal oscillators where their analog amplification ability is significant. A TTL gate may operate inadvertently as an analog amplifier if the input is connected to a slowly changing input signal that traverses the unspecified region from 0.8 V to 2 V. The output can be erratic when the input is in this range. A slowly changing input like this can also cause excess power dissipation in
3506364
Logic gate


in input of a gate to the corresponding change in its output. When gates are cascaded, the total propagation delay is approximately the sum of the individual delays, an effect which can become a problem in high-speed circuits. Additional delay can be caused when a large number of inputs are connected to an output, due to the distributed capacitance of all the inputs and wiring and the finite amount of current that each output can provide. The binary number system was refined by Gottfried Wilhelm Leibniz (published in 1705),
18487027
Combinational logic


In digital circuit theory, combinational logic (sometimes also referred to as time-independent logic ) is a type of digital logic which is implemented by Boolean circuits, where the output is a pure function of the present input only. This is in contrast to sequential logic, in which the output depends not only on the present input but also on the history of the input. In other words, sequential logic has "memory" while combinational logic does not. Combinational logic is used in computer circuits to perform Boolean algebra on
6950889
Internet Radio Linking Project


. MT8870 pin 15 provides a pulse when any valid DTMF digit is decoded, so this signal is used on one input of each gate on the HCF4081. The other gate input is from MT8870 pins 11,12,13,14. The output of the HCF4081 (pins 3,4,10,11) connect to the parallel port and provide the pulsed input that IRLP needs. The IRLP software cannot decode the D digit (the bottom right key on a 16-button DTMF dial). This is a limitation of the hardware in the decoder. DTMF digit D is logic
14642968
OR gate


The OR gate is a digital logic gate that implements logical disjunctionit behaves according to the truth table to the right. A HIGH output (1) results if one or both the inputs to the gate are HIGH (1). If neither input is high, a LOW output (0) results. In another sense, the function of OR effectively finds the "maximum" between two binary digits, just as the complementary AND function finds the "minimum". There are two symbols of OR gates: the American (
11825361
Incremental encoder


serve as buffers to protect downstream interface circuitry and, in many cases, also provide signal conditioning functions. Incremental encoder interfaces typically employ Schmitt trigger inputs to receive signals from encoders that have single-ended (e.g., push-pull, open collector) outputs. This type of line receiver inherently rejects low-level noise (by means of its input hysteresis) and protects downstream circuitry from invalid (and possibly destructive) logic signal levels. RS-422 line receivers are commonly used to receive signals from encoders that have differential outputs.
8477467
Molecular logic gate


a high fluorescence. The specific concentration threshold of each input must be reached to achieve a fluorescent output in accordance with combinatorial AND logic. This prototype could potentially be extended to point-of-care medical diagnostics application for disease screening in the future. In a similar set-up, the molecular logic gate illustrated below demonstrates the advancement from redox-fluorescent switches to multi-input logic gates with an electrochemical switch. This two-input AND logic gate incorporates a tertiary amine proton receptor and a tetrathiafulvelene redox donor. These
9596599
NOR logic


the NOR gate, eliminating it from consideration and leaving only the NOT part. An OR gate is made by inverting the output of a NOR gate. Note that we already know that a NOT gate is equivalent to a NOR gate with its inputs joined. An AND gate gives a 1 output when both inputs are 1.Therefore, an AND gate is made by inverting the inputs of a NOR gate. Again, note that a NOT gate is equivalent to a NOR with its inputs joined. A NAND gate is made by inverting
16738060
Fan-out


-driving capability: it is the greatest number of inputs of gates of the same type to which the output can be safely connected. Maximum limits on fan-out are usually stated for a given logic family or device in the manufacturer's datasheets. These limits assume that the driven devices are members of the same family. More complex analysis than fan-in and fan-out is required when two different logic families are interconnected. Fan-out is ultimately determined by the maximum source and sink currents of an output and
4388252
Wired logic connection


A" and "B" via the diodes connected directed towards the inputs. When positive logic that is equal to or greater than that of the source is applied to all inputs the source voltage is directed to the output. The AND gate is capable of an arbitrary number of inputs. The wired AND function can be achieved by simply tying gate outputs together to a common-collector pull-up resistor. The wired AND function below is achieved by using open collector TTL gates. This is commonly called Dot OR. The
13196794
Fan-out


zero output impedance, allowing a gate output to drive any number of gate inputs. However, since real-world fabrication technologies exhibit less than perfect characteristics, a limit will be reached where a gate output cannot drive any more current into subsequent gate inputs - attempting to do so causes the voltage to fall below the level defined for the logic level on that wire, causing errors. The fan-out is simply the number of inputs that can be connected to an output before the current required by the inputs exceeds the
4388257
Wired logic connection


output "C" is determined by the inputs at "A" and "B" according to the truth table (right). The wired OR connection electrically performs the Boolean logic operation of an OR gate, using a pull down resistor and one diode per input. Voltage from any input is directed through its corresponding diode directly to the output "C". If no voltage/logic exists on any input there will be no output. The positive voltage source that is present in the AND connection is replaced by a
13196795
Integrated injection logic


current is not shunted to ground because the input is high-z (high logic level), the bias current flows through the transistor to the emitter, switching on the transistor, and allowing the collector to sink current (low logic level). Because the output of the inverter can sink current but cannot source current, it is safe to connect the outputs of multiple inverters together to form a wired AND gate. When the outputs of two inverters are wired together, the result is a two-input NOR gate
15088983
Transistor–transistor logic


is needed to drive an input into an undefined region. In some cases (e.g., when the output of a TTL logic gate needs to be used for driving the input of a CMOS gate), the voltage level of the "totem-pole" output stage at output logical "1" can be increased closer to V by connecting an external resistor between the V collector and the positive rail. It pulls up the V cathode and cuts-off the diode. However, this technique actually converts the sophisticated "totem
3506354
Direct-coupled transistor logic


Direct-coupled transistor logic (DCTL) is similar to resistor–transistor logic (RTL) but the input transistor bases are connected directly to the collector outputs without any base resistors. Consequently, DCTL gates have fewer components, are more economical, and are simpler to fabricate onto integrated circuits than RTL gates. Unfortunately, DCTL has much smaller signal levels, has more susceptibility to ground noise, and requires matched transistor characteristics. The transistors are also heavily overdriven; that is a good feature in that it reduces the saturation voltage
11791775
Fault tree analysis


the set operations of Boolean logic. The probability of a gate's output event depends on the input event probabilities. An AND gate represents a combination of independent events. That is, the probability of any input event to an AND gate is unaffected by any other input event to the same gate. In set theoretic terms, this is equivalent to the intersection of the input event sets, and the probability of the AND gate output is given by: An OR gate, on the other hand, corresponds to set union:
20596846
Hot spare


, receiving the same set of inputs, performing identical computations and producing identical outputs in a nearly-synchronous manner. The outputs are typically physical outputs (individual ON/OFF type digital signals, or analog signals), or serial data messages wrapped in suitable protocols depending upon the nature of their intended use. Outputs from only one unit (designated as the master or on-line unit, via application logic) are used to control external devices (such as switches, signals, on-board propulsion/braking control devices
7654266
Pass transistor logic


gates that uses transmission gates composed of both NMOS and PMOS pass transistors. Other authors use the term "complementary pass transistor logic" (CPL) to indicate a style of implementing logic gates where each gate consists of a NMOS-only pass transistor network, followed by a CMOS output inverter. Other authors use the term "complementary pass transistor logic" (CPL) to indicate a style of implementing logic gates using dual-rail encoding. Every CPL gate has two output wires, both the positive signal and the complementary signal
264511
Reversible computing


terms of gate-level circuits. A simplified model of such circuits is one in which inputs are consumed (however, note that real logic gates as implemented e.g. in CMOS do not do this). In this modeling framework, an inverter (logic gate) (NOT) gate is reversible because it can be "undone". The exclusive or (XOR) gate is irreversible because its two inputs cannot be unambiguously reconstructed from its single output. However, a reversible version of the XOR gate—the controlled NOT
14077668
Sequential logic


Therefore, the circuit can go into the wrong state, depending on small differences in the propagation delays of the logic gates. This is called a race condition. This problem is not as severe in synchronous circuits because the outputs of the memory elements only change at each clock pulse. The interval between clock signals is designed to be long enough to allow the outputs of the memory elements to "settle" so they are not changing when the next clock comes. Therefore, the only timing problems are due to "asynchronous inputs
6950909
NMOS logic


NOR gate implemented in schematic NMOS. If either input A or input B is high (logic 1, = True), the respective MOS transistor acts as a very low resistance between the output and the negative supply, forcing the output to be low (logic 0, = False). When both A and B are high, both transistors are conductive, creating an even lower resistance path to ground. The only case where the output is high is when both transistors are off, which occurs only when both A and
4761480
Molecular machine


constructed from DNA and are considered DNA machines. A molecular sensor is a molecule that interacts with an analyte to produce a detectable change. Molecular sensors combine molecular recognition with some form of reporter, so the presence of the item can be observed. A molecular logic gate is a molecule that performs a logical operation on one or more logic inputs and produces a single logic output. Unlike a molecular sensor, the molecular logic gate will only output when a particular combination of inputs are present. A molecular assembler is a molecular machine
18629707
Resistor–transistor logic


being the limit for many circuit designs, before it completely loses usable noise immunity. It has a low noise margin. Lancaster says that integrated circuit RTL NOR gates (which have one transistor per input) may be constructed with "any reasonable number" of logic inputs, and gives an example of an 8-input NOR gate. A standard integrated circuit RTL NOR gate can drive up to 3 other similar gates. Alternatively, it has enough output to drive up to 2 standard integrated circuit RTL "buffers", each of which
21441821
Boolean algebra


low reverses this. The line on the right of each gate represents the output port, which normally follows the same voltage conventions as the input ports. Complement is implemented with an inverter gate. The triangle denotes the operation that simply copies the input to the output; the small circle on the output denotes the actual inversion complementing the input. The convention of putting such a circle on any port means that the signal passing through this port is complemented on the way through, whether it is an input or output port. The
12666165
XNOR gate


not strictly true with XOR and XNOR gates. However, extending the concept of the binary logical operation to three inputs, the SN74S135 with two shared "C" and four independent "A" and "B" inputs for its four outputs, was a device that followed the truth table: Note that this is effectively Y = NOT ((A XOR B) XOR C). Another way to interpret this is that the output is true if an even number of inputs are true. It does not implement a logical
4812540
NOR logic


the output of an AND gate. An XNOR gate is made by connecting four NOR gates as shown below. This construction entails a propagation delay three times that of a single NOR gate. Alternatively, the B-input of the XOR gate with the 3-gate propagation delay can be inverted. This construction uses five gates instead of four. An XOR gate is made by connecting the output of 3 NOR gates (connected as an AND gate) and the output of a NOR gate to the respective inputs of a NOR gate.
16738061
Ring oscillator


A ring oscillator is a device composed of an odd number of NOT gates in a ring, whose output oscillates between two voltage levels, representing "true" and "false". The NOT gates, or inverters, are attached in a chain and the output of the last inverter is fed back into the first. Because a single inverter computes the logical NOT of its input, it can be shown that the last output of a chain of an odd number of inverters is the logical NOT of the first input. The
20144483
Diode logic


noise at its input. Diode logic gates are implemented by passive elements; so, they have two restoration problems. Diode logic gates are used to build diode–transistor logic (DTL) gates as integrated circuits. The outputs of conventional ICs (with complementary output drive stages) are never directly connected together since they act as voltage sources. However, diodes can be used to combine two or more digital (high/low) outputs from an IC such as a counter. This wired logic connection can be a useful way
11059746
1-Wire


pass it on. Software can therefore explore sequential "bus domains". The following signals were generated by an FPGA, which was the master for the communication with a DS2432 (EEPROM) chip, and measured with a logic analyzer. A logic high on the 1-wire output, means the output of the FPGA is in tri-state mode and the 1-wire device can pull the bus low. A low means the FPGA pulls down the bus. The 1-wire input is the measured bus signal. On input sample time high,
7738845
XOR gate


it would in effect be a one-hot detector (and indeed this is the case for only two inputs). However, it is rarely implemented this way in practice. It is most common to regard subsequent inputs as being applied through a cascade of binary exclusive-or operations: the first two signals are fed into an XOR gate, then the output of that gate is fed into a second XOR gate together with the third signal, and so on for any remaining signals. The result is a circuit that outputs
4811962
Synaptic gating


provides the input signal and the other provides the output signal. It is the role of the gatekeeper neuron to regulate the transmission of the input to the output. When activated, the gatekeeper neuron alters the polarity of the presynaptic axon to either open or close the gate. If this neuron depolarizes the presynaptic axon, it allows the signal to be transmitted. Thus, the gate is open. Hyperpolarization of the presynaptic axon closes the gate. Just like in a transistor, the gatekeeper neuron turns the system on or off;
9371598
Pull-up resistor


as the voltage changes in an RC circuit), but will draw more current. A resistor with relatively high resistance is called a "weak" pull-up or pull-down; when the circuit is open, it will pull the output high or low more slowly, but will draw less current. A pull-up resistor may be used when interfacing logic gates to inputs. For example, an input signal may be pulled by a resistor, then a switch or jumper strap can be used to connect that input
3700249
Emitter-coupled logic


Yourke. Originally called "current-steering logic", it was used in the Stretch, IBM 7090, and IBM 7094 computers. The logic was also called a current-mode circuit. It was also used to make the ASLT circuits in the IBM 360/91. Yourke's current switch was a differential amplifier whose input logic levels were different from the output logic levels. "In current mode operation, however, the output signal consists of voltage levels which vary about a reference level different from the input reference level."
21946941
Flip-flop (electronics)


the latching action, the inputs are considered to be inverted in this circuit (or active low). The circuit uses feedback to "remember" and retain its logical state even after the controlling input signals have changed. When the S and R inputs are both high, feedback maintains the Q outputs to the previous state. From the teaching point of view, SR latches realised as a pair of cross-coupled components (transistors, gates, tubes, etc.) are rather hard to understand for beginners. A didactically
19335654
Directed acyclic graph


leaves the element through its outgoing edges. For instance, in electronic circuit design, static combinational logic blocks can be represented as an acyclic system of logic gates that computes a function of an input, where the input and output of the function are represented as individual bits. In general, the output of these blocks cannot be used as the input unless it is captured by a register or state element which maintains its acyclic properties. Electronic circuit schematics either on paper or in a database are a form of directed acyclic graphs
21677872
Multiplexer


ends of a transmission link because most communications systems transmit in both directions. In analog circuit design, a multiplexer is a special type of analog switch that connects one signal selected from several inputs to a single output. In digital circuit design, the selector wires are of digital value. In the case of a 2-to-1 multiplexer, a logic value of 0 would connect formula_4 to the output while a logic value of 1 would connect formula_5 to the output. In larger multiplexers, the number of selector pins is equal to formula_6 where
17629803
Toffoli gate


if, for any output "y", there is a unique input "x" such that applying "L"("x") = "y". If a gate "L" is reversible, there is an inverse gate "L"′, which maps "y" to "x" for which "L"′("y") = "x". From common logic gates, NOT is reversible, as can be seen from its truth table below. The common AND gate is not reversible, however. The inputs 00, 01
10061
NAND logic


-input of the XNOR gate with the 3-gate propagation delay can be inverted. This construction uses five gates instead of four. An XNOR gate is made by connecting the output of 3 NAND gates (connected as an OR gate) and the output of a NAND gate to the respective inputs of a NAND gate. This construction entails a propagation delay three times that of a single NAND gate and uses five gates. Alternatively, the 4-gate version of the XOR gate can be used with an inverter. This construction has a propagation
4812414
Transistor–transistor logic


at output logical "1" that is completely determined by the output collector resistor. It limits the number of inputs that can be connected (the fanout). Some advantage of the simple output stage is the high voltage level (up to V) of the output logical "1" when the output is not loaded. A common variation omits the collector resistor of the output transistor, making an open-collector output. This allows the designer to fabricate logic by connecting the open-collector outputs of several logic gates together
3506344
Don't-care term


In digital logic, a don't-care term for a function is an input-sequence (a series of bits) for which the function output does not matter. An input that is known never to occur is a can't-happen term. Both these types of conditions are treated the same way in logic design and may be referred to collectively as "don't-care conditions" for brevity. The designer of a logic circuit to implement the function need not care about such inputs, but can choose the circuit's output
2219107
NOR gate


families, NOR gates were efficient and most commonly used. The diagrams above show the construction of a 2-input NOR gate using NMOS logic circuitry. If either of the inputs is high, the corresponding N-channel MOSFET is turned on and the output is pulled low; otherwise the output is pulled high through the pull-up resistor. The diagram below shows a 2-input NOR gate using CMOS technology. The diodes and resistors on the inputs are to protect the CMOS components from damage due to electrostatic discharge (ESD) and play
4864993