An Integrated IF Amplifier and Detector for an A.M. Upconversion Radio
This paper presents a monolithically integrated IF amplifier and envelope detector for an AM upconversion car-radio receiver. This receiver is intended for the reception of the long-wave and medium-wave frequency bands and uses an intermediate frequency of 10.7 MHz. Specific requirements resulting from the upconversion concept will be illustrated and the basic considerations for maximization of the signal-to-noise ratio as a function of the input signal level will be given. Furthermore, a new method will be presented for fixing the signal levels and the AGC speed in the amplifier. The amplifier uses two emitter-driven variable-gain pairs alternated by negative-feedback current amplifiers. It has an AGC range of 90 dB and a gain of 66 dB. The audio output level is constant within 0.2 dB over the full controll range. A cross-quad compensated envelope detector is driven at a level as low as 30 mV and shows less than 3-percent distortion at a modulation depth of 80 percent.
An integrated wide-band variable-gain amplifier with maximum dynamic range
The design of an integrated wide-band variable-gain amplifier with maximum dynamic range is approached by considering three basic bipolar transistor configurations from which all others can be derived. The analysis of noise and of distortion shows the importance of transistor base resistance in all three circuits. On the basis of these analyses, one configuration is shown to yield maximum dynamic range, and this configuration is then used as the basis for the development of a new circuit called the improved automatic-gain control (agc) amplifier. A unique biasing scheme allows a considerable reduction in distortion and noise, together with a significant increase in bandwidth compared with conventional circuits.
Characterization and measurement of the base and emitter resistances of bipolar transistors
Most previously published methods of measuring transistor base resistance are surveyed and compared. The input impedance circle diagram method is examined in detail and correction factors due to parasitic capacitances are derived. Emitter series resistance is also estimated from this data. A new method of measuring base resistance requiring much less measurement effort is introduced and shown to give good agreement with the circle diagram method. This method is called the phase cancellation method and gives an estimate of base resistance from the common base input impedance at the collector current where its imaginary part is zero. Also an estimate of series emitter resistance is obtained from this measurement and shown to agree well with other methods.