Small signal amplifier

Abstract

Abstract 1410133 Transistor amplifying circuits MOTOROLA Ltd 6 July 1973 [12 July 1972] 32325/73 Heading H3T A small-signal amplifier comprises a first transistor 15<1> with its collector earthed and its emitter connected to the base of a second transistor 16<1> of opposite conductivity type, which is in common emitter connection. The transistor 16<1> is coupled to an emitter-follower output stage 20<1>, from the emitter of which current is obtained for the transistor 15<1>, via feedback resistor 25<1>. The resistors are so chosen that the quiescent potential of the output terminal 22<1> is mid-way between that of the supply terminal 18<1> and earth. As shown a microphone 12<1> is coupled to the amplifier via resistors 31<1>, 32<1> and a shunt diode 30<1> which limits positive-going signals, negative-going signals being limited by the base-collector diode formed by transistor 15<1>. In a simplified arrangement (Fig. 1, not shown) a microphone is connected directly to the base of the first transistor.

Inventors

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