Hearing aid transistor amplifier - has a monolithic integrated circuit differential amplifier with AGC

摘要

The amplifier forward slope is adjustable, and a control voltage, which is a function of the signal voltage behind the amplifier, is applied to its control input. The amplifier has two transistors with positive feed-back and with joined together emitters. A controllable current generator is in the common emitter connection, and a transistor output stage. Collectors of the above two transistors are each connected to an intermediate transistors base. The collector of one intermediate transistor is connected to the base of a first output transistor, and the collector of the other through a phase inverting transistor to the base of a second output transistor of opposite conduction type. Collectors of the two output transistors are joined together, and form the amplifier output.