AGC_SYSTEM_FOR_AUDIO_SIGNALS

Published:2009/6/15 23:32:00 Author:May | From:SeekIC

This circuit is an AGC system for audio-fre-quency signals. AGC systems usually consist of three parts: an amplifier, rectifier, and controlled impedance. In this circuit the functions of an ampltfier and a rectifier are performed by a single op amp. This makes the system simple and cheap.The rectifier is made with the output push-pull cascade of the op amp and RS, RL, and CB. The transistor Q1 and D1 are used as a voltage-controlled resistance (Z). The input signal is (Z + R1)/Z times, diminished by the voltage divider and 1 + R2/R1 times, amplified by the op amp. C2 eliminates influence of dc bias voltage. R3 protects Q1 and D1 from excessive current.



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