audio frequency AGC amplification circuit

Published:2011/5/5 18:55:00 Author:TaoXi | Keyword: audio frequency, AGC, amplification | From:SeekIC

The audio frequency AGC can track and keep watch over the preamplifier's output audio signal voltage level, when the input signal increases, the AGC circuit automatically reduces the gain of the amplifier; when the output signal reduces, the AGC circuit automatically increases the gain of the amplifier to keep the best level of the signal which is got into the A/D, and also it minimizes the reduction wave. The audio frequency AGC amplification circuit is as shown in the figure, this kind of amplifier's dynamic range is greater than 50dB, the output distortion is very small, and it has some points of advantages such as starts fast, decay slowly. You can adjust the voltage level of the circuit input 40～20mV and output 0～1.2V, it has the single power supplier, and the current consumption is less than 1mA(5V voltage). VT2 and VT4 are the P-channel JEFT, it constitutes the equivalent resistor divider with R2, R3, R4 (R10, R11, R12), also it accesses to the input circuit. When the input voltage level is less than 40mV (peak-peak), the input voltage assigns between R2 and R3,R4 equally. A1's output amplitude is not enough to conduct the positive peak detector VT2.



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