The auto gain-control circuit of photocoupler

Published:2011/5/21 20:25:00 Author:Borg | Keyword: auto gain-control, photocoupler | From:SeekIC

This is a auto gain control circuit of photocoupler, which is mainly consists of AC amplifiers and rectifier circuits. Suppose that we put a AC signal on the non-inverting input terminal of AI, if the input signal is lower than the set value, after it was output by A1 and rectified by A2, the current which go across the LED of MCD521 is minor, so the resistance of the light dependent resistor (LDR) in MCD521 is higher than R1. Therefore, the maximum of total resistance is 30OkΩ(the resistance of RI), and the gain of AI becomes the largest.



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