Patent ID: 6246285
Filing Date: 2001-06-12
Classification: H03G

Abstract:
An automatic gain control (AGC) circuit based on a peak detection system comprising:a voltage-controlled amplifier having a gain varying in response to a control voltage and amplifying a modulated signal with the gain;a wave detector detecting the modulated signal amplified by said voltage-controlled amplifier;a first comparator comparing a detection signal output by said wave detector to a comparison voltage and outputting a first comparison signal;a second comparator comparing the detection signal to one of a first voltage and a second voltage, and selecting one of the first voltage and the second voltage based on comparison of the one of the first and second voltage selected to the detection signal and outputting a second comparison signal;a first filter receiving the first comparison signal and outputting an output signal having a voltage which increases or decreases based on the first comparison signal; anda second filter receiving the second comparison signal and selecting a cut-off frequency based on the second comparison signal and supplying the output signal, after low-pass filtering based on the cut-off frequency selected, to said voltage-controlled amplifier as the control voltage.