Patent ID: 7233200

Claim:
An AGC circuit for varying gain according to a signal level of an input signal and correcting the signal level of the input signal, the AGC circuit comprising: signal level detector configured to detect the signal level of the input signal in units of a period of the input signal and outputting a result of the signal level detection; and gain varying circuit configured to variably control the gain for each period, based on the result of signal level detection, each period corresponding to the result of signal level detection; wherein the gain varying circuit: gradually restores gain at a recovery time constant to a gain corresponding to the result of signal level detection in response to a decrease of the signal level of the input signal, after decreasing the gain in response to a rise of the signal level of the input signal; and switches the recovery time constant based on the result of signal level detection, wherein the result of signal level detection is based on an average shift value of the signal level of the input signal.