Patent ID: 8111102

Claim:
An auto gain controller comprising: a variable gain amplification unit configured to receive differential input signals, adjust an amplification gain based on an auto gain control voltage and output differential output signals amplified based on the adjusted amplification gain; and an auto gain adjusting circuit configured to detect at least one peak value of the differential output signals, compare the at least one detected peak value with a reference voltage, generate a comparison signal based on the at least one detected peak value and the reference voltage, and adjust the auto gain control voltage based on the comparison signal, the auto gain adjusting circuit including, a voltage adjusting circuit configured to adjust the auto gain control voltage and the reference voltage based on the comparison signal, the voltage adjusting circuit including, a first selection circuit configured to receive a plurality of control voltages and output one of the plurality of control voltages as the auto gain control voltage based on the comparison signal, and a second selection circuit configured to receive a plurality of reference voltages and output one of the plurality of reference voltages as the reference voltage based on the comparison signal.