Automatic input-gain control circuit, and method thereof

An automatic input-gain control circuit and its method in an audio amplifier are provided to minimize distortion of an output waveform caused by clipping of the output waveform by attenuating only a gain of an over-input signal while maintaining an original form of the over-input signal on a specific level or more. An output comparator(510) compares a voltage of an output signal of an audio amplifier with a reference voltage generated based on a threshold voltage. An input gain adjuster(520) automatically adjusts a voltage of an input signal of the audio amplifier according to the comparison result of the output comparator so that the voltage of the output signal is within the reference voltage. The reference voltage is a voltage corresponding to a difference between a power supply voltage and the threshold voltage.