Patent ID: 7965142

Claim:
A gain control circuit, connected to an amplifier circuit, that is used to output an output signal, comprising: a counter, used to output a counter value continuously; a ramp wave signal generator, connected to said counter, and outputs a ramp wave signal according to said counter value; a processor, connected to said amplifier circuit and said counter, and is used to receive said ramp wave signal and a control voltage signal, and at a voltage of said control voltage signal intersecting said ramp wave signal, obtain from said counter a counter value corresponding to said ramp wave signal as a first counter value and store it temporarily, thus determining a voltage gain of said amplifier circuit by utilizing said first counter value; a voltage detector, used to preset a detection voltage upper limit and a detection voltage lower limit and receive said output signal, and output a detection signal, when a high voltage of said output signal is greater than said detection voltage upper limit, or a low voltage of said output signal is less than said detection voltage lower limit; and a direct current level regulator, connected to said ramp wave signal generator and said voltage detector, and is used to receive said detection signal and adjust a DC voltage level of said ramp wave signal, such that said processor obtains from said counter said counter value corresponding to said ramp wave signal and less than said first counter value, and that serves as a second counter value to update said first counter value, thereby reducing said voltage gain of said amplifier circuit by utilizing said second counter value.