Patent ID: 8710867

Claim:
An auto-mute control circuit, comprising: an analog amplifier, receiving an input signal and outputting a sensing voltage signal accordingly; a detecting circuit, coupled to the analog amplifier, wherein the detecting circuit compares a common-mode voltage received with the sensing voltage signal received and outputs a comparison signal according to a comparing result; and a direct-current (DC) level adjusting circuit, receiving the comparison signal and accordingly outputting an Up-Down digital signal, a fine tune digital signal and a rough tune digital signal to the analog amplifier to adjust a sensing DC level of the sensing voltage signal, so that the sensing DC level is close to or equal to the common-mode voltage, wherein initial values of the fine tune digital signal and the rough tune digital signal are both “zero”; wherein when the sensing DC level unadjusted is lower than the common-mode voltage, the DC level adjusting circuit sets total bit values of the fine tune digital signal as “one” and outputs the Up-Down digital signal of a high level voltage to the analog amplifier to increase the sensing DC level; when the sensing DC level unadjusted is higher than the common-mode voltage, the DC level adjusting circuit sets the total bit values of the fine tune digital signal as “one” and outputs the Up-Down digital signal of a low level voltage to the analog amplifier to decrease the sensing DC level.