Programable gain amplifier and gain control method

Abstract

A program gain amplifier includes an operational amplifier and a capacitor array. The capacitor array includes a first, second, and third capacitors selectively coupled to the operational amplifier or ground according to a first, second, and third switches, respectively. The first, second, and third capacitors have a first, second, and third capacitance, respectively. The third capacitance equals a sum of the first and second capacitance. In a first configuration, the first and second switches are operated at a first conductive state, and the third switch is operated at a second conductive state. When converting to a second configuration from the first configuration, the third switch is operated at the first conductive state, and the first and second switches are operated at the second conductive state. The gain being provided to an input signal in the first and second configurations are the same.