A source driver is configured to drive an organic light-emitting diode (OLED) display panel. The source driver includes a sensing circuit and an operational amplifier. The sensing circuit is configured to sense pixel information of an OLED pixel circuit through a sensing line of the OLED display panel. The operational amplifier includes an amplifier circuit and at least one switch circuit. The amplifier circuit includes at least one gain circuit. An input terminal of the amplifier circuit is coupled to an output terminal of the sensing circuit. Each of the at least one switch circuit is coupled between a pair of output terminals of a corresponding one of the at least one gain circuit.