An output amplifier includes an amplifier circuit, a driving stage circuit, an output stage circuit, a first unity gain buffer, and a second unity gain buffer. The amplifier circuit provides an inverted signal and a non-inverted signal, in which the amplifier circuit amplifies an input pixel signal to generate the inverted signal and the non-inverted signal. The output stage circuit passes a supply voltage or a ground voltage to the pixel circuit according to the inverted signal and the non-inverted signal. The driving stage circuit passes the supply voltage or the ground voltage to the pixel circuit. The first unity gain buffer enhances and passes the inverted signal from the amplifier circuit to the driving stage circuit. The second unity gain buffer passes and enhances the non-inverted signal from the amplifier circuit to the driving stage circuit.