The invention relates to a power amplifier which comprises a sum and difference modulation module, a differential delay control module and an output stage module, wherein the sum and difference modulation module integrates and quantizes errors of a differential mode input signal and a differential mode output signal, and generates a first average signal and a second average signal; the differential delay control module comprises a first delay control module and a second delay control module which respectively receive the first average signal and the second average signal, and the first average signal and the second average signal are logically processed to generate a first signal and a second signal corresponding to the first average signal as well as a third signal and a fourth signal corresponding to the second average signal. The differential delay control module respectively decides the delay time between the first signal and the second signal as well as the delay time between thethird signal and the fourth signal according to the first control signal and the second control signal, the output stage module is controlled by the first signal, the second signal, the third signal and the fourth signal to generate the output signal so as to drive a load.