A power amplifier for amplifying a signal includes: an operation amplifier stage, at least one buffer stage and an output stage which are consecutively connected with each other; a first feedback unit connected between an output end of the output stage and a negative input end of the operation amplifier stage; a second feedback unit connected between an input end of the output stage and the negative input end of the operation amplifier stage; a third feedback unit connected between an input end of the at least one buffer stage and the negative input end of the operation amplifier stage; and feedback signals provided by the first feedback unit, the second feedback unit and the third feedback unit being superposed at the negative input end of the operation amplifier stage.