PURPOSE: To decrease the power consumption of a power amplifier by providing an HPF to an output side, rectifying an output of the HPF at a rectifier and providing a means to feed back the rectified output to a power.

CONSTITUTION: A fundamental wave and its harmonics are outputted from a power transistor (TR)3 of an output circuit 2 of a power amplifier 1'. A fundamental wave output voltage corresponding to the fundamental wave is fed to a load 6 via an output terminal 7. Further, a harmonic distortion voltage corresponding to the harmonics is rectified by a rectifier 10 via an HPF9, the rectified voltage is converted into a high voltage required for charging a battery 8 by a DC/DC converter 11, and the high voltage charges up the battery. Thus, the power consumption of the power amplifier is reduced by feeding back the harmonic distortion voltage consumed in the power TR to the battery.