PURPOSE: To lessen the power loss of the amplifier circuit by providing the AC stable power source which is controlled by the output signal or the signal in which the negative feedback signal is piled on the DC signal and then driving the power amplifier circuit with the output of the power source.

CONSTITUTION: The voltage conversion is given to the AC power source via transformer 2, and the AC power source is converted into the plus and minus DC voltage via rectifier circuit 101. Then power amplifier circuit 102 is driven via AC stable power circuit 103. Reference voltage supply terminals 12a and 12b of circuit 103 receive supply of the output signal of circuit 102 or the signal in which the negative feedback signal is piled on the DC voltage, and thus the output of circuit 102 is controlled. The fluctuation of the power voltage and the dispersion of the winding ratio of transformer 2 are absorbed by circuit 103 to supply the fixed voltage to circuit 102 at all times. As a result, the power loss can be reduced at circuit 102, which results in reduction of the thermal feedback from the final-step power part of the power amplifier circuit to the first-step amplification part. Thus a power amplifying IC is obtained with a high fidelity of the signal amplification.