PURPOSE: To increase an output voltage higher than a power supply voltage with simple configuration by varying a power supply supplied to a 1st amplifier corresponding to a voltage of an input signal through the processing by a 2nd amplifier.

CONSTITUTION: An output of a 1st amplifier 2 is fed to a 2nd amplifier 4 via a resistor R4, and capacitors C2, C3 repeat charge/discharge of a current supplied through resistors R6, R7 as current supply means in, interlocking with the input signal waveform based on the output limit. Thus, the positive voltage and the negative voltage of the power supply supplied to the amplifier 2 are respectively varied around the voltages +Vcc and -Vcc. Furthermore, the voltage of both the waveform is in interlocking with the waveform of the input signal. Thus, the output signal when the power supply supplied to the amplifier 2 depends on the maximum voltage of both the positive and negative waveforms. Let the maximum voltage be +2Vcc and -2Vcc respectively, the amplitude of the output signal is twice of the amplitude when no power supply control is implemented. Thus, an output with a large level is simply obtained with a low voltage power source.