A differential amplifier circuit 110 composed of an inverter is connected to the power supply voltage VCC and the ground voltage GND through a NMOS transistor 142 and a PMOS transistor 144 respectively. The NMOS transistor 142 is connected to the control signal terminal PS, and the PMOS transistor 144 is connected to control signal terminal PS through an inverter 150. The NMOS transistor 142 and the PMOS transistor 144 are controlled such that they can be simultaneously cut off by a control signal from the control signal terminal PS. In this way, the power consumption of the amplifier is reduced.