Abstract: Between the higher-potential power supply and the lower-potential power supply, a pair of first conductivity type MOS transistors having same configurations except for mutually different work functions of the gate electrode and another pair of second conductivity type MOS transistors having the same properties are provided to constitute a differential amplifier. The drain of the other MOS transistor having the second conductivity type is connected to the output terminal and, at the same time, is connected to the higher-potential power supply via a resistor circuit, thereby connecting the gate of one of the above-mentioned pairs of MOS transistors with the first conductivity type to the intermediate point of the resistor circuit. With this, the differential amplifier outputs at its output terminal a voltage corresponding to a difference in gate work function of the pair of MOS transistors having the first conductivity type.