CONSTANT VOLTAGE CIRCUIT DEVICE

PROBLEM TO BE SOLVED: To provide a constant voltage circuit device capable of supplying a stable output voltage even when leakage currents are produced in an output transistor, and obtaining a stable off state. SOLUTION: This constant voltage circuit device is provided with an operation amplifier 3 for controlling the output impedance of a Pch-MOS transistor 5 connected between a power source terminal 1 (or ground terminal) and an output terminal 6, and an output voltage value is set by resistances 8, 9, and 10 connected between the output terminal 1 and the ground terminal 15 (or power source terminal). This constant voltage circuit device is also provided with an output voltage abnormality preventing Nch-MOS transistor 12 serially connected to the Pch-MOS transistor 5 and an output voltage detecting operation amplifier 11 for controlling the output impedance. Thus, the output voltage abnormality due to the leakage currents of the Pch-MOS transistor 5 can be detected, and the output voltage abnormality can be compensated.