PURPOSE: To obtain a circuit having an oscillation frequency with less power voltage dependancy by using a positive current, or a negative current or both so as to control the operation current of an inverter thereby stabilizing the operating current of the inverter.

CONSTITUTION: A reference voltage of VCC and N1 generated from the circuit 1 is fed to a gate of a P-channel MOS transistor (TR) Q3 of an inverter section 3 in an oscillation circuit comprising a reference voltage generating circuit 1 and an oscillation section 2, and a TR Q3 is operated at the saturation region when the source potential is high and the source-drain current is constant in dependently of the source potential. Moreover, the potential difference between VCC and N1 of the circuit 1 has a very small voltage dependancy and its poten tial is used as the gate potential thereby decreasing the source-drain current of the TR Q3. Thus, the switching speed of the CMOS inverter of the inverter section 3 is constant because the positive/negative current is unchanged. The switching speed of the CMOS inverter is constant as to inverter sections 4, 5 independently of the power voltage.