PURPOSE: To stabilize the oscillation operation to the variation in power supply voltage and temperature, by connecting the resonance circuit consisting of capacitor and coil between the input and output of inverter using C-MOSFET.

CONSTITUTION: Diodes D1, D2, D3 and resistor R are connected to C-MOSFET to constitute the inverter 4 and the parallel resonance circuit of coil L and capacitor C and connected between the output and input terminals 5, 6. Further, when the voltage Vcc is fed to the inverter 4, pulse is outputted at the terminal 5, and oscillation is made with the pulse fed back to the terminal 6 via the resonance circuit. In this case, the resonance point is determined for the frequency of the resonance circuit with the condition of phase zero, and the temperature characteristics of capacitor C is compensated with the temperature characteristics of coil L. Accordingly, the oscillated frequency can be stabilized.