PURPOSE: To keep the fluctuation of frequency caused by the variance of power voltage within a rated range and to omit the elements like a Zener diode, etc., by correcting the junction capacity of an oscillation transistor to a prescribed level despite the variance of the junction capacity.

CONSTITUTION: When a capacitor C1 is connected between the base and the emitter of an npn transistor TR Q10, the pads A-D are provided to a substrate pattern to show the attaching position of the C1. Then a circuit constant is selectively connected to the positions of the pads A-D in accordance with the base-emitter junction capacity Cbe of the TR Q10. Thus the corrected capacity is secured in response to the length of the pattern formed between the TR Q10 and the capacitor C1. Then the variance of frequency can be kept within a prescribed range despite the variance of the junction capacity.