PURPOSE: To set a temperature characteristic to a desired value by applying a threshold voltage to a comparator circuit from an emitter follower circuit.

CONSTITUTION: The voltage controlled oscillator is provided with an upperstream measurement current source 10, a lowerstream measurement current source 12, a capacitor 14, a switch 16 and a comparator 18 implementing switch control of the switch 16 to charge/discharge the capacitor 14 for the oscillation. The switch 16 is thrown to the position of a contact (a) or (b) depending on the relation of the quantity of a terminal voltage across the capacitor 14 and comparison threshold voltages VA, VB given to the comparator 18 and the oscillator is oscillated. The threshold voltages VA, VB deciding the oscillating frequency are given to the emitter follower circuit comprising TRs 20, 22, and the temperature characteristic of a VF (base-emitter voltage) of the TRs 20, 22 is changed by the current to adjust the temperature characteristic of the VCO.