To provide a simple inexpensive oscillator of an integrated circuit, and its method, which has frequency stability improved over a selected frequency range, by reducing an influence of process changes and temperature changes on a base current of a bipolar transistor of an oscillator of an integrated circuit.

Into a voltage follower circuit which the oscillator of the integrated circuit comprises, a base current to be provided by not a capacitor but a current mirror is made to flow. As a result, electric charges in the capacitor do not change so large as to change the frequency of the oscillator practically, by changes in the base current of the bipolar transistor over an operating temperature range.