PURPOSE: To expand the variable range in the oscillating frequency by providing a means controlling the oscillation intensity of an oscillation circuit in response to a control input used to control the oscillating frequency to the oscillation circuit so as to prevent the oscillation stop when the control input is too high.

CONSTITUTION: An oscillation circuit 10 consists of a couple of transistors(TRs) 12, 13 of differential connection and a current source TR 14 connecting to a common emitter of a couple of the TRs 12, 13, and a means to change the oscillation intensity controls a current flowing to the current source TR 14. Moreover, a reactance circuit 11 is provided with a current mirror circuit whose output current varies with a control input and the means changing the oscillation intensity includes an input TR and a TR of current mirror connection being components of a current mirror circuit. Since the oscillation intensity of the oscillation circuit 10 is increased in response to the control input when the impedance of a positive negative reactance circuit 11 is reduced, the oscillation stop is prevented even when a control variable is increased.