Patent ID: 7042297

Claim:
A high frequency oscillator comprising: a first resonant circuit and a second resonant circuit which oscillate at different resonant frequencies from each other; a first amplifying circuit including an NPN transistor, the first amplifying circuit being connected to the first resonant circuit; a second amplifying circuit including an NPN transistor, the second amplifying circuit being connected to the second resonant circuit; a buffer circuit arranged to amplify a signal input from one of the first amplifying circuit and the second amplifying circuit; and a selection circuit arranged to switch operation between the first amplifying circuit and the second amplifying circuit; wherein the selection circuit includes: a first switching circuit including a PNP transistor having a collector terminal connected to a base terminal of the NPN transistor of the first amplifying circuit and an emitter terminal connected to a power supply; a second switching circuit including a PNP transistor having a collector terminal connected to a base terminal of the NPN transistor of the second amplifying circuit and an emitter terminal connected to the power supply; and only one switching control signal input terminal for inputting a control signal; wherein the base terminal of the PNP transistor of the second switching circuit is connected to the switching control signal input terminal and the collector terminal of the PNP transistor of the second switching circuit is connected to the base terminal of the PNP transistor of the first switching circuit.