Patent ID: 7486152

Claim:
A voltage controlled oscillator comprising: an oscillator circuit configured to generate a predetermined oscillation frequency signal, the oscillator circuit including a resonator element; and an oscillation frequency controller circuit configured to control the oscillation frequency of the oscillator circuit by a control voltage signal, wherein the oscillation frequency controller circuit includes: a first series circuit disposed between one end of the resonator element and a fixed potential, the first series circuit comprising a first varactor diode and a second varactor diode connected in series in this order from the resonator element side for carrying an alternating current, and a second series circuit disposed between an input terminal of the control voltage signal and the fixed potential, the second series circuit comprising a zener diode and a resistor element connected in series in this order from the input terminal side, wherein a terminal of the first varactor diode on the resonator element side and a terminal of the zener diode on the input terminal side are connected for carrying a direct current, and wherein a terminal of the second varactor diode on the first varactor diode side and a terminal of the resistor element on the zener diode side are connected for carrying a direct current.