Patent ID: 7283006

Claim:
A voltage-controlled oscillator for use with a piezoelectric vibrator, comprising: an amplifier having an inverter and a feedback resistance, the amplifier having a first terminal and a second terminal; and a variable capacitance connected between both terminals of the amplifier, the variable capacitance being configured by a first MOS transistor and a second MOS transistor, wherein gate terminals of the first and second MOS transistors are commonly connected to the first terminal of the amplifier, a source terminal and a drain terminal of the first MOS transistor are short-circuited and connected to the second terminal of the amplifier, and one of a source terminal and a drain terminal of the second MOS transistor is connected to the source and drain terminals of the first MOS transistor, wherein oscillation voltages in opposite phases are to be applied between the source and drain terminals of the first MOS transistor and the gate terminals of the first and second MOS transistors, and oscillation frequency is to be controlled according to a first control signal inputted to the source and drain terminals of the first MOS transistor and a second control signal inputted to the gate terminals of the first and second MOS transistors.