Patent ID: 7078980

Claim:
A voltage controlled oscillator comprising: a resonance unit having first and second output terminals, for causing oscillations to output complementary alternating-current signals from said first and second output terminals, said resonance unit comprising: an inductor connected between said first and second output terminals; a first variable capacitor connected in parallel with said inductor; a second variable capacitor having one of its electrodes connected to said first output terminal; a third variable capacitor having one of its electrodes connected to said second output terminal; a first switch for switching the other electrode of said second variable capacitor between floating and being subjected to a third potential; a second switch for switching the other electrode of said second variable capacitor between floating and being subjected to a fourth potential different from said third potential; a third switch for switching the other electrode of said third variable capacitor between floating and being subjected to said third potential; and a fourth switch for switching the other electrode of said third variable capacitor between floating and being subjected to said fourth potential; and an amplifying unit for fixing a high level potential and a low level potential of the signals output from said first and second output terminals to a first potential and a second potential lower than the first potential, respectively, wherein said first and third switches cooperate with each other to switch both the other electrodes of said second and third variable capacitors between floating and being subjected to said third potential, and said second and fourth switches cooperate with each other to switch both the other electrodes of said second and third variable capacitors between floating and being subjected to said fourth potential.