Patent ID: 7569912

Claim:
A voltage controlled oscillator (VCO) module coupled between a power terminal and a grounding terminal, and having a first terminal and a second terminal, comprising: a frequency tuning circuit containing a differential variable capacitor for receiving a predetermined tuning signal for altering capacitances of the differential variable capacitor, wherein the differential variable capacitor comprising: a semiconductor substrate having a first conductive type; a well region having a second conductive type, disposed on the top surface of said semiconductor substrate; at least three implant regions, including a first implant region, a second implant region and a third implant region each disposed on the top surface of said well region; a voltage control terminal connecting to said first implant region, said second implant region and said third implant region; a first gate coupled to the first terminal and formed on the well region between the first implant region and the second implant region; a second gate coupled to the second terminal and formed on the well region between the second implant region and the third implant region; and a core circuit coupled in parallel with the frequency tuning circuit for providing an oscillation mechanism, wherein the first implant region and the third implant region use the second implant region as a center to be disposed symmetrically on both sides of the second implant region, and the first gate and second gate use the voltage control terminal as a center to be disposed symmetrically on both sides of the voltage control terminal.