Patent ID: 7242243

Claim:
A voltage-controlled capacitor circuit having a first output end and a second output end for forming a capacitor between the first output end and the second output end, the voltage-controlled capacitor circuit comprising: a first varactor having two ends, wherein one end is connected to the first output end; the first varactor comprising a metal oxide semiconductor (MOS) transistor, having a source electrode and a drain electrode that are connected to one end of the first varactor, and a gate electrode that is connected to the other end of the first varactor; a first bias voltage being applied to one end of the first varactor and a first control voltage being applied to the other end of the first varactor; a capacitance between the two ends of the first varactor changing according to a difference between the first bias voltage and the first control voltage; and a second varactor having two ends, wherein one end is connected to the second output end; the second varactor comprising a transistor electrically connected between the two ends of the second varactor for forming a PN-junction between the two ends of the second varactor; a second bias voltage being applied to one end of the second varactor and a second control voltage being applied to the other end of the second varactor; a capacitance between the two ends of the second varactor changing according to a difference between the second bias voltage and the second control voltage.