Patent ID: 7009472

Claim:
A linear tuning varactor circuit, comprising: a plurality of single-end varactor circuits, each having a tuning terminal and a reference voltage terminal, the single-end varactor circuits coupled in series, a tuning terminal of a first single-end varactor circuit adapted to receive a tuning voltage for tuning a capacitance of the varactor circuit, a reference voltage terminal of a last single-end varactor circuit adapted to receive a reference voltage as a reference level; and a voltage divider, having a first terminal, a plurality of voltage dividing terminals and a second terminal, the first terminal coupled to the tuning terminal of the first single-end varactor circuit, the second terminal coupled to the reference voltage terminal of the last single-end varactor circuit, wherein the voltage dividing terminals of the voltage divider are coupled to nodes of the single-end varactor circuits, and each of the voltage dividing terminals has a divided voltage, which results from dividing a voltage difference between the tuning voltage and the reference voltage by the voltage divider with a pre-set voltage dividing ratio.