Coarse tuning bank switch and temperature compensation circuit in low phase noise VCO

摘要

The LC tank of a VCO includes a main varactor circuit and temperature compensation varactor circuit coupled in parallel with the main varactor circuit. The main varactor is used for fine tuning. The temperature compensation varactor circuit has a capacitance-voltage characteristic that differs from a capacitance-voltage characteristic of the main varactor circuit such that the effects of common mode noise across the two varactor circuits are minimized. The LC tank also has a plurality of switchable capacitor circuits provided for coarse tuning. To prevent breakdown of the main thin oxide switch in each of the switchable capacitor circuits, each switchable capacitor circuit has a capacitive voltage divider circuit that reduces the voltage across the main thin oxide switch when the main switch is off.