Low noise low power charge pump system for phase lock loop

摘要

In a phase lock loop, a charge pump includes a current mirror circuit. The current mirror circuit contains a bias current source and a current mirror source which mirrors the current of the bias current source. The current mirror source is turned on and off in accordance with an output signal from a phase detector to produce correction signals for a VCO. To conserve power, circuits are provided for turning the bias current source on just before it is needed by the current mirror source and for turning the bias current source off just after the current mirror source turns off.