US Patent 7564320 Voltage-controlled oscillator

A voltage-controlled oscillator (VCO) includes: an oscillation unit, for generating an oscillation signal according to a biasing current; a current mirror, for providing the biasing current, the current mirror comprising: at least one first transistor, coupled between a first voltage level and a current source; at least one second transistor, coupled to the first voltage level, a gate of the second transistor is coupled to a gate of the first transistor and the current source; a switch module, coupled to the current mirror; and a control module, coupled to the switch module, for controlling the switch module to adjust the biasing current.