Patent ID: 8044729

Claim:
A voltage controlled oscillator (VCO), comprising: a ring oscillator circuit, for providing an output clock signal; and a control circuit, coupled to the ring oscillator circuit, for receiving an output voltage to respectively provide a first voltage-frequency gain and a second voltage-frequency gain so as to control a frequency of the output clock signal provided by the ring oscillator circuit, wherein the first voltage-frequency gain is larger than the second voltage-frequency gain, wherein the control circuit comprises: a filtering circuit, coupled to the ring oscillator circuit, for receiving the output voltage so as to provide the first voltage-frequency gain; and a dynamic loop frequency adjusting circuit, respectively coupled to the ring oscillator circuit and the filtering circuit, for providing the second voltage-frequency gain, and the dynamic loop frequency adjusting circuit comprises: a processing circuit, coupled to the filtering circuit, for outputting a dynamic loop operating voltage; and a capacitive adjusting circuit, respectively coupled to the processing circuit and the ring oscillator circuit, for receiving the dynamic loop operating voltage so as to change a capacitance thereof accordingly.