Patent ID: 8378721

Claim:
A phase-locked loop circuit comprising: a gm-C voltage-controlled oscillator configured to oscillate at a frequency that corresponds to an input control voltage; a divider configured to divide the frequency of an oscillation signal output from the voltage-controlled oscillator; a phase difference signal generating unit configured to generate a phase difference signal that corresponds to a phase difference between the oscillation signal thus subjected to frequency division by the divider and a reference oscillation signal; a loop filter configured to perform filtering of the phase difference signal so as to generate the control voltage; and a startup circuit configured to inject a seed pulse into the voltage-controlled oscillator based upon the level of a detection signal that corresponds to the control voltage, wherein the gm-C voltage-controlled oscillator comprises: first amplifier having a characteristic of a transconductance; a second amplifier structured to be connected to output terminals of the first amplifier and to have the same characteristic of transconductance as the first amplifier; and a gyrator connected to the second amplifier and capacitors.