| 摘要 |
A phase-locked loop circuit includes a phase comparator that compares phases between a reference signal and a feedback signal and outputs a phase difference signal indicating a phase difference therebetween; a charge pump that outputs a charge pump current according to the phase difference signal; a low-pass filter that includes a resistor and a capacitor and that smoothes the charge pump current and converts the smoothed current into a control voltage; a voltage-controlled oscillator that generates an oscillation signal with a frequency according to the control voltage; and a frequency divider that generates a frequency-divided signal by frequency-dividing the oscillation signal and outputs the frequency-divided signal to the phase comparator as the feedback signal, wherein the resistor in the low-pass filter is a variable resistor that is changed according to the control voltage.
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