A phase-locked loop (PLL) is a control system that generates an output signal whose phase is related to the phase of an input signal. Here is how a PLL circuit typically operates:
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Phase Detector: The PLL compares the phase of the input signal (reference signal) with the phase of the feedback signal (output signal) using a phase detector. The phase detector generates an error signal that represents the phase difference between the two signals.
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Loop Filter: The error signal is then filtered by a loop filter to remove noise and unwanted signals. The filtered error signal is used to control the voltage-controlled oscillator (VCO) in the next step.
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Voltage-Controlled Oscillator (VCO): The VCO generates an output signal whose frequency is directly proportional to the input voltage it receives. The filtered error signal from the loop filter adjusts the VCO's frequency to minimize the phase difference between the input and output signals.
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Feedback Loop: The output signal from the VCO is fed back to the phase detector, closing the loop. By adjusting the VCO's frequency based on the phase difference, the PLL locks the output signal's phase to the input signal's phase.
Overall, a PLL circuit operates by continuously adjusting the VCO's frequency to maintain phase synchronization between the input and output signals.
