PLL

PLL or Phase-locked loop is a control system that generates an output signal whose phase is related to the phase of an input signal. It is an important system used in many communication and electronic devices.

Overview

A phase-locked loop is a feedback control system that automatically adjusts the phase of a locally generated signal to match the phase of an input signal. It is a key component in many types of electronic devices, including radios, computers, and telecommunication systems.

Operation

The operation of a PLL can be divided into three basic steps: comparison, low pass filtering, and voltage control. The PLL compares the phase of the input signal with the phase of the locally generated signal, and generates an error signal that is proportional to the phase difference. This error signal is then filtered by a low pass filter, and used to control the voltage of a voltage-controlled oscillator (VCO). The VCO generates the output signal of the PLL.

Applications

PLLs are used in a wide range of applications. They are used in radio receivers to tune the receiver to the frequency of the incoming signal. They are also used in computers to generate a stable clock signal, and in telecommunication systems to synchronize the operations of different devices.

See also

• Frequency synthesizer
• Voltage-controlled oscillator
• Low pass filter
• Feedback control system

References

PLL Resources
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