Can somebody explain phase locked loop PLL and voltage control oscillator VCO in detail?

Question

Circuit with explanation will be appreciated. Thanks

Answer 1

I can't draw circuits here.  What details do you want?

A voltage controlled oscillator is just that- the frequency is determined by the voltage you feed it. Changes in voltage cause a frequency drift, so you want a DC or very low frequency on the input.

A PLL compare the phase of 2 signals.  If they aren't on the same frequency, the output will vary a lot. Typically, the signals are converted to square waves, then drive an exclusive-OR gate.  The width of the output pulse varies, as the time between the leading edges of the 2 signals change.

The 3rd step is to amplify AND FILTER the PLL signal, before applying it back to the VCO. This becomes an error correcting feedback signal.

When the system settles, the VCO is at the same frequency as the reference signal- but with a small phase difference. The PLL will detect that, and output a pulse train. When filtered, this creates a DC signal at Just The Right Voltage to keep the VCO stable.