Could you please tell me whether the phase-locked loop is a phase negative feedback system or a frequency negative feedback system?

ultron001

Could you please tell me whether the phase-locked loop is a phase negative feedback system or a frequency negative feedback system? [Copy link]

I have been struggling with a problem for a long time. Please help me

maychang

“Is a phase-locked loop a phase negative feedback system or a frequency negative feedback system?”

It should be phase negative feedback.

maychang

In the phase-locked loop circuit (whether it is a discrete component or an integrated circuit), there is a phase comparator, which compares the phases of two signals, and its output is proportional to the phase difference between the two signals. Therefore, the phase-locked loop is a phase negative feedback.

maychang

This is the internal block diagram of the phase-locked loop chip 74HC4046A. You can see that there are three phase comparators (PHASE COMPARATOR, in the red box) inside, which compare the phases of the two signals input at pins 3 and 14. The output is fed back to the voltage controlled oscillator (VCO) after passing through R3, R4, and C2.

Of course, only one of the three phase comparators is used, and the other two are idle.

btty038

Phase, negative feedback, consistent amplitude, opposite phase,

gmchen

Phase negative feedback.

The phase-locked loop circuit is a strongly nonlinear system when unlocked. After locking, it can be simplified to a linear system. The input and output variables of this system are both phases, so it is a phase feedback system.

newa11

The phase-locked loop is a phase negative feedback system, which is realized by a phase detector.