E7H03

What is a phase-locked loop?

1. AAn electronic servo loop consisting of a ratio detector, reactance modulator, and voltage-controlled oscillator
2. BAn electronic circuit also known as a monostable multivibrator
3. CAn electronic servo loop consisting of a phase detector, a low-pass filter, a voltage-controlled oscillator, and a stable reference oscillator
4. DAn electronic circuit consisting of a precision push-pull amplifier with a differential phase input

Pick an answer to check it.