Extra exam question E7H03
Subelement E7, PRACTICAL CIRCUITS· Group E7H
What is a phase-locked loop?
- A.An electronic servo loop consisting of a ratio detector, reactance modulator, and voltage-controlled oscillator
- B.An electronic circuit also known as a monostable multivibrator
- C.An electronic servo loop consisting of a phase detector, a low-pass filter, a voltage-controlled oscillator, and a stable reference oscillator (correct answer)
- D.An electronic circuit consisting of a precision push-pull amplifier with a differential phase input
WhyA phase-locked loop is an electronic servo loop consisting of a phase detector, a low-pass filter, a voltage-controlled oscillator, and a stable reference oscillator. A phase-locked loop is an electronic servo loop made up of a phase detector, a low-pass filter, a voltage-controlled oscillator, and a stable reference oscillator, continuously comparing the VCO's output phase against the reference and correcting it to keep the two locked together, answer C. It isn't built from a ratio detector and reactance modulator (those are FM-related components used elsewhere), isn't the same thing as a monostable multivibrator, and isn't a push-pull differential-phase amplifier, none of those describes a PLL's actual structure.
Published 2026-08-28 · Last updated 2026-08-28 · Question text is verbatim from the 2024-2028 NCVEC Element 4 pool (public domain); the explanation above is original writing, see our methodology.