Question
Which of these functions can be performed by a phase-locked loop?
Answer Options
- A) Wide-band AF and RF power amplification
- B) Frequency synthesis and FM demodulation
- C) Photovoltaic conversion and optical coupling
- D) Comparison of two digital input signals and digital pulse counting
Correct Answer: B
Explanation
The Phase-Locked Loop (\text{PLL}) is a highly versatile circuit widely used in modern communications and digital electronics due to its ability to precisely control and track frequencies. Its components (phase detector, filter, \text{VCO}) allow it to perform several critical functions.
The \text{PLL} can perform frequency synthesis (by including a programmable frequency divider in its feedback loop) to generate a stable output frequency that is an exact multiple of the reference frequency. It can also perform \mathbf{FM} demodulation (as the voltage controlling the \text{VCO} is proportional to the input frequency deviation), making it an effective frequency discriminator.
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