Which of the following circuits demodulates FM signals?

The discriminator is a circuit specifically designed to demodulate frequency modulation (FM) signals. It takes the modulated signal and translates the frequency variations back into variations in amplitude, which can then be retrieved as the original audio or data signal.

When an FM signal is received, it has frequency variations that correspond to the information being transmitted. The discriminator detects these frequency changes and produces an output that reflects the instantaneous amplitude of the original modulation. This makes it ideal for demodulating FM signals, allowing for the accurate retrieval of the original audio or data content.

Other circuits mentioned, such as the limiter, product detector, and phase inverter, serve different functions. A limiter is primarily used to restrict signal levels to prevent distortion, while a product detector is more typically associated with demodulating amplitude modulation (AM) signals. A phase inverter is mainly used in audio applications to invert the phase of a signal and does not directly demodulate FM signals. Thus, the discriminator is the correct and most relevant circuit for FM demodulation.