The function of a tuning circuit to select the desired signal out of the many available, to reject all undesired signal and to increase the voltage of the desired signal are called

Key Points

Selectivity

• Selectivity is defined as its ability to accept or select the desired band of frequency and reject all other unwanted frequencies which can be interfering signals.
• The signal bandwidth should be narrow for better selectivity.

Sensitivity

• The sensitivity of a receiver is its ability to identify and amplify weak signals at the receiver output.
• It is often defined in terms of voltage that must be applied to the input terminals of the receiver to produce a standard output power which is measured at the output terminals.
• The sensitivity of the receiver mostly depends on the gain of IF amplifier. It can be improved by reducing the noise level and bandwidth of the receiver.

Fidelity

• The Fidelity of a receiver is its ability to reproduce the exact replica of the transmitted signals at the receiver output.
• For better fidelity, the amplifier must pass high-bandwidth signals to amplify the frequencies of the outermost sidebands, while for better selectivity the signal should have narrow bandwidth. Thus a trade-off is made between selectivity and fidelity.