Fidelity in a communication receiver is provided by

Fidelity in communications refers to the ability of the receiver to produce an exact replica of transmitted signal. It is provided at output stage of receiver i.e. audio stage.
Fidelity of a receiver is its ability to reproduce the exact replica of the transmitted signals at the receiver output.
In other words, the fidelity of a receiver is its ability to accurately reproduce, in its output, the signal that appears at its input. 
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.
Low frequency response of IF amplifier determines fidelity at the lower modulating frequencies while high frequency response of the IF amplifier determines fidelity at the higher modulating frequencies.