From the modulated signal, we can demodulate or detect the modulating or message signal by using a diode and a suitable capacitor filter. The AM signal given to the input of the circuit appears at the output of the diode as a rectified wave. For good demodulation of AM signal the value of RC (which is a time-constant) is chosen such that f1<<RC or RC>>f1
where f is the frequency of the carrier signal.