Linear Detector for AM Demodulation
We can simply a rectifier using a linear detector. It’s not only have no gain, but also no distortion. An example from two op-amps is the easy one as shown in the following circuit diagram.
The second op-amp is a precision half-wave rectifier (the second diode is to “catch” the op-amp on the other half-cycle and prevent it from saturating). Take a note that the second op-amp eliminates the diode drop. We can see easily the high frequency ripple in the output, but he output does reproduce the modulating signal. If you have an amplifier and loudspeaker, listen to it as well and you will see what happens for an overmodulated signal.