I have to project an AM demodulator using an Envelope Demodulator. To which kinds of AM (DSB, DSB-SC, VSB, SSD) is it applicable to?
Thanks
Electrical – AM Demodulation with Envelope Detector
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What you call envelope detector, consists of the detection diode and a low-pass filter. This is one way of demodulating an AM signal, more precisely, it is called asynchronous demodulation.
If you do not connect the diode, and only you process the AM signal with a low pass filter, you get the modulating signal, to which is added the carrier signal. Watch the third oscillogram well. It is the component of the modulating signal to the signal shaping, while is added a proportion of the carrier signal, attenuated by the filter.
The correct operation, is to use the envelope detector. The problem we are having is that the modulating signal is too high (amplitude), so when you make the detection and filtering, unwanted components appear, causing the distortion you see in the second oscillogram.
In the first oscillogram, one can see that the modulation index is extremely high; you should decrease the amplitude of the modulating signal and use the envelope detector to demodulate the transmission.
Often a small DC bias can help improve detection efficiency. Something around 100mV for a germanium diode. Often the DC bias is shared with the transistor bias such as in this design.
A germanium diode actually starts conducting at much less than 300mV 
so it can detect RF of only a few millivolts.
I'm also wondering about the effects of loading on my demodulator, since I will be connecting a voltage amplifier stage before it. Thank you!
Don't you mean after it, not before?
Yes you do have to be careful about loading the demodulator with the following stages. It should have a high input impedance relative to the RC filter after the diode.
What type of receiver are you designing? A TRF(Tuned Radio Frequency) or Superhet (Supersonic Heterodyne)?
Best Answer
Without trying to over complicate things, an envelope detector is generally thought of as only applying to DSB and only when the modulation depth is less than 100%.
Basically if the shape of the modulating signal can be fully seen in the envelope of the modulated carrier, an envelope detector will be the simplest choice.
Hopefully the picture above gives you the idea.
If the carrier is "over" modulated then the envelope of the modulated carrier no longer represents the modulating signal and this certainly applies to DSBSC and any type of single side band modulation.