[sdiy] Best & fastest envelope follower schematic.. anybody ?

Martin Klang mars at pingdynasty.com
Thu Dec 16 17:26:16 CET 2021

I think an envelope follower with no lag is called a rectifier.

Jokes aside, there are a number of options available but ultimately it 
comes down to filtering.

For digital envelope followers, I like to use a simple exponential 
average (aka leaky integrator, a first-order IIR filter) on the fully 
rectified signal and tune the time constant to the expected input 
signal. Generally you want it to be fast, but not so fast as to track 
the waveform oscillations, even at say 20 Hz. This makes a 
computationally very efficient follower with predictable results.



On 16/12/2021 01:36, Jean-Pierre Desrochers wrote:
> Here is my goal..
> I need a circuit that will take an AC signal and will shift level it from
> a DC offset extracted from its min & max Peaks..
> Ex: Suppose you have steady +/- 5v peak sine wave coming in this circuit,
> The output would be the same waveform but shifted up to +5vdc.
> So 0 to +10vdc.
> That final waveform would be much usable for a 0-5vdc control voltage 
> input
> than the original AC waveform.
> Now the challenge is to do the same with a level changing AC signal.
> In the case of a _steady waveform_ this ‘level shifter’ could be an 
> opamp that would add half of the peak to peak voltage as an offset DC 
> voltage,
> But here I’m looking for something that will be more versatile
> to handle varying level waveform.
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