envelope follower

[Josh Rowe]

> Date:          Tue, 30 Sep 1997 22:52:14 +0200
> From:          Rene Schmitz <uzs159 at ibm.rhrz.uni-bonn.de>

> To detect the amplitude of the signal u~ =Uo*sin wt
> you need a squaring circuit, that produces Uo^2 sin^2 wt,
> you phase shift the input signal 90  by an integrator( RC=1/w ),
> so that you get Uo * cos wt
> a second squarer gives Uo^2 * cos^2 wt, you sum the both voltages,
> and use a root circuit at whose output you get the Amplitude as a constant
> voltage.
> 
I haven't thought this through completely, but...
The output voltage of an analog integrator is frequency dependant.  
The higher the frequency, the lower the peak-peak output voltage.

So doesn't this mean there is a small snag in the circuit?

( Of course, small snags are what makes designing anything so much of 
a challenge.)

:)

--------------------------------------------------------
Josh Rowe
jrowe at everest.acpl.lib.in.us