Envelope Follower

Unlike the usual envelope detectors using a diode and a lowpass this circuit is combined from a peak hold that is sampled and held after the zero crossing. The CMOS switches discharge the peak hold cap after it has been sampled. The phase errors of lowpass detectors are unknown to this circuit. The applications of this circuit are synthesizers, companders, voice processors and maybe vocoders.

Originally an Elektor circuit I tweaked it to operate on +/-15V. (Originally diode/resistor at N1 ommited, and all ICs +/- 5V operated)