Fast Envelope Sampler

020 FAST ENVELOPE SAMPLER RADIO & TV When a signal is being amplitude-modulated, constant moni- quency does not exceed half the carrier frequency. The fast enve- toring is necessary to ensure that the maximum modulating fre- lope sampler presented here is basically an advanced AM ELEKTOR ELECTRONICS JULY 1989 SUPPLEMENT A2 7 2 -6> 100P demodulator that can be used with modulations where the well- known diode detector with LF filter can not. Phase errors that occur with diode detection are absent in this circuit. Amplifier IC1 is a buffer with variable (1-11) AC amplification. Opamps Al and A3 form an active half-wave rectifier that charges capacitor C5 up to the maximum signal level in a half period. During the zero crossing, detected by A2, the network around N2 generates a short pulse. This pulse ensures that the potential across C5 is applied to C6 via electronic switch ES4. After ES4 has been opened, so that the charge is stored safely in C6, capacitor C5 discharges via pa...