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Hi i am trying to convert positive peak of sine (A.C) signal to D.C (max peak of A.C). I tried in Circuit lab but i am not able to design the circuit fully. 1) I am generating sinewave with 2V. 2) generating square wave with 2.5 as threshold voltage. 3) giving both signal to switch. 4) from the circuit i will get output as only positive cycles of sinewave. negative cycle will be clipped off with the switch. 5) I successfully designed circuit until that. 6) now I want to convert that positive cycle of A.C into D.C. 7) Adding a buffed peak detector will give me always max peak of positive A.C cycle. 8) I have the circuit but I am not able to design in circuit lab. I can't find LM102,LM101 op-amps.

No circuit: no comment.

Please make your circuit public or unlisted.

https://www.circuitlab.com/blog/2012/06/07/unlisted-circuits-easier-sharing-of-schematics/

Also, search CL for:

peak detector

Hi, this is the circuit I have tried but the resistor and capacitor parallel circuit making my positive cycle as zero, I want to eliminate that and i want to use a buffered peak detector. I am providing my circuit url https://www.circuitlab.com/circuit/2ntfcf/demodulator/

Are you trying to make some sort of synchronous detector?

Your output filtering is acting as a pretty agressive low pass filter so you don't see the 125kHz, just the mean DC content.

Move the output2 plot onto a separate Y axis (Advanced Graphing) and you'll see what's happening.

Two suggestions.

i) Remove the filter.

Search CL as suggested then bolt one of those peak detectors onto the output of the switch.

ii) Or, put a cap straight across the output side of the switch, derive a timing signal from the switching signal that is a narrow pulse around the peak of the sinewave so that your switch and the cap function as a sample and hold.

Play time!