Trying make a high frequency peak detector and I have a couple of questions.

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justneedone

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Trying make a high frequency peak detector, i have a couple of question.

hello all,

i am trying to make a peak detector using npn bjts as diodes and lm318 opamp. my input is a sinewave. so far my circuit works for frequency between 10k to 100k but as i start getting to higher frequency there is an voltage overshoot on the cap. i dont understand why there is an voltage overshoot, can somebody provide me with a solution. Note: my circuit has to go to 500KHz and the cap has must be discharging between the negative input wave.



this is at 2.5 V and 100k


this is at 2.5V and 200k
 

Re: Trying make a high frequency peak detector, i have a couple of question.

How did you arrive at the component values, e.g. sampling cap? Not sure if LM318 is fast enough at the end, but quite surely a lower sampling charge time constant is required.
 

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