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  1. #1
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    Analog fast peak detector

    Hi,

    I would like to build analog fast peak detector.
    Signal to measure: PPM - 10ns pulses with 250ns repetition (4MHz), amplitude from 10mV to 5V.
    How circuit I can use to resolve this problem.
    I tested OPA615 but without good results - works witch pulses above 100ns.
    I don't need a very high precision and fast response.

  2. #2
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    Re: Analog fast peak detector

    Hi,

    I tested OPA615 but without good results
    Show your circuit.

    I don't need a very high precision and fast response.
    You want a peak detector for 10ns pulses. 10ns is fast.
    So what do you mean with "no fast response"?

    Klaus
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  3. #3
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    Re: Analog fast peak detector

    I do not need a system that responds quickly to changing a single pulse. The system does not have to be precise. An error of 5% is acceptable to me.
    Click image for larger version. 

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    With 22pF10ns pulse
    Click image for larger version. 

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    With 1nF 10 ns pulse
    Click image for larger version. 

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    Circuit understands amplitude - where is the problem?
    Click image for larger version. 

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    With 1nF and 500ns works.
    Click image for larger version. 

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  4. #4
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    Re: Analog fast peak detector

    Do you mean an analog peak hold detector?
    Zapper
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    Re: Analog fast peak detector

    The 22 pF waveform doesn't make sense, something is apparently not working, wrong diode type, supply voltage range, whatsoever.

    Please give complete information, actual circuit schematic, used parts, probed nodes.



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    Re: Analog fast peak detector

    What is NOT shown in your waveforms is the actual sample/hold signal. It may be that the timing is a few ns off.

    With wide pulses, this may not be a problem. However, 10 ns is fast, and the s/h pulse requires to be timed very precisely, and considering the propagation delays.

    Show the waveforms you including the s/h signal.
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  7. #7
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    Re: Analog fast peak detector

    Quote Originally Posted by schmitt trigger View Post
    What is NOT shown in your waveforms is the actual sample/hold signal. It may be that the timing is a few ns off.

    With wide pulses, this may not be a problem. However, 10 ns is fast, and the s/h pulse requires to be timed very precisely, and considering the propagation delays.

    Show the waveforms you including the s/h signal.
    I'm using OPA615 as a peak detector witch aplication note circuit. I don't use s/h signal. In my circuit pin 7 "HOLD CONTROL" is not connected.



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    Re: Analog fast peak detector

    Why are you using the circuit designed for plus and minus peak signals?
    Zapper
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  9. #9
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    Re: Analog fast peak detector

    Quote Originally Posted by elektrov View Post
    Hi,
    I would like to build analog fast peak detector.
    Signal to measure: PPM - 10ns pulses with 250ns repetition (4MHz), amplitude from 10mV to 5V.
    How circuit I can use to resolve this problem.
    I tested OPA615 but without good results - works witch pulses above 100ns.
    I don't need a very high precision and fast response.
    How about using 2 x LTC6752 in a pulse stretch / one shot circuit as illustrated in datasheet?

    c0x



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