Choosing capacitance for peak detector

Discussion in 'General Electronics Chat' started by anhnha, Dec 25, 2015.

  1. anhnha

    Thread Starter Active Member

    Apr 19, 2012
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  2. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    the value of the capacitor for the dector depends on the speed versus the accuracy.
    A small capacitor will make it fast, but leakage will let the voltage drop.
    A large capacitor will make it slow, but it will keep the maximum value much longer.

    Bertus
     
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  3. anhnha

    Thread Starter Active Member

    Apr 19, 2012
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    Thanks for the answer!
    I think time constant RC is what relating to speed and accuracy here?
    With RC is small, it will charge and discharge fast.
    Is there a detailed treatment of this? I tried to search but couldn't find a good one.
     
  4. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    A peak detector is used for keeping the maximum value of a signal.
    An envelope detector will follow the changes in signal.
    The following pdf will give you more info on the envelope detector:
    http://educypedia.karadimov.info/library/tut331_04am_dem.pdf
    Page 6 will tell you about the effects of the RC time.

    Bertus
     
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  5. RRITESH KAKKAR

    Senior Member

    Jun 29, 2010
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    Vc=5(1-e^-t/RC)
     
  6. anhnha

    Thread Starter Active Member

    Apr 19, 2012
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    Actually, I am using the structure (peak detector) as a rectifier. So, I think there should be a balance here.
     
  7. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    The simplistic peak detector shown in chapt 3 is missing a crucial element, which is a discharge path for the capacitor. The effect of the discharge path (load) must be factored into the charging time, as well as the discharging time...

    327.gif
     
    Last edited: Dec 25, 2015
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