need explanation ?

Discussion in 'General Electronics Chat' started by eng_alaakaa, Oct 7, 2011.

  1. eng_alaakaa

    Thread Starter New Member

    Sep 21, 2011
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    for this design of envelope detector ,
    1- what's the function of D2.
    2- why the output signal is inverted.
    see attached pic.
     
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  2. tgotwalt1158

    Member

    Feb 28, 2011
    111
    18
    The D2 is used as positive peak clamper and hence the out put appears as inverted that is with positive peak clamped to zero volt.
     
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  3. Wendy

    Moderator

    Mar 24, 2008
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    The direction of the diodes will determine which way the peak voltage goes.

    When designing a demodulator like this, be sure the capacitors don't short the audio but do short the RF. It is a common mistake.
     
  4. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    No, the negative peak is clamped to (one diode drop below) zero volts.
    The circuit is a voltage doubler (see Fig. 2).
     
  5. SgtWookie

    Expert

    Jul 17, 2007
    22,182
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    They really should have used a small Schottky diode, like a BAT54. The BAT54's Vf is far lower than 1N4148/1N914 switching diodes.
     
  6. tgotwalt1158

    Member

    Feb 28, 2011
    111
    18
    Yeah Ron I first thought the same that -ve peak is clamped coz of diode's polarity but eng_alaakaa's scope's output is not conforming to that. Could you plz. explain?
     
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