precision rectifier

Discussion in 'General Electronics Chat' started by anushalalitha, Oct 23, 2008.

  1. anushalalitha

    Thread Starter New Member

    Oct 23, 2008
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    why does a precision full wave rectifier give unequal amplitudes for different half-cycles? How to eliminate this problem?
     
  2. hgmjr

    Moderator

    Jan 28, 2005
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    Do you have a particular precision rectifier circuit in mind?

    Can you attach it?

    hgmjr
     
  3. kubeek

    AAC Fanatic!

    Sep 20, 2005
    4,670
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    Probably because it is autumn, and because birds fly generaly east.

    Would you care to post some schematic or are we supposed to guess??
     
  4. beenthere

    Retired Moderator

    Apr 20, 2004
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    The signal may simply be offset by some DC bias, or have unequal excursions.
     
  5. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
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    Maybe your feedback resistors are mismatched. Maybe your diodes are mismatched. Maybe the universe sneezed. Maybe you should post a schematic.
     
  6. scubasteve_911

    Senior Member

    Dec 27, 2007
    1,202
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    Typically, the full-wave rectifier is composed of two stages. One is a summer, the other is a half-wave rectifier. You are summing the original signal with the rectified version. If these resistors are not matched, then you run into trouble. Use a potentiometer, this will allow you to adjust it with the oscilloscope.

    Steve
     
  7. scubasteve_911

    Senior Member

    Dec 27, 2007
    1,202
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    This is the circuit that I was referring to.

    R3 R4 R5 must be precision resistors!
     
  8. Audioguru

    New Member

    Dec 20, 2007
    9,411
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    The half-cycle amplitudes will be unequal at frequencies higher than about 1kHz if you use lousy old 741 or LM358 opamps. A TL072 dual opamp works pretty well up to 10kHz or 20kHz in that circuit.
     
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