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Differential Amplifier Doubt

Discussion in 'General Electronics Discussion' started by rdevendrakumar1989, Sep 4, 2012.

  1. rdevendrakumar1989

    rdevendrakumar1989

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    Aug 9, 2012
    Hai friends,

    Am design a circuit to measure resistance value interms of voltage by using differential amplifier... Am use voltage follower for each input.. But differential amplifier output comes only 70%. am also nullify the offset voltage.. Whats the reason for that.. Give me solution as soon as possible pls
     
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    9,137
    1,846
    Nov 17, 2011
    Give us a schematic as soon as possible pls.
     
  3. rdevendrakumar1989

    rdevendrakumar1989

    29
    0
    Aug 9, 2012
    [​IMG]


    v1 and v2 are the 2 ends or resistor
     
  4. Harald Kapp

    Harald Kapp Moderator Moderator

    9,137
    1,846
    Nov 17, 2011
    In principle the circuit should work. What are the voltages (supply, V1, V2, Vout)? What type of OpAmp are you using?
    Are you sure the difference voltage at Vout is within the operational range of the OpAmps?

    Also: The OpAmp has a (admittedly very) small input current.You need to provide a path to ground for this current. See this application note.
     
    Last edited: Sep 5, 2012
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