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Signal acquisition circuit

Discussion in 'General Electronics Discussion' started by Muna Hamdan, Apr 22, 2016.

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  1. Muna Hamdan

    Muna Hamdan

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    Apr 22, 2016
    Hello, Im working on a design for signal acquisition circuit, the simulation works fine, but when i built the circuit, it seems that it's highly affected by any movements neraby, the output doesnt show up on the oscilliscope, but when i take a cetain position or move my hand over it, it does! then disappears as soon as i move again. -when it does show up, im sure it's my signal, because i can contol its frequency and amplitude from the function generator. my question is how to stabilize the output?

    Im using instrumentation amplifier in the pre-amplification stage, then another op-amp for band-pass filtering, then a third op-amp for the main amplification, and the problem seems to be in the last stage cuz i can detect the signal fine at the previous ones.
     
  2. dorke

    dorke

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    Jun 20, 2015
    Welcome to EP.
    Can you please post a full diagram of the circuit.
     
  3. Muna Hamdan

    Muna Hamdan

    2
    0
    Apr 22, 2016
    here it is
     

    Attached Files:

  4. dorke

    dorke

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    Jun 20, 2015
    1. What frequencies do you expect to pass through capacitor C3?

    2. What about biasing U3A as you did with U2A ?
     
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