Modeling op-amp as a differential amplifier

Discussion in 'The Projects Forum' started by Gtofig, Jan 16, 2008.

  1. Gtofig

    Thread Starter Member

    Jan 4, 2008
    14
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    In my project, I used OP-AMP as a differential amplifier with single-ended output.
    The problem is, I can't use op-amp itself. I need to model it with transistors and resistors, without using any IC's or current sources. My idea was to use BJT differential amplifier with current mirror as a current source but I faced a problem. Both differential amplifier and current source work seperately, but when you connect them together, current source is not working. Any suggestions?
     
  2. scubasteve_911

    Senior Member

    Dec 27, 2007
    1,202
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  3. Gtofig

    Thread Starter Member

    Jan 4, 2008
    14
    0
    No, I don't really need the whole op-amp.. Only a differential amplifier.. I know it seems simple, but somehow it doesn't work in MultiSim.. As I told, I used simple BJT differential amplifier. And instead of current source I connected a current mirror to BJT's emitters. And when I did that, current mirror stopped working..
     
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