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BJT circuit infinite gain

  1. May 24, 2014 #1


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    Here is my task:
    Calculate Iout if all BJT's have identical characteristics with β→∞, work on same temperature in forward active mode. Use BJT exponential transfer characteristic.

    Since β→∞, IB for every BJT should be zero amps and IC=IE. Equation for BJT exponential transfer characteristic is Ic=Is*e^(VBE/Vt) but I don't know how to use it in order to find Iout. Any idea? Iout should be I1*I2/I3.
  2. jcsd
  3. May 25, 2014 #2

    rude man

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    Using ic1 = is exp(Vbe1/VT), compute Vbe1. Note ic1 = I1.
    Then using I2, compute Vbe2.
    Etc. until you get to Vbe4. Finally, compute ic4 = Iout.
  4. May 25, 2014 #3


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    Done. Thanks a lot!
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