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Optocoupler turn ON

  1. May 31, 2012 #1
    When exactly does a opto coupler turn on, if the emitter voltage is varied.
    See attached.
    Input voltage for the opto is 5V. Drop across the opto is 1v. Total current flowing is 4mA
    The Vcc on transistor side is 12v.
    What should the emitter voltage be, so that the transistor turns on.

    Attached Files:

  2. jcsd
  3. Jun 1, 2012 #2


    User Avatar

    Staff: Mentor

    I'd say it can turn on when VCE>0.2V
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