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Confusing yet simple looking problem - DC analysis of diode & xstr

  1. Jun 26, 2014 #1
    1. The problem statement, all variables and given/known data
    DC analysis is required for the question in attachment.
    Vz=6V
    B=100
    Vbe=0.7V


    2. Relevant equations



    3. The attempt at a solution
    I tried to find the result using the currents that were defined by the transistor. I found a result that was nonsense, the base current Ib was negative, which is impossible.
    Given in the attachment too.

    Note: I have an exam tomorrow people. Would be awesome if you have guided me. Thanks :))
     

    Attached Files:

  2. jcsd
  3. Jun 26, 2014 #2

    mfb

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    2016 Award

    Staff: Mentor

    It is impossible to tell what you did wrong if you do not show your work...
     
  4. Jun 26, 2014 #3

    rude man

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    Homework Helper
    Gold Member

    Don't use an equivalent circuit for dc analysis. Equiv. ckts. are for small variations about the bias point. Your job is to find the bias point.

    Hints:
    what must be the emitter voltage if the zener is on?
    so then what must be the emitter current?
    so then what is the collector voltage?
    was your assumption that the zener is on, valid? why?
     
  5. Jun 28, 2014 #4
    See where you have placed the 0.7 V voltage drop. Shouldn't it be in 2kilo-ohm resistor branch? Shouldn't there be a short where you have placed the 0.7 volt drop in the above diagram? See this and you can solve.
     
    Last edited: Jun 28, 2014
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