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Homework Help: Question about the BJT as switch circuit

  1. Jan 27, 2012 #1
    1. The problem statement, all variables and given/known data
    my teacher wants me to design a circuit to control the on or off of 4 BJTs in the circuit.

    2. Relevant equations

    3. The attempt at a solution
    so i tryed to control a BJT at once .. it workshttp://user.qzone.qq.com/259234914/infocenter#!app=4

    but there were somewrong with control 2 bjt in the circuit .. the BJT can not work whatever i put the value of resistance in the circuit .http://user.qzone.qq.com/259234914/infocenter#!app=4

    Attached Files:

  2. jcsd
  3. Jan 27, 2012 #2


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    Science Advisor

    In the second diagram, the bases appear to be supplied from a negative voltage.
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