Practical transistor problem

Discussion in 'General Electronics Chat' started by TheNight Silence, Apr 3, 2016.

  1. TheNight Silence

    Thread Starter New Member

    Feb 4, 2016
    13
    0
    Pls I've seen this thread and i don't know how they get the answer
    http://forum.allaboutcircuits.com/threads/another-transistor-circuit-problem.89348/

    i think all available equations is 3 eqn,one at the input and two at the output
    at i/p
    Ib=(1-0.7)/120^3=2.5ua
    and at the o/p
    i assumed the transistor in the active region to apply the rule Ic=B*Ib,
    then Ic=80*2.5u=200ua
    1st eq
    20=It*10^3+Vce
    2nd eq
    It : is the total current =Ic+Io
    Vo=Io*10^3
    then how to get the total current since Vce is unknown
     
  2. Papabravo

    Expert

    Feb 24, 2006
    10,135
    1,786
    Vce = Vo for this problem. You write the sum of the currents into and out of the node at Vo equals 0 and it drops out. You have one equation in one unknown. The answer is 9V, not 12 as the problem stated.

    -\left (\frac{20 - v_o}{10\text K}\right )\;+\;200 \text \mu A\math\;+\;\left (\frac{v_o}{10\text K}\right )\; =\; 0
     
    Last edited: Apr 3, 2016
  3. TheNight Silence

    Thread Starter New Member

    Feb 4, 2016
    13
    0
    oh my god,
    it's very simple
    Thanks very much
     
  4. Papabravo

    Expert

    Feb 24, 2006
    10,135
    1,786
    U R welcome
     
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