Transistor design done, just have a problem

Discussion in 'The Projects Forum' started by Tahmod, Mar 2, 2013.

  1. Tahmod

    Thread Starter New Member

    Feb 23, 2013
    12
    0
    I have built this circuit, but the problem is that I dont know how to find the emitter and collector resistor to provide me a 250mA.

    This is found from the circuit by measuring:
    Rc=24ohms

    These are my Start value taken from the datasheet:
    Vce=1.2
    Ic=0.3A
    Ib=1.5mA
    Hfe=200


    KVL load:
    Vcc-vc-Vce-Ve=0
    Vcc-Vce=IcRc+IeRe
    Vcc-Vce=IbBRc+IbBRe
    (Vcc-Vce)/IbB=Rc+Re
    (6-1.2)/(1.5*10^-3 *200)=24 + Re
    16ohms=24ohms+Re
    16-24=Re
    -8=Re


    1.-I got a negative resistance what is wrong with this resistor? :)2..
    2.-Maybe is the data, I took from datasheet is wrong?
     
  2. wayneh

    Expert

    Sep 9, 2010
    12,090
    3,027
    Care to share it with us? I can't imagine how to help without it.

    Be careful using datasheet values - they have very specific meanings and may only apply to very narrow situations.
     
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