BJT Mode

Discussion in 'General Electronics Chat' started by blah2222, Feb 7, 2014.

  1. blah2222

    Thread Starter Well-Known Member

    May 3, 2010
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    36
    Hi,

    Quick question regarding modes of an NPN BJT.

    If current is feeding through the base out through the emitter with zero collector current, is the transistor considered to be in the cutoff region?

    Ic = 0
    Ib = 1mA
    Ie = 1mA

    Thanks!
     
  2. shteii01

    AAC Fanatic!

    Feb 19, 2010
    3,922
    601
    What does the textbook say?
     
  3. #12

    Expert

    Nov 30, 2010
    17,838
    9,172
    That's kind of like, "If the car is rolling downhill, and the transmission is in first gear, but the engine is not running, what mode is that called?" I don't think that is a "mode". Certainly the transmission thinks it is capable of transferring power, but it doesn't have any to transfer. If I had to guess, I'd say it's not in cutoff, but neither is it in the linear region. More like, "What mode is a transistor in if I didn't connect it correctly for any mode?"
     
  4. alfacliff

    Well-Known Member

    Dec 13, 2013
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    if the base to emtter is drawing current, the transistor should be conducting. is there anything connected to the collector preferably positive.
     
  5. blah2222

    Thread Starter Well-Known Member

    May 3, 2010
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    36
    Collector is not connected to anything, hence Ic=0.
     
  6. inwo

    Well-Known Member

    Nov 7, 2013
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    Starvation mode. I've heard it called.

    Not enough collector voltage.
     
  7. tindel

    Well-Known Member

    Sep 16, 2012
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    You have a diode in that mode...
     
  8. crutschow

    Expert

    Mar 14, 2008
    16,206
    4,330
    I agree with tindel. The transistor base-emitter junction is acting as a two-terminal diode. The collector has no effect since it is open.
     
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