Current flow direction in BJT(Vol. 3)

Discussion in 'Feedback and Suggestions' started by dor, Feb 20, 2009.

  1. dor

    Thread Starter Active Member

    Feb 20, 2009
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    0
    Hi,

    I've read about the BJT in the following page:
    http://www.allaboutcircuits.com/vol_3/chpt_4/1.html

    I think that the electrical current flow direction is inverted.

    It says that in a PNP transistor, the electrical current goes from the base to the emitter ; the same mistake happens with NPN (electrical current goes from emitter to base).

    The same thing occurs in other paragraphs of this chapter.
    That's why I think it's weird - because that there's no chance that the same mistake keeps appearing in your book.
    On the other hand, according to what I've learned, the content in the above quote is incorrect.

    In the NPN BJT, the current goes from base to the emitter.
    In the PNP BJT, the current goes from the emitter to base.

    Thanks,
    Dor.
     
  2. thingmaker3

    Retired Moderator

    May 16, 2005
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  3. KL7AJ

    AAC Fanatic!

    Nov 4, 2008
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    Ahh...you've opened up this ageless, bottomless can of worms. A pox upon thee!

    Actually it's all Ben Franklin's fault. He defined current flow as the flow of IONS in electrolytic solutions. (He didn't call them such, but it's fairly clear from his writings that he UNDERSTOOD what was happening a lot more than we give him credit for). The HOLE flow in seminconductors is the equivalent to ions in liquid form. The ARROW of semiconductors points in the direction of this flow. Except in semiconductors, we don't have liquid ions flowing, we have HOLES, which are simply regions of depleted electrons.

    Now you know. :)

    eric
     
  4. thingmaker3

    Retired Moderator

    May 16, 2005
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    If anyone is interested in debating the merits of one or the other, please use the search function to find an appropriate thread.
     
  5. dor

    Thread Starter Active Member

    Feb 20, 2009
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    Thanks! :)
     
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