BJT Symbols for NPN & PNP Reversed

Discussion in 'Feedback and Suggestions' started by Thnker, Jun 30, 2009.

  1. Thnker

    Thread Starter New Member

    Jun 30, 2009
    1
    0
    In the E-Book (http://openbookproject.net//electricCircuits/Semi/SEMI_4.html), the symbols for NPN and PNP transistors seem to be reversed - at least according to the bjt wiki and at least one textbook.

    Am I missing something? The text describes the arrow on a BJT symbol as being opposite that of the direction of the emitter current. Textbooks and the wiki show the opposite (for an NPN, the arrow points "out" and is the same direction as the emitter current).
     
  2. Wendy

    Moderator

    Mar 24, 2008
    20,764
    2,534
    Try pointing to the book on this site, it is easier to link. If you are talking about this it is correct.

    [​IMG]

    BJT transistor: (a) PNP schematic symbol, (b) physical layout (c) NPN symbol, (d) layout.

    The arrow points to the negitive junction.
     
  3. StayatHomeElectronics

    Well-Known Member

    Sep 25, 2008
    864
    40
    The image just below the one Bill Marsden included shows the direction of electron flow.

    http://openbookproject.net//electricCircuits/Semi/03073.png

    Several quotes from the book:

    "Small electron base current controls large collector electron current flowing against emitter arrow."

    "According to the standards of semiconductor symbology, the arrow always points against the direction of electron flow."

    The direction of current flow and the direction of electron flow are in opposite direction. I think these images show electron flow instead of current flow. The arrows below the diagram should maybe state controlling and controlled electron flow...
     
    Last edited: Jun 30, 2009
  4. RiJoRI

    Well-Known Member

    Aug 15, 2007
    536
    26
    Mnemonic from Tech School:

    NPN = "Not Pointing iN"
    PNP = "Pointing iN"

    --Rich
     
  5. Wendy

    Moderator

    Mar 24, 2008
    20,764
    2,534
    Truth, unless a picture leaps out that is wrong (which I'm not discounting, but feel is unlikely), I think it should stay as is. If it ain't wrong, don't fix it.
     
  6. Dave

    Retired Moderator

    Nov 17, 2003
    6,960
    144
    I concur with the comments, the symbols are correct as presented and no corrections are needed.

    Dave
     
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