BJT Symbols for NPN & PNP Reversed

Thread Starter

Thnker

Joined Jun 30, 2009
1
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).
 

Wendy

Joined Mar 24, 2008
21,839
Try pointing to the book on this site, it is easier to link. If you are talking about this it is correct.



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

The arrow points to the negitive junction.
 
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:

Wendy

Joined Mar 24, 2008
21,839
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.
 

Dave

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

Dave
 
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