Current flow direction in BJT(Vol. 3)

Thread Starter

dor

Joined Feb 20, 2009
63
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.

The small current that controls the main current goes from base to emitter, or from emitter to base, once again depending on the type of transistor it is (PNP or NPN, respectively).
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.
 

KL7AJ

Joined Nov 4, 2008
2,229
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.

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
 
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