Real transistor operation

I am just a person beginning in electronics on my own . I have been reading how transistors work. All explanations seem to talk about hole flow. But holes don’t really move. Can anyone explain what really happens in an NPN and a PNP transistor? I am thinking that there are two levels of electrons moving. Those that are free in the conduction band and hole movement really being electing movement in the valence band. If someone could explain both but especially PNPs that would be so great. Diagrams much appreciated.

by Kriskan
January 05, 2019
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Answer by mikerogerswsm

If you imagine a bus queue where the first person is offered a lift, he goes away and number two moves up and becomes number one, leaving place number two empty. Then number three moves up to place number two, leaving place number three empty. And so on up the line. The empty place moves in the direction opposite to the direction of the queue. So a hole has moved backward. That is hole flow, and that is the way I explained it to my students, except that I did provide them with visual aids. Any small objects such as marbles or conkers will suffice. It is what everyone accepts. It works.

Now you want to introduce a new theory of your own. I wish you luck and hope it works for you in practice.

Actually physicists may want to understand how PNPs and NPNs transist, but it matters not at all to us electronics guys who make mental models without such theories, in fact we regard current as flowing from positive to negative, whereas actually electron flow is from negative to positive. But then, the whole world is upside down with a south pole in the north and a north pole in the south. Most of physics is inverted, but we just ignore physicists and get on with the realities of good solid engineering.

It's all in the mind you know. (Wallace Greenslade)

+1 vote
by mikerogerswsm
January 05, 2019
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