what does NPN and PNP sensor stand for??


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does anyone know what these terms stand for actually?? i know the pnp is a sourcing and the npn is a sinking device, but do the letters actually stand for something?? i am working on a research project for school and would appreciate any help. thanks...
NPN = Negative Positive Negative (transistor type) that has a p-type semiconductor base with a n-type semiconductor collector and emitter.
PNP = Positive Negative Positive (transistor type) that has a n-type semiconductor base with a p-type semiconductor collector and emitter.
David Baird
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These are just certain Material depending on what the transistor is. N type and a P type each have a different type of material combined a certain way to control the flow of electrons. I can get really deep on all this and write a page of nonsense on exactly what these are. For example Electrons and Holes in an intrinsic semiconductor, The covalent Bond, Donors and acceptor Impurities...or

It could be n = magnitude of free-electrons (negative) concentration

p= Magnitude of hole (positive) concentration...

Basically PNP and NPN just know that it is either current sinking or current sourcing because if you want to know about the initials you have to get down on a mollecular level... I always remember npn by the transistor is not pointing n.

This prolly didnt help any but there is no easy was of explaining it you just have to read it and know it!
thanks for the explanation. that's better than nothing... at least i know now it is pretty complicated..