Supply voltages to N and P type semiconductors

[SMOF]

Ok, maybe someone can point me in the right direction ...hopefully anyway.

I know this is probably a really stupid question, but as Mr Mackey in South Park said - "there are no stupid questions, just stupid people", so here it is.

I was in class simulating N and P type CMOS devices using OrCAD. When I had the N type going, we supplied a positive voltage to it (0->5V sweep) and for the P type, we connected a negative voltage (0 -> -5V).

So, simply, why is it a positive voltage for N type, and a negative voltage for P type.

A basic question I am sure, but one I don't fully understand.

Thanks in advance.

Oh, sorry if this is explained somewhere ...I took a qucik look through the Transistor sticky at the top, but some of the links wouldn't open on this PCs

Thanks again.

Seán

 

[es1]

This can be a super in-depth question if one really wants to get into it. But this is a pretty good layman's answer:

http://answers.yahoo.com/question/index?qid=20080222020750AAXLSAn

So in lay-man terms...

N-type semiconductor materials have been doped with elements which have spare electrons in their outer shells. This gives N-type silicon free electrons (which are negatively charged particles) which can move about at will - with the potential to create current.

P-type semiconductor materials have been doped in the opposite way, with elements that have too few electrons in their outer shells. Therefore the opposite of electrons - holes - are free to move about within the material - with the potential to create current.

You can think of it like positive and negative poles of a magnet.

 

[SMOF]

Actually, that's spot on!

Cheers.

Seán