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by marcosdumay 732 days ago
> https://en.wikipedia.org/wiki/Transistor IIRC they are also not symetric

They kinda are. Solid state conductors have those virtual particles called holes, that represent the global state of "having fewer electrons around here". You can have transistors where the electrons are carrying charge or where holes are.

But the properties of holes and electrons are not completely symmetric. Holes disperse each other more strongly.
1 comments
gus_massa 732 days ago
I agree, but think you are talking about the differences of the NPN and PNP transistors, but I'm talking about the differences of the emisor and the collector in the same transistor.

In a very naive explanation, you can exchange the emisor and the collector, but in a real cirtuit it is a bad idea. (I'm not sure why. I think it may stil work but it's slower or less efficient, but I'm not sure about the details.)

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marcosdumay 730 days ago
> I'm not sure why.

On discrete transistors, they have different sizes, shapes and levels of doping.

On the "old" planar VLSI transistors, nobody even uses the names. They are both built as small as possible and there's no space to fine-tune any of their characteristics. But on some of the new 3D VLSI transistors they are different again.

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