I'm trying to make sense of current direction in diodes and transistors.
What does it really mean, and how do you folks think about it?
This is really about "conventional" vs "electron" theory I guess.
Does it really even matter?

thanks,
Jay

 

Physically speaking, the ocnvention you use will not matter. However, I strongly recommend you just go with conventional current flow. Since almost all of the literature uses this convention it will just be easier for you to grasp if you follow what everyone else does.

I think about current flow in the conventional sense and that gets me by 99% of the time. There are a few cases where it is useful to think about electron flow:

1) Semiconductor physics! Probably what you're doing right now :-)
2) Photo-electric devices. Things that involve photons releasing electrons and vice-versa.
3) SOme cases in electrostatics, magnetostatics, electromagnetics.
4) Sometimes when working with moving charge around, charge coupled devices, charge integrators etc...

But even in these examples, one can always still use conventional flow. I guess its just what you get used to doing and following trends in textbooks & literature.

 

Engineers use "conventional" electron flow, in which we say the current flows from the Positive side of a power source to the negative side. The arrows on all component schematics, such as diodes, follow Conventional flow because, well, engineers designed and made them. So with a diode, using conventional flow, you say the current flows the same way as the arrow on the diode... makes it really simple.


HOWEVER, current, or electrons, ACTUALLY in real life flow from the negative side of a power source to the positive side. For some reason, this is what they usually teach technitions and hobbists pick up on it. Becuase of this, they have to think backwords, in other words... they have to think the current flows AGAINST the arrow of the diode in a schematic. Even though it's the real way it happens, it can get confusing...

i suggest you use Conventional flow, more textbooks that i've seen use it, and it makes reading schematics alot easier.

 

I think you're confusing the issue further here!.

We were taught 'conventional current flow', which was from positive to negative, and also 'electron flow' from negative to positive.

'Conventional electron flow' doesn't make sense!.

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I prefer to think in terms of "conventional current" which flows from +ve to -ve.
This does for most circuit analysis.
I will sometime switch to "electron flow" (-ve to +ve) when considering circuits using good old valves.

JimB

 

The best thing abt a diode symbol and a BJT symbol is the arrow that is part of the symbol. The way the arrow point denots the way current can only flow (without getting too compleicated with reverse breakdown and all )

 

Bill Beaty has some interesting things to say about electricity in general, and the nature of current flow.
If you've never visited Bill's web site, check it out. It's huge and fun to explore.