# Current flow + to -

When reading circuits, more specifically let's control an npn.

Via conventional flow you can say, when the base sees 0.6v the transistor begins to conduct.

But, if you imagine the flow from negative to positive, how's the transistor switch on? As the flow would be leaving the base pin?

How deep down the rabbit hole do you want to go?

http://jacquesricher.com/NEETS/14179.pdf

if you imagine the flow from negative to positive, how's the transistor switch on?

By injecting electrons into the base region of the transistor.

How do you reconcile PNP transistors?

Sorry, Grumpy_Mike, that question was directed at cjdelphi.

See 2-6 thru 2-14 of the previously mentioned
http://jacquesricher.com/NEETS/14179.pdf

It all comes down to how the NP and PN junctions are "biased" within the transistor to permit current flow, a lot, a little, or not at all.

But, if you imagine the flow from negative to positive, how's the transistor switch on? As the flow would be leaving the base pin?

The simple answer is - The Base-Emitter junction and the Base-Collector junctions both "act like" a diode and current can only flow one direction. With an NPN transistor, current flows from the base to the emitter and from the collector to the emitter. The emitter current is the sum of both currents.

Via conventional flow

If you study the physics of transistors, electrons flow in the opposite direction of conventional current.

And, as was hammered into my contemporaries and myself by an instructor named 'Bill Sparks' (that was inspiring by itself), "Current does not flow, current is flow"...... (do wha? dang it, whats that mean? Is he talking about the arrow head thingie, or the bar thingie? Maybe I shoulda said I wanted to be a mortor man....)

Electrons are negatively charged so, when a potential difference is applied, they 'flow' (jiggle would be more descriptive at quantum level) from negative to positive.

In order to reconcile with conventional current then you consider the elctron holes to be positive and hence conventional current is the flow of positive holes towards a negative potential.

Atoms with excess electrons are negatively charged. Atoms with electron deficit (excess 'holes' in their valence shells) are positively charged

To understand properly then you need to read up on some chemistry and electron shells and valence electrons.

An NPN transistor has 3 layers of semiconductor in the order N-P-N.

You can hook that up in the opposite direction and it also reads N-P-N backwards. Based on the very simplistic diagrams, you could treat the emitter and collector terminals ( the two 'N' ) in the opposite way, and it would work backwards. But actually, in real transistors, the layers are not symmetric and that doesn't actually work.

You can actually use transistors in a backwards fashion, but there is not a real lots of point unless you are trying to do something special and know a lot more about it.

Holy cow, there is quite a bit of reading here.

http://jacquesricher.com/NEETS/

Are they training technicians or design engineers?

That makes me sad that you said that.

I've worked with a few so-called ETs that don't know even a fraction of that stuff. I've worked with techs who don't even know what is contained only in "Module 19 - The Technician's Handbook".

The head tech at one TV shop where I worked couldn't read color codes and could not even apply Ohm's law. A few times, people came in wanting to know how to hook up an LED indicator in there car. He would go looking for a service manual for something that had an LED that ran off of 12V, and tell them that resistor value.

If you are doing this as a hobby, then learn as much or as little as you like. I don't look down on anyone who learns what they need to know to complete a project. After all, I only know enough about my vehicles to do minor maintenance, not become a mechanic, and I only know what I do, about the vehicles I've driven.

But if you actually want to work and earn the title of Electronics Technician, you should at least be familiar with the entire book. You never know where the field will take you.

And there is a lot more to electronics than what is in that book. And you need to know way more than what is in that book to actually be an EE.