Here is the core of the problem of this thread (post#1):
„When applying a current to the base pin to allow the current to flow from the collector to the emmiter(or vice versa) where does the current from the base pin go?...I haven't crossed any text that explains this clearly.“
??!?? what ? Ie = Ib + Ic . Any textbook on transistors will tell you that. where the hell did that question come from...
ah, i see original question.. man this thread has been taking some twist and turns and we are now waaaay off the original question.
However, you always should know what you are doing and, thus, realize that this is a model only. The physical reality is that the BJT is, of course, a voltage-controlled device (Ic=f(Vbe)). This is a proven fact.
The collector current is plotted in function of the base-emitter voltage , which is essentially a diode curve ( If vs Vf ). Once you have left the 'nik' in the curve ( to non linear section where the thing goes into conduction , you a have a relatively linear curve.
So you could say by modulating the Vf ( Vbe in case of transistor) you control the If ( Ic in case of a transistor )
Let's go back to the electron model ( forget the equations for now . this is elemental reasoning)
take an NPN Transistor in rest .
I apply an electron source between emitter and collector. Base is tied to emitter. I can try to accelerate the electrons by increasing the field strength ( the 'voltage'). In reality there may be a few stray electrons ( leakage ) and eventually the field per distance will get so large it will destroy the barriers and flash over with a fried lump of silicon as end result.
so, practically speaking no electrons flow ( electrons are charge carriers. flowing electrons are moving charge. moving charge is called current )
the structure between collector and emitter is NPN. two back to back diodes. we all know that diodes conduct current only in one direction. ( doesn't matter if we are conventional or electron model. ) put two back to back and you cant get anything through. no matter what polarity you apply one will decrease its recombination zone , the other will grow it.
nothing contradictory in my statements.
now. i will unclip the base from the emitter and connect to a second electron pump. i will slowly increase the field strength in an attempt to get electrons flowing. when i hit a certain field strength i will succeed in sending an electron across the recombination zone between emitter and base. if i keep increasing the field strength i will send more and more electrons into the base , removing the recombination zone there. This 'p' region now becomes flooded with electrons ( keep in mind this p region is very small in relation to the n regions of the collector and emittor. you cant just take one cubic meter of p material , a cubic meter of p and another cubic meter of n material and get a transistor. that doesn't work. even if you scale it down 3 decades to 1 millimeter of n , 1 millimeter of p and one millimeter of n again , it still wont work as a transistor. it only starts working at the micron level .
so , the base region is now flooded full of charge carriers running from emittor to base. this includes the part of the base region that touches the lump of collector material we called collector. the emitter-base field accelerates the electrons and some will start skipping the base ( which for them is a right angle turn so to speak ) and flow into the collector.
the conductivity of the base material is less ( the doping) than the collector.
This creates a relation between the number of electrons that go into base and the ones that go into collector. The emitter delivers a certain amount of electrons per second. assuming this is constant there will be a ratio between the ones that go into the base and the ones going into the collector. It is a self regulating mechanism . If too many go into the collector, the ones flowing out of the base decreases , starting to rebuild the recombination zone , so now less can enter the collector and more come back to the base. ( remember that our electron source delivers a constant amount of electrons per time unit. ) That is why flow of electrons in the base controls the flow of electrons in the collector.
Now you can try to slap names and labels and equations on that and you can write things in terms of applied field strengths or in terms of the ration of electrons. You can call these 'lost electrons' ejected through the base a parasitic current and you can do all kinds of other mathematical trickery. All that stuff works fine. some like it in terms of field strength , some like it in terms of coulombs per second.
One fact remains: that if no charge flows from emittor to base FIRST , that recombination zone between emitter and base does not disappear and electrons don't even get a chance to go into the collector. There will be no charge flowing in that pathway. the regulation mechanism is determined by the doping in the material .
So my statement remains : no base current is no chance of collector current .
Sure you can play with the field strength and write your equation in terms of the base emitter field. But the fact remains that it is this field that accelerates the charge carriers from emitter into base. if that charge does not flow from emitter to base , no charge will flow from emitter to current. moving charge is called current. negative charge carriers are electrons.
If you want to write stuff in terms of voltage control you will see that there is an 'offset' in your equations. That 'offset' voltage is required to get the current flowing.
Ic = f(Vbe) provided vbe > the field required to get it in conduction
you can eliminate the offset in calculations by switching to current model. if ib is zero then ic is zero.
you pick your poison.
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