MrAl - I can fully agree to the first two paragraphs of your last contribution.
However, I have some objections against the rest of the text. Let me explain:
Quote: In this same way I find it hard to say that the voltage is 'controlling' the transistor, however I dont have a problem with saying that the voltage is the principle mode of operation. That is, certain things would happen as long as we maintain the voltage at the exact same level throughout, and do not try to change the current.
I cannot agree. The question if we are able to „maintain the voltage at the exact same level“ has nothing to do with physical determined properties of a device.
Quote: The catch we could run into when trying to say that it is 'controlled' by the voltage is if something else changes that is NOT under our control, we loose that control and we must change the drive signal to make up for it, and that is really controlling the transistor,
I am afraid that the working principles of a device do not depend on any changes which might be not „under our control“. In this context, may I direct your attention to the pdf figures I have attached to my reply’27 ? I think, the figures (stabilization lines) give an answer.
For my opinion, it would be a good thing when each designer of a BJT amplifier stage would be able to know the function of each part he is using.
Therefore - again my question:
How can the primary reason for using an emitter resistor RE (stablizing IC against unwanted changes, uncertainties and tolerances) explained WITHOUT using the relation between IE (resp IC) and the voltage VBE?
Interestingly, I did get no answer in this thread up to now..
(The same applies to all other technical facts - verified by measurements (!) - I have mentioned in this thread supporting voltage control).
MrAl - may I ask you: What is your answer?
Hi again,
Interesting reply.
First about the emitter resistor...
I will say what i have said all along for the practical case, and that is that the type of analysis depends on what we want to know. In some cases it is easier to use a voltage based equation and sometimes it is easier to use a current based equation.
I could have asked an equally valid question which would depend on knowing the base emitter voltage more so than the current, and that is in the practical case of the 'normal' voltage reference diode. We use voltage because we care more about the voltage than the current. If we cared more about the current we might want to know what the base current is, and knowing the spread of Beta we can design something that is independent of Beta. However, we also can not forget that although we dont care as much about the current, the current still assumes whatever level it needs to be for the given device and that current will change with the voltage change.
Second to the point of "The question of if we are able to maintain the voltage at the exact level..."...
I actually said what you are saying too, but i only had a difference with what we called it, "control" vs "mode of operation".
My question to you is if you look at the two coil case (or even just two magnets really except that seems like there's no way to control it anyway) where we have the two coils facing each other and lets limit to the case where they are repelled by each other. We know it is the magnetic field that causes the repulsion, but do you think it is a good idea to call the effect of the magnetic field "controlling" something? For example, two magnets hanging by two threads each, suspended and repelling each other, is the magnetic field "controlling" the distance of separation?
So i agree that in order to understand the characteristic behavior we may use a voltage oriented formula, i just dont think it is a good idea to call it "controlling" just like with the magnetic field and the two coils or two magnets.
You can look up the definition of 'control' and see what you think. I was going to ask if you could find other instances where it makes sense to call it controlling (other than the transistor) but i am not sure if i would be willing to accept them unless they made sense.
For the MOSFET, it is called, "voltage controlled", and most of us agree to that even though we can NEVER change the output without adding or taking away something physical from the input, which as we all know must be in the form of a current.
It is also interesting that this is the sole thing that causes so much confusion to people just getting into the field of electronics. When they go to use a MOSFET, they almost always think that they can drive it with a 1 megohm resistor even if it has to switch at 100kHz. What causes that confusion? It's the description of the MOSFET as being "voltage controlled" and having high input impedance (another misnomer).
I realize that it is sort of a convention of sorts though to call something voltage controlled. But i would bet we can not find one practical circuit that does not vary the voltage at the gate or base and thus the current as well.
So what do you say about the two coil or magnet example and the magnetic field? Are the two magnets "field controlled" or not?
BTW you have kept this interesting :-)