Hi,
From your #59:
"How can VBE determine the current IC when it is (a) not known exactly and (b) assumed to be a constant value ??"
Here I repeat what I really have written in my post#59
".....very often I`ve heard the question (not only from beginners):
How can VBE determine the current IC when it is (a) not known exactly and (b) assumed to be a constant value ??"
As everybody can read - I have quoted a question I often have heard from other persons.
And what are you doing? You give the impression as if that were my statement.
OK - no chance for a fair exchange of arguments. I stop the discussion now because you are falsifying my words.
Bye
LvW
Hi,
Well, i have to chuckle a little there :-)
But i do apologize if i misquoted you. It is harder to talk about something so specific in a message board forum because we can not correct each other right away, it takes sometimes 1/2 day or even a full day before one or more of us can get back to reply. I've also had a host of other things going on in my court the last week or so that demand a lot of attention so being preoccupied does not help at all.
But be sure i am not trying to 'falsify' your comments, if anything i am trying to verify and understand what you were saying. However, we all have our way of looking at things and i dont think your view will change much and i dont think my view will change much, and i think the only reason we got into this discussion in the first place was because we dont understand each others points of view entirely. For example, it's not the first time i have heard the "voltage controlled" idea come up in BJT analysis, and i reject it outright for a number of reasons, and some of those reasons have to do with the history of electronics and how hard it is to change the trend that follows in those footsteps. [Note: of course i meant not voltage controlled only not that we can never use the voltage control idea.]
Because i have studied this problem in detail before, i should have just stated from the start that probably the only way i would accept a 'final' definition of what causes one or the other (voltage or current, or as we say charge) is a proof that there is a *delay* in one when the other somehow appears by itself without the other. In the context of this discussion, that would mean i would have to see a proof that voltage can appear all by itself, and then sometime later, even if it is such an extremely tiny time period later, that then and only then does the charge start to move (or current starts to flow). The delay i am talking about here could be on the order of 1e-30 seconds, and even though that is probably not measurable i would still accept that if a good proof was shown.
But to add to that, i would then have to take that argument and *apply* it to a circuit and try to determine if it has any practical significance. If we can *never* measure that then there is no practical significance, at least probably not in our lifetimes. At some point technology may be able to measure such an extremely short time, at which case it *could* become significant, but for our time it may not be so.
So to convince me there is only one way that i know of, and that is to show that there is at least sometimes a delay between the time that a voltage appears to the time that charge begins to flow. Once we have a numerical figure to work with we can then go on to determine the practical significance, if any. Without that extra step though i could still probably accept that there is at least some time no matter how small, but i would have to at least see that there is some time delay.
Since we are talking about an electrical behavior, we also limit the discussion to electrical behavior alone without the possibility of mechanical or other types of intervention. A photo transistor will obviously change the properties because of the photo electric effect, but we block all light from reaching the transistor junctions so we can concentrate on the purely electrical (voltage and current) properties alone.
So show me that and i will probably be at least partially convinced. Of course if that were to happen, we would then have an awful lot of data sheets to change :-)
Since this probably isnt going to happen, i will respect your decision to not discuss this any further. I realize that it would be very hard to prove this without a good lab unless we could find someone else who did work in this area already, which could be a possibility, and then we would just have to find that work.
BTW an analogy may come in the form of a purely mechanical system. We have a hard, small ball that is on a frictionless surface and we apply a force to one side of the ball. What comes first, the force on the ball or the movement of the ball?
Amazingly, with no friction (inertia only) from the moment the force is applied the ball BEGINS to move, and there is no delay in this process. In fact, i think dynamic friction would not change that either however static friction would because it would hold the ball in position until some significant non zero level of force was achieved. So again we see no delay between one thing and the other, between the applied force and the movement of the object.