Claude,
When you say that the diode equation uses voltage to define current, are you referring to Id = Is*exp((Vd/Vt)-1)? Are you aware that the same equation can be written as Vd = Vt*ln((Id/Is)+1)? Just as current is an exponential function of voltage, voltage is also a logarithmic function of current. The equation is usually introduced in I vs. V form to emphasize how a small change in voltage accompanies a large change in current. There is no pecking order here. In Ohm's law, V = I*R, I = V?R< & R = V/I, all say the same thing.
Yes, I am aware of inverse relationships. My point is that Vbe and Ic are tied together by a relatively simple equation that does not involve QM to express. I iterate that I would not design a BJT using that equation, however.
Since Ib & Ic change before Vbe, how can Ib/Ic/Ie be consequences of the change in Vbe. The consequence cannot occur before the controlling quantity. As far as a higher Vbe increasing Ic, again, the external stimulus increases Ie & Ib first, then Ic & Vbe increase as consequences afterward. Vbe is not controlling Ic, rather Ie is controlling Ic. The sequence of events affirm this. The notion that Vbe controls Ic is one you cannot demonstrate w/ semicon physics, you just dogmatically insist upon it. I'm at a loss to make that clearer.
I don't agree that Ib & Ic change before Vce. I would think they changed together. You are right, I cannot imagine one of those variables changing before the other.
Which prof are you referring to? The debates in my undergrad years were not with any prof. An undergrad ME student once told me that V comes before I. He also told me that electric cars should use generators to recycle energy. When the battery is driving the motors, he felt that adding a generator would replace some of the energy, allowing for extended battery life. Attempts to show him why that won't work were futile. My profs always emphasized that I & V are circular in relation to each other. Neither controls the other.
The one I referred to earlier. Here is his website.
**broken link removed** . He responded to me with a email when I asked him if a BJT was CC.
Ratch,
I hate to be the one telling you this but the BJT is indeed a voltage
controlled device. The voltage applied to the base emitter junction controls
the collector current and the base current is a result of the additional
hole injection (for an npn BJT) into the emitter as well as the
recombination in the base-emitter depletion region and the quasi-neutral
base region. It is tempting to claim that the BJT is controlled by the base
current, since that is how a BJT is typically biased; the exponential
variation of the current with the base-emitter voltage makes a voltage bias
impractical. Any circuit designer will also tell you that any voltage bias
can be replaced by its Thevenin equivalent current source. Hopefully this
provides you some ammunition to claim that either one can be claimed when
treating the device as a black box. Finally, you'll find that a MOSFET
biased in the subthreshold region has characteristics that are very similar
to that of a BJT.
Bart Van Zeghbroeck
Professor
University of Colorado
Department of Electrical and Computer Engineering
Campus Box 425
Boulder, CO 80309-0425
Office ECEE1B41
Tel: 303-492-2809
Fax: 303-492-2758
Email: b...@colorado.edu
The ME you referred to was off base, of course.
Do you develop hardware? What field if so?
No, I do not.
Have you studies semicon physics?
Yes.
You cannot address the energy issues. You ignore the fact that a change in energy requires both Ib & Vbe.
I agree it does. And if the BJT has a higher β, then it requires less energy, less current, but the same Vbe.
It's pointless to continue. People reading this thread will hopefully know that OEMs have a reason for their positiions. They can research this matter themselves, & learn why the CC & QC models are employed for the bjt.
Certainly they can.
Ratch