See Bipolar junction transistor - Wikipedia.
You get (delta Ic / delta Vbe) by differentiating Ic and thus Ie with respect to Vbe. Due to the exponential law, 1/Vt appears as factor.
Matthias
Edit: Note that Ies is very small.
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again, test equipment will tell you exactly what is what for any parameter. No guessing needed nor approx. formulas nor using inaccurate spec sheets.
All are fairly easy except small C's under intended operating conditions.
THx-RNMarsh
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Can you please try and explain a little more with possible a mathematical example.
You can measure dielectric absorption, but what does it sound like in the time domain or transient conditions? Seems like steady state measurements of distortion wouldn't show the whole picture.
This is just not generally true. Would that it were. What about rbb, for example?
Cheers,
Bob
As Ies is small, and Ie almost equals Ic, you may approximate
Ic = Ies * exp(Vbe/Ut).
Now, gm = (Delta Ic) / (Delta Vbe) is given by the differential quotient gm = (d Ic) / (d Vbe), and you have
(d Ic) / (d Vbe) = 1/Ut * Ies * exp(Vbe/Ut) = Ic / Ut
from differentiation (exp(x))' = exp(x) and chain rule of differential calculus.
Matthias
Edit: cross-post with previous post. Better to save the effort?
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Thanks for your efforts matze.
So your formula Ic = Ies * exp(Vbe/Ut).
Is the same as the one at the top of page 17
Ic = Is * exp(Vbe/Vt).
Or is les something different to Is and Ut something different to Vt.
Just a bit confused with the different variable abbreviations of the variables
In some countries, we do not have letter "V" in the alphabet, therefore we are forced to use the letter "U" instead to label the voltage.
Hence Vt = Ut.
And transconductance gm is the slope of the function Ic = f(Vbe).
And in math, the slope is a differential quantity dy/dx. For a straight line we have Slope formula (article) | Slope |
Khan Academy
For a given DC Ic current the slope of the function Ic = Is * exp(Vbe/Vt) is gm = Ic/Vt
Hence Vt = Ut.
And transconductance gm is the slope of the function Ic = f(Vbe).
And in math, the slope is a differential quantity dy/dx. For a straight line we have Slope formula (article) | Slope |
Khan Academy
For a given DC Ic current the slope of the function Ic = Is * exp(Vbe/Vt) is gm = Ic/Vt
Yes, Ies is the same as Is in Bob's book (see also the Wikipedia reference from the earlier post). Sorry for mixing U with V; in German "engineering slang", U is often used for voltages.
Matthias
Thanks for that, Jony. We ideed have a "V" in the alphabet; do not know, where the convention of "U" for voltages stems from. Clearly off-topic for this thread ;-)
Matthias
Actually, I sort of mis-read your assertion as being that one can measure anything with a curve tracer. Now I realize you were saying essentially measure anything with test equipment. The latter is closer to being true, although even then for some parameters one must design some kind of test jig or test circuit to allow off-the-shelf test equipment to measure the parameter that one needs. Let's just agree that, by itself, a curve tracer is not the answer to the maiden's prayer.
Cheers,
Bob
Yes, it is going very well. The final manuscript will be complete in April. The second edition should be out before the end of the year. It will have 36 chapters and be about 750 pages long.
Cheers,
Bob
Congratulations, Bob! If you and your wife happen to enjoy our local agricultural product from NorCal where I live (grape juice), I would be thrilled to send you a few of them as a Thank You on behalf of all DIYaudio members everywhere!
Mark Johnson
a fan
*they store the grape juice in oak barrels a few years, for improved sensory enjoyment.
Mark Johnson
a fan
*they store the grape juice in oak barrels a few years, for improved sensory enjoyment.
yes, curve tracer and a few other basic instruments. From following here -- so often it appears one cant trust the spec sheets and much is missing. So, when in doubt -- measure.
BTW - a flexible curve tracer like TEK models can do an amazing array of tests when configured and setup properly.
THx-RNMarsh
Nice... well done bob... really looking forward to this... hopefully we can pre order at some point.
Hi Damir,
I have not yet had a chance to look at it in detail, but a quick look suggests that your OITPC scheme and your simulation results show some promise. Thanks for sharing it!
Cheers,
Bob