4 ms·
As always these things tell us how transistors work, which is fine and all that, but that's not enough to tell anyone how to use one which is almost universally
by gw99 4y ago
As always these things tell us how transistors work, which is fine and all that, but that's not enough to tell anyone how to use one which is almost universally done incorrectly even in some high profile textbooks. They are a little more complicated than this video can muster. In fact I'd argue that it's probably worth skipping this and delving into the mathematics properly.
Wes Hayward W7ZOI explains this side of things rather well in his book Experimental Methods in RF design. Some of the content is duplicated here discussing bipolar transistor feedback amplifier designs: http://w7zoi.net/transistor_models_and_the_fba.pdf http://w7zoi.net/transistor_models_and_the_fba.pdf
- JKCalhoun 4y agoI like the free "200 Transistor Circuits" book. Here is one link for it, there are many others if you Google: https://github.com/rhaido/200_transistor_circuits_united/blob/master/200_transistor_circuits.pdf https://github.com/rhaido/200_transistor_circuits_united/blo... Also he did a free book with fifty 555 circuits: http://www.talkingelectronics.com/projects/50%20-%20555%20Circuits/50%20-%20555%20Circuits.html http://www.talkingelectronics.com/projects/50%20-%20555%20Ci... And 100 IC circuits: http://www.talkingelectronics.com/projects/100%20IC%20Circuits/1-100_IC-Ccts.html http://www.talkingelectronics.com/projects/100%20IC%20Circui...
- omnicognate 4y ago> almost universally done incorrectly even in some high profile textbooks In what way(s) do books tend to get it wrong, and is "The Art of Electronics" by Horowitz and Hill, which I'm currently reading, free of such errors?
- exmadscientist 4y agoHayward's "more detailed model by Ebers and Moll" features prominently in AoE. So don't worry about them. The cardinal sin of teaching BJTs is to say that they're current-controlled amplifiers: little current in, big current out. They are not, not really. They're voltage-to-current converters: little voltage wiggle at Vbe, big current wiggle at Ic. This is really not in dispute and anyone who tries to argue for the hFE/beta model as really true is wrong. Certainly, it is a useful approximation and often all you need, but it is not how a BJT really works and so don't pretend it is. (The link between the two is that the base is not a high impedance input. That is pretty uncommon, so it's not surprising that it's kind of confusing! Because it's a low-impedance input, small changes in applied Vbe correlate directly with small changes in current, so it looks current-controlled. But careful measurements, as I believe are plotted in AoE, reveal the primacy of the Vbe-controlled model.)
- omnicognate 4y agoThanks! That's very helpful.
- gw99 4y agoThis is a really good description without delving into the mathematics.
- gw99 4y agoOther commenter has it spot on. TAoE is a good reference so carry on reading :)