I think any circuit designer would be very delighted to have such a simple model to get insight and estimate performance. However, I'm of the opinion that every model, however simple it might be, should not only be useful to understand things qualitatively, but also quantitatively, otherwise it'd be useless.

I see a few incongruencies with this paper. For instance, you start by saying that you'll explain the transistor behavior using the concept of "dynamic resistance", but then you talk about the transistor changing its static resistance. I guess you want to say that "static resistance" becomes dynamic, or something. Next, you say that the current will be kept horizontal in the graph, but you also use the qualifier "almost". If we take this "almost" qualifier seriously, then your model breaks down, and we return to the usual small-signal output resistance that we all know.

Finally, if students would take home the idea that transistors can keep their current rather constant, then...

(cont.) they'd think that one can simply make a current source by fixing a voltage at the gate and that'd be it. Obviously, we all know that cannot be further from the truth. I wonder how they'd feel after learning that feedback is needed to achieve such ideal behavior.

Finally, I must say I had never understood Einstein phrase "Make everything as simple as possible, but not simpler". However, with all due respect, I think this article is the first example of this phrase.

Perhaps I'm missing something, maybe you can enlighten me. But as I see it, I don't see anything useful in this very simplified model you've come up with.

@ErnestoG‭, I apologize for the late reply. You have correctly grasped the essence of my idea, but as a circuit designer, you don't see the point in it because it is qualitative rather than quantitative.

My goal is not to directly use it for calculations and design, but to achieve an intuitive, functional understanding of how a transistor maintains a constant current. This is no less important than the other aspect, and people need it as well.

You have correctly guessed that by 'dynamic resistance,' I mean a 'changing static resistance'. The word 'resistance' is not very suitable in this case, as it creates an association with a linear ohmic resistance. Perhaps 'opposition,' 'resistivity', 'conductivity' or something similar would be better.

Thanks for the response,

Regards,

Cyril

Circuit fantasist‭

Well, I disagree, but I guess everyone has its own way to teaching. If we're trying to simplify explanations and not looking for calculation-worthy models, why not say directly:

In triode region the transistor functions as a resistor, and in saturation, it behaves as a current source. That simple.

Students at that level should already know how a resistor and an ideal current source works I suppose. Why go for a crutch-like explanation that is not true anyhow in the real-life? It seems to me you've found a way to explain the behavior of an axiomatic circuit block (the current source) with another one, the resistor. Feels unnecessary in my opinion.