Timeline for How can I fix a conceptual misunderstanding about BJT transistors in saturation?
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| Feb 20 at 9:07 | comment | added | LvW | @ Justme - I am afraid there was a misunderstanding. I could not imagine that you (with the term "two-diode model") was referring to the simple diode combination in post#1. I did not understand this drawing as a complete model of the questioner, but rather as an illustration of the problem discription. Rather, I thougt that you were referring to the figures as given in the contribution from periblepsis (including also two diodes). Misunderstanding clarified. Thank you. | |
| Feb 19 at 16:17 | comment | added | Justme | @LvW The question is asking about a transistor modeled as two diodes - nothing else. So that model with two diodes cannot explain how base current going to emitter makes the current flow from emitter to collector too. And that's because two separate diodes are not a transitor. | |
| Feb 19 at 15:30 | comment | added | LvW | contd: And what happens at Vce=0? The current Ic assumes some negative values - this is the current through the B-C junction. | |
| Feb 19 at 15:27 | comment | added | LvW | @ Justme - Quote:"So the model does not even try to explain how a transistor works in saturation,." Sorry, but I cannot agree to this statement. In saturation, both pn junctiones (B-E and B-C) are forward biased - and the base current is increased corrispondingly. More than that, look at the set of curves Ic=f(Vce) in the saturation region. The value of Ic decreases rapidly - Why? Because the current through the B-C junction is opposite to the "normal" Ic direction. At app. some tenth of mV (for Vce) threse two currents compensate each other and the net Ic crosses the Vce axis with Ic=0. | |
| Feb 15 at 11:01 | history | edited | Justme | CC BY-SA 4.0 |
added 409 characters in body
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| Feb 15 at 9:24 | history | answered | Justme | CC BY-SA 4.0 |