> there is always a forward-biased junction between the collector and the emitter, creating an unavoidable 0.6 V loss for any loads you are planning to drive
Ha! As I was reading, I did wonder why you jumped right to FETs, but it makes sense. (Smart not to follow the historical timeline as most authors do.)
When I was young and there was no internet, I struggled with the solid-state physics behind BJTs. The valance band diagrams made no sense and weren't well explained. The in-depth analysis of carriers and holes overwhelmed me with detail. And in retrospect, most accounts didn't make clear the importance of the *thinness* of the base, that BJTs worked in part because of a *mechanical* effect. It was years before I understood that. (Kudos for mentioning it here!) In contrast, FETs were easy. A lot like triodes.
It wasn't until I took a functional approach that I could design with BJTs. Emitter-base is a diode. Emitter-collector is a magic valve that depends on the diode current. That was all my simple designs needed to know.
One of the most important part is two paragraphs between "From the diagram, it should be clear..." and "...if the current flowing through it isn’t limited in some way."
I've majored in physics, particularly electronics, but I still need to stop and think carefully, in steps, what those two paragraphs explain and why. I guess a bit more detailed explanation and maybe a picture could help.
Interesting article, good explanations but the shot of the 2N1412 in the opening pic is misleading being a Germanium device and not explaining the differences between Ge and Si and the limitations that made Silicon a better choice for ICs.
Yeah, the discussion of different semiconductor materials and dopants is probably well outside the scope of this article, but it's an interesting topic. I did include a caption under the photo noting it's a germanium transistor, but didn't really say more.
I don't think this is true:
> there is always a forward-biased junction between the collector and the emitter, creating an unavoidable 0.6 V loss for any loads you are planning to drive
This drop happens only in Darlington transistors, as they need to feed the second junction from it. In standard "single" BJTs, the drop across the transistor (Vce) scales linearly with current (Ice), starting at almost-zero. There are some plots in this stackexchange: https://electronics.stackexchange.com/questions/582833/transistor-collector-emitter-saturation-voltage
Yes, that was a brain fart, thanks for pointing it out! Back in the day, I spent too much time working with Darlington drivers such as ULN2003.
Ha! As I was reading, I did wonder why you jumped right to FETs, but it makes sense. (Smart not to follow the historical timeline as most authors do.)
When I was young and there was no internet, I struggled with the solid-state physics behind BJTs. The valance band diagrams made no sense and weren't well explained. The in-depth analysis of carriers and holes overwhelmed me with detail. And in retrospect, most accounts didn't make clear the importance of the *thinness* of the base, that BJTs worked in part because of a *mechanical* effect. It was years before I understood that. (Kudos for mentioning it here!) In contrast, FETs were easy. A lot like triodes.
It wasn't until I took a functional approach that I could design with BJTs. Emitter-base is a diode. Emitter-collector is a magic valve that depends on the diode current. That was all my simple designs needed to know.
One of the most important part is two paragraphs between "From the diagram, it should be clear..." and "...if the current flowing through it isn’t limited in some way."
I've majored in physics, particularly electronics, but I still need to stop and think carefully, in steps, what those two paragraphs explain and why. I guess a bit more detailed explanation and maybe a picture could help.
I think you're right; I ended up rephrasing these paragraphs a bit, although I'm not sure I'm 100% happy.
Interesting article, good explanations but the shot of the 2N1412 in the opening pic is misleading being a Germanium device and not explaining the differences between Ge and Si and the limitations that made Silicon a better choice for ICs.
Yeah, the discussion of different semiconductor materials and dopants is probably well outside the scope of this article, but it's an interesting topic. I did include a caption under the photo noting it's a germanium transistor, but didn't really say more.