I draw it as NPN on a whiteboard. I don't write E/B/C, so I get to find out if he can name the bits of a transistor. The applicant is free to ask any questions, which gives me more info.
Surviving that, the problem is essentially identical to the one I posted, with a bit more base current.
One more question: What is the pressure of the magic smoke inside the transistor?
I'd be happy for the applicant to make some assumptions (stated, if he likes) and give me ballpark numbers. *Without* cranking up Spice on his laptop.
That information is only necessary for about half of the answers and changes them less than 10%.
...and that doesn't change 1/3 of the answers (but should cause some other unsolicited comments, if PNP). ;-)
Same answer.
If it's a jellybean NPN, the E-B junction is going to be just fine (typically they break down around 8-9V and are rated for at least 5V), and the answers are, as JL says, going to be about the same as his example except for the higher base current due to typically low reverse beta. But it fits a different visual pattern, being an NPN with E grounded-- it's probably not obvious that it's a "collector-follower".
Yes, I think MOST of us got that right away. The base voltage error may have been a misunderstanding as Vbe, but the saturation assumption was totally wrong.
But the point was that the followup posts seemed to ignore that fact, as
well as continuing to keep a huge amount of irrelevant quoted content. The suggestion to trim that was either missed or ignored, which implies ignorance, apathy, or intentional annoyance. Maybe all three! :)
Paul
Right - Didn't pay attention to the fact that the supplies are now positive...
That's way overkill for a first question interview. If some kid doesn't know about reverse beta, I wouldn't chuck him out right away.
I measured a BFT25 as having reverse beta about 4.
And each time some one comments on that, I still try to think of an application where that would prosper? Maybe something in speed switching . etc.. Kind of reminds me of ECL logic in a way.
Jamie
I have used a BFT25 to ground an AC-coupled analog signal, in a gain-switching application. You need a lot of base current to clamp the negative part of the swing, since reverse beta is low.
Why didn't you use a fet? Just askin'.
Some can't think without Spice, evidently.
Yeah, I didn't count the 5x5(mod10)=5. That should add another 408 0's, give or take a fence post.
Your messages are up to 607 lines of quoted text and blank double spaced lines. If you can't devise a method of fixing the double spacing problem, prehaps you might consider just deleting the quoted text in your replies so that your one-line aphorisms can be more easily excavated. Also, due to population pressure, global warming, and rampant speculation, white space is becoming a scarce commodity. We may soon run out of white space and allthewordswillruntogether.
snip (sorry)
Italian Seismologists?
Getting a manager to understand that doing nothing is the best course when something is running late - that's quite a feat.
Sylvia.
Right- there's nothing I can do about it, there are no text settings whatso ever, GG completely ignores its 'Quote Original' button, and it puts all th is double space junk in here just by hitting 'Post Reply'. And if I don't w atch it, it will send replies to the author too.
I'm increasingly wondering about how it would have ended up as an interview question. My best guess is the interviewer came across the problem and assumed, without doing it themselves, that it was reasonably simple - an intelligence test style question, rather than a maths question.
It took me a significant time to come up with an answer, and I would almost certainly have not succeeded when subject to the pressure of an interview - I function very badly under pressure :(.
Sylvia.
Sylvia.
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