OT: Is this question too challenging for a BSEE graduate?

That was my initial response, where the FET was the "programmable load", hence my other post.

It is a good quiz for fun, but not a good interview question. What does it prove? The candidate is a good quiz solver? It has no real engineering use. Are they hiring quiz solver or engineer?

Possibly. I took my formal electronics classes over 35 years ago. One of the instructors was an EE who couldn't understand the need for bypass caps on the power supply lined of boards using TTL ICs.

Any electronics technician should be able to solve this by inspection; no calculator necessary. 3K/1k = x/40, therefore x= 120 ohms. Come up with more difficult ones next time.

PlainBill

It's a great interview question. It shows whether the candidate can cut through the clutter and see the basic principle involved. A good engineer needs to be able to do that.

But do you base your hiring/firing decision on whether he can do it during the interview? Most engineers can solve it in more relaxed environment, in the real world. It only proved that many can't do it under pressure, during the interview.

On 10/22/2010 7:59 PM RosemontCrest spake thus:

OK, I freely admit that I do *not* understand how op-amps work and can't figure out this puzzle. (I hope to someday.) I'm just keeping score here on this thread.

So if this is so all-fired obvious, why are we getting different answers?

A. 153.8 ohms B. 120 ohms

Both can't be correct, obviously. Which one is?

..

What do you mean by "inspection"? Are you applying a formula you memorized? Or do you /understand/ what's involved?

Maybe the OP is showing the new hire what to expect from the new manager.

Silly tests like this shows how a manager will behave after being hired.

These tests work both ways.

eer

Yes, usually they are sweat shops hiring slaves.

Interviews can be unnerving. Well-qualified people can collapse under pressure. You would never use a single question, nor would you make the answers to even a series of questions the basis for hiring or firing.

I don't mean to be offensive, but it you /understood/ the principal of anaysis -- which is actual quite trivial -- there would be no question.

The resistance of the JFET itself is 120 ohms, which is what we're looking for, regardless of how the question is phrased.

I had first hand experience. I got stomped-on by similar quiz by a junior engineer. After that, i had no intention of taking that job and no interest in continuing the interviews. I should have just walk out at the point. It was a total waste of my time and their resources, but dinner was good and the company paid.

Sorry. Q1 is a MOSFET in the test I give applicants. I replicated the circuit at home and erroneously picked the first N-channel FET I found.

On 10/23/2010 2:31 PM William Sommerwerck spake thus:

Well, duh. Obviously, I don't. Perhaps someday I may.

So I ask, perhaps naively: is this basically the same as finding the Thévenin equivalent of the circuit?

Oh, OK: Vcd/(((Vdc/4)/40) A).

Hope This Helps! Rich

No. In fact, one of the things the testee has to recognize is that this question has /nothing/ to do with the Norton or Thévenin equivalents, and you're only going to confuse the hell out of yourself if you go in that direction.

The principle is this... In a stable op-amp circuit, the feedback forces the inverting and non-inverting inputs /to have the same voltage/. The rest is trivial arithmetic.

hamilton wrote in news:i9vgc0$l99$ snipped-for-privacy@news.eternal-september.org:

At least its technical.When I first graduated I had an interview with a large comunications corp and not one question had anything to do with electronics. I think the HR department gets their interview questions from COSMO. I felt like I was answering one of those dumb womans magazines quizes.

My experience was the smaller comapainies tended to be more intrested in your technical understanding the larger ones seemed more intrested in your psych profile.

I choked on one 6 guys asking me to reproduce the LNA I did in school I think I screwed up all my symbols and couldnt explain the bias network ;brainfart.

Oh well it all worked out OK I make more money now then any of those jobs so no compalints.

On 10/23/2010 3:47 PM William Sommerwerck spake thus:

Aha. Nice trick question, that.

So I learned something today. Thanks for your patience.