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Topic: numerical challenge
Replies: 90   Last Post: Oct 26, 2012 7:41 PM

 Messages: [ Previous | Next ]
 Jeff Liebermann Posts: 13 Registered: 9/13/07
Re: numerical challenge
Posted: Oct 24, 2012 8:47 PM

On Tue, 23 Oct 2012 12:05:17 -0700, John Larkin
<jlarkin@highlandtechnology.com> wrote:

>You didn't want to work there, so it was a great interview.

Actually, I did want to work there, and probably would have been
willing to tolerate the manager. In retrospect, all he was doing was
defending his design and avoided hiring a potential troublemaker (me).

>This is my first-pass qualifier question.

I noticed that nobody actually answered the problem. So....
>
> +10V
> |
> C
>+5V--------------B
> E
> |
> 1K
> |
> gnd

>What is the base voltage?

5V

>What is the emitter voltage?

Assuming silicon, and not germanium,
5V - 0.6V = 4.4V

>What is the collector voltage?

10V

>What is the emitter current?

Ie = 4.4V / 1K = 4.4ma

>What is the collector current?

Assuming Beta = 100
Alpha = 100/(100+1) = 0.990
Ic = Alpha * Ie = 0.990 * 4.4ma = 4.36ma

>What is the base current?

4.40ma - 4.36ma = 0.044ma

>The best interview is to work on a real design problem, together on a
>whiteboard, for a couple of hours.

Agreed. The last engineer I hired (back in the early 1980's) was one
of maybe a dozen applicants that were filtered by HR. My boss gave me
about an hour each as he didn't want me to spend 12 days on
interviews. I wasn't hugely interested in what they knew. I was
interested in their willingness and abilities to learn new things. My
little memory test trick was my primary tool. There's not much that
can be done in an hour, especially with constant interruptions.
Eventually, about 4 people in engineering grilled the applicant. We
then compared notes and passed it on to whomever was going to make the
final decision. The overall batting average was lousy. We hired one
clown that instantly retired on the job. Another specialized in
finding excuses not to show up to work. Yet another acted like he was
still working for his previous employer. Spending a day with the
applicant would have brought much of this to the surface, but that
didn't happen.

There's also a problem hiring engineers in very small companies. At
literally all of my employers, engineers were directly involved in all
aspects of product development, production, QA, and documentation. We
needed a very versatile engineer, capable of doing more than just
engineering. I didn't care if the candidate knew how to do
everything. However, I did care if he was able to learn new skills. I
was hired at one company to do RF design work, but spent the first 6
months cleaning up my predecessors mess on the production line.

>I also like to ask people what they designed last, and to describe
>some circuits.

Yep. We also did that. However, I ran into one odd problem with an
engineer from Japan. I could see that he was competent. However, I
had great difficulty determining what he did at his previous employer.
It wasn't a big secret as it was all on his resume. Yet, he wouldn't
talk about it. I eventually determined that in Japan, he was
considered part of a team. Discussing a project without the inclusion
of the team was like taking personal credit for the teams
accomplishments. When I switched my questions to reflect the
accomplishments of the team, the answers were forthcoming.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Date Subject Author
10/22/12 Rich Delaney
10/22/12 Phil Hobbs
10/22/12 Rich Delaney
10/23/12 Phil Hobbs
10/23/12 G. Morgan
10/23/12 Phil Hobbs
10/23/12 Robert Macy
10/23/12 Frederick Williams
10/24/12 Robert Macy
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10/24/12 Spehro Pefhany
10/22/12 William Elliot
10/23/12 William Elliot
10/26/12 Rich Delaney
10/22/12 John Larkin
10/23/12 Jeff Liebermann
10/23/12 John Larkin
10/23/12 John Fields
10/23/12 Phil Hobbs
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10/23/12 John Fields
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