AMD
3.1 of 5 1,048 reviews
www.amd.com Sunnyvale, CA 5000+ Employees

AMD Senior Design Engineer Interview Question

I interviewed in Austin, TX and was asked:
"In saturation, the channel region pinches off well before the drain. How does current get from the source to drain then? (Since the channel is pinched off, it does not touch the drain)"
Tags: technical
Add Tags [?]
Answer Flag Question

Part of a Senior Design Engineer Interview Review - one of 239 AMD Interview Reviews

Answers & Comments

0
of 2
votes
Tunneling
- Interview Candidate on Feb 25, 2009 Flag Response
5
of 6
votes
Its drift, there is an electric field across the depletion region, whenever an electron diffuses into the depletion region, the electric field sweeps it across the the drain, the current thus depends on the diffusion into the depeletion region rather than the electric field strength so current is relatively constant in saturation.
- Anonymous on May 14, 2009 Flag Response
1
of 1
vote
This is an excellent question and the last answer by anonymous is very correct. I will try to elaborate further. Now, when the channel is pinched off, this is due to an extension of the depletion region between the drain and the bulk into the channel region, thus due to the large(+ve) E field from drain to source, Electrons are swept into the n+(drain) region, thus u have drift current due to this movement! Now technically speaking, whenever you have a depletion region btw the N+ and P material, the current flow contribution is not only due to Drift, you have Diffusion contribution also but is assumed negligible compared to Drift current!
- Leo on Aug 17, 2011 Flag Response

To comment on this question, Sign In with Facebook or Sign Up


Tags are like keywords that help categorize interview questions that have something in common.

Glassdoor is your free inside look at AMD interview questions and advice. All interview reviews posted anonymously by AMD employees and interview candidates.