[time-nuts] Simulation

J. Forster jfor at quik.com
Sat Aug 14 15:08:56 UTC 2010

FWIW, IMO any engineer who uses undocumented or uncontrolled parameters or
instructions in a production design is a fool.

If you are that silly, you must fully specify the selection criteria.



> Bob Camp wrote:
>> Hi
>> Simply a few stories I thought I would share.
>> Simulate design. Use manufacturer's published models. Build design. Note
>> differences. Call manufacturer. Answer - switched die three years ago,
>> Ft is now " much better " ( now 3x old parts ).
>> Odd they never mentioned that to people who work for the same company.
>> Simulate design, Build design, verify design, ship it for a few years.
>> Odd things start to happen. Look at some parts. Package looks different.
>> Ask around..... Line got moved to other side of big ocean. Process got "
>> tweaked" beta is now 4x what it was.
>> Again all inside the same company. Both cases were excused by industry
>> standard specs that had no upper limit.
>> We had whole departments devoted to tracking this sort of stuff. It
>> still happened on a regular basis. 30 years later the specs on the
>> devices and their published models are still the " old version " ones.
> there are also designs that depend on "non-data-sheet" performance of
> particular devices.  There's a very low noise, very low leakage fet
> popular in charge amplifiers.  It has a JEDEC 2N number (which I can't
> remember off hand), but only the ones from one particular company (in
> England) actually work in the circuits, and even then, there's some hand
> selection involved.
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