cupido at mail.ua.pt
Sat Aug 14 15:32:20 UTC 2010
(in production yes I agree)
In research things are different.
You wouldn't mind to make an selection of fets or else
to obtain the very top specs of a certain unique instrument
design as the real final product are the results you
may obtain with that instrument and not at all it's design...
So many nice stories about gear that worked only with a certain set
of parts way off the manufacturers expressed data...
one day I'll drop a few here just for amusement.
J. Forster wrote:
> 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:
>>> 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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