Re: gEDA-user: ngspice shot noise

[Gene Heskett <gene.heskett@xxxxxxxxxxx>]

On Sunday 02 October 2005 15:22, Karel Kulhavy wrote:
>> 2N3904's appear to be the leftovers from a lot of processes. I
would
>> not implicitly trust any one spec to be within +-100% of the spec
>> sheet.
>
>But if it isn't, I can return them to the shop because that's
deception
>of customer, isn't it?
>
>> I've not found them to be very long lived in lots of the stuff
where
>> the bean counters told engineering that 'its good enough'.
>
>What is the type of the transistor from which 2N3904 is a leftover?
>
>Is it possible that a transistor has short life because of being a
>leftover from process? What happens after the life? Stops amplifying
or
>what?
>
>CL<

In my 56 years of electronics experience, 33 as a CET, both high
noise levels and open junctions (or junction leads, aka bonding) and
even shorted junctions in a circuit that couldn't possible supply
enough power or voltage to cause a punch-through.

"Life" seems to be a general jacking up of the bottom of the "bathtub"
curve, made from infant mortality, then somewhat dependable, followed
by old age related failures.  Its the somewhat dependable area that
bothers me as the failure rate, in my experience, never reached the
100% dependable area in the middle years one normally expects of well
processed semiconductors treated well.

As to what they may be the leftovers of, I haven't a very good idea
as I've seen them in almost every variation of the to-92 sized epoxy
case made at one time or another.

I'd suspect that there may be a newer device that can do that job, and
be considerably less prone to biteing you in the QC dept, at not more
than another penny or 5 per device.  I'd drag out my books, but mine
are now dated as I'm almost retired at 71, so the references wouldn't
be whats out there today.  And you need whats out there today from
the sounds of things.

Good luck.

-- 
Cheers, Gene
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
99.35% setiathome rank, not too shabby for a WV hillbilly
Yahoo.com and AOL/TW attorneys please note, additions to the above
message by Gene Heskett are:
Copyright 2005 by Maurice Eugene Heskett, all rights reserved.