Alt-BEAM Archive
Message #05199
To: beam@sgiblab.sgi.com
From: Steven Bolt sbolt@xs4all.nl
Date: Fri, 9 Jul 1999 16:59:31 +0200 (CEST)
Subject: [alt-beam] Re: Something funny with the 1382 voltage triggers?
On Fri, 9 Jul 1999, Bob Shannon wrote:
> > You exchanged parts for equivalents and the design can't tolerate
> > that. Doh. It should not only be indifferent to the changes you
> > made, but also accept a wide range of solar panels, storage caps
> > and motors. Else it isn't much good, imho.
>
> Wrong yet again.
>
> I used the same parts, not equivalents. You may wish to beleive
> otherwise, and assume that the emperical evidence points in some
> other direction, but the circuit is not reacting to opinions.
If they were the same, your circuit would give the same
performance. So they aren't quite the same, are they?
But they would be the `same' if the designer takes care to make his
stuff work according to specs, despite the normally expected large
component tolerances. I've been using thru-hole for development and
SMT for the real thing for years. I see no reason for trouble at
low frequencies (up to tens of MHz at least), as long as power
dissipation is kept in mind. Never had trouble, and I use merely
equivalent types, with different numbers.
> Normally expected tolerance, with the same parts?
Yup. For instance, BC337 is tabled as having an hFE between 100 and
600 @ Ic of 100mA. Specifying for instance the BC337-25 narrows it
down a bit - to between 160 and 400 at the same Ic. I'd call that
pretty large tolerance, and it is between one thru-hole transistor
and another with exactly the same markings. If I understand you
correctly, the silicon in your SMT transistors differs from what's
inside your thru-hole parts.
Btw, if you are sure they are the same, why bother comparing them
with a curve tracer? Am I missing something?
Best,
Steve
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# sbolt@xs4all.nl # Steven Bolt # popular science monthly KIJK #
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