no, or not always, or not anymore ;)

-first of all, the 1% and 5% being tolerances , are usually specified either
at standard temperature (like 25deg C) , or across temperature range. IF the
specs are at 25deg C , they don't imply any kind of temperature performance
. There will be no relationship whatsoever between a resistor being 1%
across temperature and being sold as 1% tolerance. Life is not that easy.
There might be different temperature coefficients involved depending on the
resistors' technology but that's another story ,they might even be
non-linear with temperature .
-long ago ,when resistor materials manufacturing costs were the predominant
part in the resistor retail price (or so the legend said) , some vendors
used to sort their resistors . That way, they were making only 5% parts.
They were picking the parts which were within +/-2% and +/-1% from the 5%
batch and marked them as 2% and 1% . I recall someone having "fun" one day ,
plotting a whole resistors box distribution only to figure out if they were
selected as 1% or unselected. The idea was that if they were unselected, we
could've selected them for 0.1%, otherwise the middle of the curve was gone
and sold as 0.1% . Now, time is  a lot more important than materials for
resistors , processes are a lot more under control, so I doubt any resistor
manufacturer  is selecting 1% out of the 5% bin. They might do it for
specialty parts , low volume and/or low yield high precision parts but not
the 5%.

- as a sidenote, the cherry picking procedure makes Monte-Carlo analysis
somewhat useless, unless the problem was trivial . That is because the
cherry picked parts don't obey any random distribution curve so the
combinations Monte-Carlo is calculating in that case don't really exist.

Best Regards,
Matt Tudor , MSEE
http://www.gigahertzelectronics.com


----- Original Message -----
From: "Andy Gulliver" <[EMAIL PROTECTED]>
To: "Protel EDA Forum" <[EMAIL PROTECTED]>
Sent: Tuesday, July 02, 2002 6:44 AM
Subject: Re: [PEDA] AW: SPICE sim question


> Also, in practice you'll be very lucky to find a resistor sold as 5% that
is
> within 1% across temperature etc. - they're the ones that are being sold
as
> 1% parts!
>
> Regards,
>
> Andy Gulliver



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