Re: Failed Transistor with Low h(FE)?


Chuck Harris <cfharris@...>
 

I have often wondered if many circuit designers
take these "holes" caused by factory robbery into
account when they specify their parts... I never
did, but perhaps the production guys would have
liked me better if I had?

You think you are using a 1K nominal part, +/-5%,
but in reality, your part is really:
[1.05K|0.95K] +/-2.5% of 1K

You thought you bought a one humped dromedary camel,
but Amil the camel dealer came rolling up to your
camp with a two humped bactrain camel, and none of
your saddles will fit.

It puts a completely different spin on a Monte Carlo
analysis on part tolerances.

No wonder HP only used 1% or better parts.

-Chuck Harris


Ed Breya via groups.io wrote:

Chuck wrote: " What I generally
find is that out of 1000's of 5% resistors, not a single one
was within 1% of its nominal value. But, all were within 5%."

These two-lobed distributions are common. The ones that fell in the middle range near 1% were likely separated out and sold as a better grade part, leaving the rest of the distribution (which should be normal) with a hole in the middle.

Ed






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