Re: gEDA-user: ngspice shot noise

[Al Davis <ad82@xxxxxxxxxxxxxxxx>]

On Sunday 02 October 2005 03:22 pm, 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?

No, and I really believe they all meet all published specs.

Actually, they have relatively few processes from which they 
select lots of device types.  If 2n3904 is the "leftover", that 
would mean it has loose specs, such that they all meet it if 
they work at all.  For example, beta might be between 30 and 
500.  Another device might be 50-150, another 100-200, etc.  
Those are selections.  They will select 100-200 for whatever 
they can sell, then 50-150.  If the process really puts most of 
them in 100-150, they get a good yield and the cheap devices 
are there too.

> > 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'.

This is probably bad design.  Are you getting your transistors 
in those "500 assorted transistors for a dollar" packages?  
Maybe that's the problem.

I doubt if they knowingly sell transistors that have defects 
that cause them to fail prematurely.  The risk of a lawsuit 
would be too high.