Re: gEDA-user: ngspice shot noise

[Gene Heskett <gene.heskett@xxxxxxxxxxx>]

On Thursday 29 September 2005 14:07, Karel Kulhavy wrote:
>> >>thermal noise due to base resistance were your limiting factor.
>> >
>> >Because only RF transistor has transition frequency of 25GHz.
>>
>> Fight, but you said you were going to use this where a 2N3904 would
>> have enough speed so why do you need a 25 GHz Ft?  Also you said you
>> were going to run at a current level low enough to drop the Ft down to
>> 300 MHz.
>
>Because 2N3904 will have enough speed at 5mA collector current which
>generates huge shot noise. 25GHz Ft will have 300MHz speed at I don't
>know 1uA of current which will generate substantially less noise?
>
>CL<

An old C.E.T. speaking here, with 55 years experience.

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.
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'.

-- 
Cheers, Gene
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