[time-nuts] Re: +1/f of transistors

[Alex Pummer]

Noise in Physical Systems
Including 1,f Noise, Biological Systems and Membranes : 10th 
International Conference, August 21-25, 1989, Budapest, Hungary
1990

https://www.google.com/books/edition/Noise_in_Physical_Systems/WyVbzgEACAAJ?hl=en

On 4/9/2022 11:35 AM, Lux, Jim wrote:
> On 4/9/22 10:03 AM, usenet at teply.info wrote:
>> On 09.04.22 15:31, Richard (Rick) Karlquist wrote:
>>>
>>> I am seeing a lot of unsupported "theories" about what should be 
>>> done to make devices with low 1/f noise.  It might be instructive 
>>> for everyone
>>> to read Marv Keshner's PhD dissertation (Stanford) discussing 1/f 
>>> noise.
>>> He looks at all kinds of theories and shows that there is no valid 
>>> cookbook for how to make low 1/f noise devices.  It's the classic
>>> non reproducible process.  I remember an FCS
>>> talk many years ago that NIST guru Fred Walls gave with some theory
>>> on how to get low 1/f noise.  Unlike his other papers which were
>>> well received (and rightly so), this one was rapidly debunked.
>>> I felt bad for Fred, getting out too far over his skills.
>>>
>> Thanks for the hint towards the thesis, I'll ask our library to fetch 
>> a copy.
>>
>> Recently I was discussing some measurement results with my colleagues 
>> as we're trying to come up with a low noise JFET which can 
>> successfully be integrated into a SiGe BiCMOS process, and quite 
>> often we're also struggling to identify why exactly variant A has 
>> significantly lower noise than variant B, or why a new approach does 
>> not improve noise the way it was expected.
>> So from a manufacturing process design point of view, achieving low 
>> 1/f noise indeed is closer to sheer dumb luck than the proverbial 
>> "more art than science" suggest. 
>
>
> This is very, very true. Some manufacturers get very low noise or very 
> low leakage (or both), essentially by being "lucky".  From what I've 
> been told, there's no good models, nor predictions - so people share 
> "lore" of "if you get these 2Nxxxx FETs from the mfr in England, 
> they're really good" until they aren't.   There isn't enough market 
> for these, so I suspect research money to "solve the problem" isn't 
> available.
>
> Like all those microwave MMICs with low noise, they worry about 100 
> MHz and up (if not 1GHz), they certainly don't worry (or control) for 
> noise at 5 MHz, or where the 1/f knee is. So just because you got good 
> results with a batch of them, the next batch might not.  It's not even 
> clear you could come up with a standardized test method, because the 
> noise depends on a lot of other factors (drain current, for instance).
>
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