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

[Joseph Gwinn]

On Sat, 09 Apr 2022 20:55:53 -0400, time-nuts-request at lists.febo.com 
wrote:
time-nuts Digest, Vol 216, Issue 16

Answers interspersed below.  

> ------------------------------

Message: 2
Date: Sat, 9 Apr 2022 13:38:58 +0200
From: "usenet at teply.info" <usenet at teply.info>
Subject: [time-nuts] Re: +1/f of transistors
To: time-nuts at lists.febo.com

On 07.04.22 22:58, Joseph Gwinn wrote:

>>>> 
What those folk are currently using for capacitance multipliers and
the like (where low 1/f noise is also essential) are SiGe transistors
like the following:  BFP640H (Infineon), BFP780, SAV541
(MiniCircuits), and 2S2114K (NPN, beta 1200) for high current
>>> 
and 2SD2704 from ROHM, even more beta
>> 

Interesting.  I would not have thought of this one.  It's big and
slow, and made from modern very clean silicon, so it could have low
1/f noise.  Its transition frequency (*= gain-BW product?) is 35 MHz,
so it ought to work on switcher noise.

>>> Those SiGe transistors have wonderful low Rbb of just a few Ohms,
which results in nice low voltage noise, but some have 1/f corners
of 50 MHz or more; that kills my application completely.
>> 
While these chips are small, they are made from very clean material,
so one wonders why so high. The circuit should be physically designed
as if it were to be handling GHz signals, because it could be
oscillating far above the capability of available instruments to
detect.

> IF the base and emitter doping would be done through ion implantation, 
this can create a lot of defects, which act as recombination centres. 
....

I always wondered about such details.  I gather from this and some 
following posts that it is known how to greatly reduce 1/f noise in 
transistors, but it's a nuisance, and so isn't generally done.  But 
what saves us is if the intended purpose of the transistor type 
requires the cleanest of material and the best processes to yield low 
defects such as trapping centers.  Such as the above-mentioned 
difficulties in getting the in-situ doping correct in SiGe 
transistors.

I wonder if there would be a market for making selected standard 
transistors using a really good modern process, one that is otherwise 
overkill.  The wafer need not be all of one kind of transistor.


> ------------------------------

Message: 4
Date: Sat, 9 Apr 2022 06:31:27 -0700
From: "Richard (Rick) Karlquist" <richard at karlquist.com>
Subject: [time-nuts] Re: +1/f of transistors
To: Discussion of precise time and frequency measurement
	<time-nuts at lists.febo.com>,        "usenet at teply.info"
	<usenet at teply.info>

I am seeing a lot of unsupported "theories" about what should be done 
to make devices with low 1/f noise.  ....

Hmm.  What do you make of Handel's quantum theory of flicker noise?  
Van Der Ziel did support it, saying that while he (Ziel) didn't know 
if the derivation of the theory was correct, he _did_ know that this 
theory fit all the data he had collected over the decades, and 
nothing else fit nearly so well.  Meaning that this kind of fit may 
be a big clue, even if the present theory isn't airtight.  This was 
forty years ago.  I'd guess that some people may be using Handel's 
theory simply because of the agreement with all that data.  If I 
recall, he did predict that 1/f noise is inversely proportional to 
active volume, which is certainly as long observed - thus the 
paralleling of multiple smaller transistors or other devices.

.<https://en.wikipedia.org/wiki/Quantum_1/f_noise>


> ------------------------------


MMessage: 10
Date: Sat, 9 Apr 2022 11:35:06 -0700
From: "Lux, Jim" <jim at luxfamily.com>
Subject: [time-nuts] Re: +1/f of transistors
To: time-nuts at lists.febo.com
Message-ID: <4a430e68-7444-2021-2814-cf182d2dda11 at luxfamily.com>
Content-Type: text/plain; charset=UTF-8; format=flowed

On 4/9/22 10:03 AM, usenet at teply.info wrote:

> 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).

I bet (hope?) it isn't quite that bad.  

But the fact that one cannot test and sort for 10-Hz flicker noise in 
three milliseconds would suffice.

> ------------------------------

Message: 11
Date: Sat, 9 Apr 2022 12:28:28 -0700
From: Alex Pummer <alex at pcscons.com>
Subject: [time-nuts] Re: +1/f of transistors
To: time-nuts at lists.febo.com
Message-ID: <6a425b3c-717a-01a1-889b-c43650db9c63 at pcscons.com>
Content-Type: text/plain; charset=UTF-8; format=flowed

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>

Another good source.  But at 700 pages, could take a while.  Were 
there any revelations?

Joe Gwinn