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From: john larkin <jl@650pot.com>
Newsgroups: sci.electronics.design
Subject: Re: A collection of monographs on high accuracy electronics
Date: Tue, 11 Jun 2024 19:11:51 -0700
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On Wed, 12 Jun 2024 02:50:19 +0100, JM <sunaecoNoSpam@gmail.com>
wrote:

>On Mon, 10 Jun 2024 15:14:40 -0400, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:
>
>>On 2024-06-09 21:43, Phil Hobbs wrote:
>>> On 2024-06-09 20:55, JM wrote:
>>>> On Mon, 10 Jun 2024 00:29:17 -0000 (UTC), Phil Hobbs 
>>>> <pcdhSpamMeSenseless@electrooptical.net> wrote:
>>>>
>>>>> JM <sunaecoNoSpam@gmail.com> wrote:
>>>>>> On Sun, 9 Jun 2024 18:09:24 -0000 (UTC), Phil Hobbs
>>>>>> <pcdhSpamMeSenseless@electrooptical.net> wrote:
>>>>>>
>>>>>>> Jeroen Belleman <jeroen@nospam.please> wrote:
>>>>>>>> On 6/9/24 19:02, ehsjr wrote:
>>>>>>>>> On 6/7/2024 9:14 PM, JM wrote:
>>>>>>>>>> A collection of monographs on high accuracy electronics written 
>>>>>>>>>> by Mr.
>>>>>>>>>> Chris Daykin, following his career predominantly in metrology.
>>>>>>>>>>
>>>>>>>>>> Unfortunately Chris will be unable to complete the unfinished
>>>>>>>>>> monographs (having started end of life care) but there is plenty of
>>>>>>>>>> interest to any analogue engineer.
>>>>>>>>>>
>>>>>>>>>> https://1drv.ms/b/c/1af24d72a509cd48/EZhO_rP5-glDmxtc4ZHycvYBhrsqmyC5tuZjt2NFFsS0gQ?e=Wq2Yj0 
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> Thanks!
>>>>>>>>> Ed
>>>>>>>>
>>>>>>>> I have an issue with his definition of resistor noise power
>>>>>>>> as the product of open-circuit noise voltage and short-circuit
>>>>>>>> current. That makes no sense.
>>>>>>>>
>>>>>>>> There's more than that, probably, but that just jumped out at
>>>>>>>> me.
>>>>>>>>
>>>>>>>> Jeroen Belleman
>>>>>>>>
>>>>>>>
>>>>>>> It?s four times too high, for a start.
>>>>>>>
>>>>>>> Cheers
>>>>>>>
>>>>>>> Phil Hobbs
>>>>>>
>>>>>> "It is shown elsewhere [1] that the noise power is four times the heat
>>>>>> energy which would flow down the conductors
>>>>>> from a warm source resistor to a matching cold resistor."
>>>>>>
>>>>>
>>>>> Which, if true, would solve all our energy problems, except that
>>>>> thermodynamic systems would all be unstable.
>>>>>
>>>>> The thermal noise power produced by a resistor into a matched load is kT
>>>>> per hertz.
>>> 
>>>>
>>>> Sure, which is what he states.  By mentioning a hot and cold resistor 
>>>> he makes it clear that net energy flow is from hot to cold, and that 
>>>> the T refers to the hot source.
>>>>
>>> But apparently he says that it's four times larger than that.
>>> 
>>> I'm not making a microsoft account just to download the PDF, so if you 
>>> want to discuss it further, you could email it to me.
>>> 
>>> Cheers
>>> 
>>> Phil Hobbs
>>> 
>>> 
>>> 
>>Bill was kind enough to send me a copy (thanks again, Bill), and right 
>>there on P. 374, the author says,
>>
>>Pn = 4kTB
>>
>>which is a factor of four too high.
>>
>
>No it isn't. He is calculating the thermal noise power dissipated in an unloaded resistor - something (or at least the related noise voltage) which is actually required in the design process of a transducer/amplifier low S/N system. 

What does that mean? Do unconnected resistors get hot?

A box of resistors could start a fire!