A collection of monographs on high accuracy electronics

Post by JM
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

I've down-loaded it. It reminds me a lot of "Coaxial AC Bridges" by
Kibble and Rayner ISBN 0-85274-389-0, which the author should find
flattering. Kibble is also the Kibble in the Kibble Bridge.

--
Bill Sloman, Sydney
--
This email has been checked for viruses by Norton antivirus software.
www.norton.com

ehsjr

2024-06-09 17:02:17 UTC

Thanks!
Ed

Cursitor Doom

2024-06-09 17:32:41 UTC

Post by JM
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

Post by ehsjr
Thanks!
Ed

Yes, thanks to whoever posted this; very interesting indeed.

Jeroen Belleman

2024-06-09 18:06:10 UTC

Post by JM
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

Phil Hobbs

2024-06-09 18:09:24 UTC

Post by JM
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

--
Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC /
Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics

2024-06-09 23:40:14 UTC

Post by JM
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

Its 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."

Phil Hobbs

2024-06-10 00:29:17 UTC

On Sun, 9 Jun 2024 18:09:24 -0000 (UTC), Phil Hobbs

Post by JM
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

Its 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.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC /
Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics

2024-06-10 00:55:51 UTC

On Sun, 9 Jun 2024 18:09:24 -0000 (UTC), Phil Hobbs

Post by JM
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.
Cheers
Phil Hobbs

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.

john larkin

2024-06-10 01:24:04 UTC

On Sun, 9 Jun 2024 18:09:24 -0000 (UTC), Phil Hobbs

Post by JM
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.
Cheers
Phil Hobbs

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.

If you connect two resistors, the noise voltages create an equivalent
thermal conductivity. I did the math once and I recall that any
reasonable real wires would conduct a lot more heat.

And in real life, capacitance will kill the bandwidth and the heat
transfer.

Phil Hobbs

2024-06-10 01:43:25 UTC

On Sun, 9 Jun 2024 18:09:24 -0000 (UTC), Phil Hobbs

Post by JM
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

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

Phil Hobbs

2024-06-10 19:14:40 UTC

On Mon, 10 Jun 2024 00:29:17 -0000 (UTC), Phil Hobbs

On Sun, 9 Jun 2024 18:09:24 -0000 (UTC), Phil Hobbs

Post by JM
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.

Twenty years ago I posted a brief derivation of the Johnson noise
formula in the thread "thermal noise in resistors - Baffled!", as
follows (with a couple of typos fixed).

Post by Phil Hobbs
One good way of deriving the Johnson noise formula (the sqrt(4kT) thing)
is from classical equipartition of energy. The stored energy in a
capacitor is a single classical degree of freedom, and hence (when
connected to a thermal reservoir, e.g. connected in parallel with a
resistor at temperature T) has a mean energy of kT/2, and since the
energy is CV**2/2, its rms noise voltage is sqrt(kT/C).
The noise bandwidth of a one-pole RC lowpass is (pi/2)*(3 dB BW) =
1/(4RC). Therefore, the noise power spectral density in the flatband is
p_N=(kT/2C)*(4RC) per hertz,
so setting p_N=C(e_N)**2/2, we get
(e_N)**2 = kT*4R
and
e_N = sqrt(4kTR) per root hertz.
This is the same noise that correlated double sampling in CCDs was
designed to deal with. The advantage of this way of looking at it is
that the resistor doesn't have to be linear--CMOS reset switches behave
the same way.

Cheers

Phil Hobbs

Phil Hobbs

2024-06-10 19:20:31 UTC

<snip>

Post by 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.
Twenty years ago I posted a brief derivation of the Johnson noise
formula in the thread "thermal noise in resistors - Baffled!"....

<snip> >

And again the following year, with more discussion...this qualifies as a
well-aged FAQ. ;)

Cheers

Phil Hobbs

Post by Phil Hobbs
Subject: Capacitor-feedback for low noise
Phil Hobbs
Aug 23, 2005, 11:16:25 AM

If you want to calculate the noise you get from an arbitrary circuit,
then you need a model for the noise behavior. The thermal noise of an
impedance Z(f) can be modeled by a Thevenin equivalent circuit, where
the voltage source in series with Z(f) is random with a spectral
density of 4kTRe(Z(f)) V2/Hz. Equivalently, its thermal noise can be
modeled by a Norton equivalent circuit, where the current source in
parallel is random with a spectral density of 4kTRe(1/Z(f)) A2/Hz.

Yes, the physics behind it is summarized in the fluctuation-dissipation
theorem of statistical mechanics, which says that any mechanism that can
dissipate energy has associated fluctuations at finite temperature. If
this weren't so, you could make heat flow spontaneously from cold to hot.
The usual way to derive the Johnson noise formula for a resistor is to
use classical equipartition of energy, which predicts that any single
degree of freedom, e.g. the charge on a capacitor, has an RMS energy of
kT/2. Classical equipartition is a very general consequence of
statistical mechanics, and even in a quantum treatment, it can be shown
to hold for frequencies << kT/h, about 6 THz at room temperature. (The
high-frequency correction is due to the Planck function rolloff.) Since
E=CV**2/2, kT/2 of energy corresponds to voltage Vrms = sqrt(kT/C), and
charge Qrms = CV = sqrt(kTC).
If you have a parallel RC, isolated from the rest of the universe,
this fluctuation must be maintained in equilibrium by the resistor
noise--otherwise, the initial sqrt(kTC) would just discharge through the
resistor. This must be true regardless of the values of R and C.
Therefore, the open-circuit thermal fluctuations of the resistor, in the
bandwidth of the RC, must equal sqrt(kT/C) volts; since the noise BW is
1/(4RC) (noise BW = pi/2* 3 dB BW), the open-circuit resistor noise
voltage density is sqrt[(4RC)*(kT/C)] = sqrt(4kTR), which we all know
and love.
You have to work a little harder to make this demonstration completely
rigorous, e.g. by showing that the fluctuations have to be flat with
frequency, but this is the idea. It can also be shown directly from
statistical mechanics applied to a semiclassical electron gas model of
metallic conduction, but I don't know how that derivation goes.

2024-06-12 01:50:19 UTC

On Mon, 10 Jun 2024 00:29:17 -0000 (UTC), Phil Hobbs

On Sun, 9 Jun 2024 18:09:24 -0000 (UTC), Phil Hobbs

Post by JM
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. No engineer outwith some RF/microwave areas (such are specifing antenna noise temperature) is remotely interested in your definition of noise power as the maximum power which can be extracted from a thermal source (ie by a conjugate source match). The vast majority of engineers (if asked to specify resistor noise power) would present exactly the same equation as Daykin, because they are interested in noise voltage (or current) only.

Post by Phil Hobbs
Twenty years ago I posted a brief derivation of the Johnson noise
formula in the thread "thermal noise in resistors - Baffled!", as
follows (with a couple of typos fixed).

Cheers
Phil Hobbs

john larkin

2024-06-12 02:11:51 UTC

On Mon, 10 Jun 2024 00:29:17 -0000 (UTC), Phil Hobbs

On Sun, 9 Jun 2024 18:09:24 -0000 (UTC), Phil Hobbs

Post by JM
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.

What does that mean? Do unconnected resistors get hot?

A box of resistors could start a fire!

Bill Sloman

2024-06-12 05:00:27 UTC

Post by john larkin

On Mon, 10 Jun 2024 00:29:17 -0000 (UTC), Phil Hobbs

On Sun, 9 Jun 2024 18:09:24 -0000 (UTC), Phil Hobbs

Post by JM
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.

What does that mean? Do unconnected resistors get hot?

No. They certainly don't get warmer than their enviroment, though they
do interact with it.

Post by john larkin
A box of resistors could start a fire!

Obviously not. John Larkin's sense of humour is depressingly pathetic.

--
Bill Sloman, Sydney
--
This email has been checked for viruses by Norton antivirus software.
www.norton.com

2024-06-16 21:20:43 UTC

Post by john larkin

On Mon, 10 Jun 2024 00:29:17 -0000 (UTC), Phil Hobbs

On Sun, 9 Jun 2024 18:09:24 -0000 (UTC), Phil Hobbs

Post by JM
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.

What does that mean? Do unconnected resistors get hot?
A box of resistors could start a fire!

And why would that occur. In thermal equilibrium there is no net transfer of energy either from or to the resistor (when averaged over any time interval of interest appropriate to the bandwidth of current electronic circuits).

The so called resistor thermal "available noise power" KTB implies there is a net power delivery from a source to a load. In the case of maximum transfer the source must dissipate within itself exactly the same as it delivers to the load (due to having the same resistance). However if the so called load is at the same temperature as the source it also delivers KTB to the source and dissipates KTB within its own resistance. Thus there is no net transfer of energy between the two resistors in thermal equilibrium. If one is at a lower temperature than the other there will be a net transfer of energy, but this will be completely dwarfed in any practical system by the energy transferred due to thermal conductivity between the two resistors.

So the power dissipated in a system of two equal value resistors is 4KTB. But this also holds if the two resistors have different values, including the situation where one of the resistors is a short or open circuit (i.e. leaving a single open or short circuit resistor). So it is entirely reasonable to state (as many engineers do) that the thermal noise power of a resistor is 4kTB.

Jeroen Belleman

2024-06-17 10:40:01 UTC

Post by john larkin

On Mon, 10 Jun 2024 00:29:17 -0000 (UTC), Phil Hobbs

On Sun, 9 Jun 2024 18:09:24 -0000 (UTC), Phil Hobbs

Post by JM
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.

What does that mean? Do unconnected resistors get hot?
A box of resistors could start a fire!

And why would that occur. In thermal equilibrium there is no net transfer of energy either from or to the resistor (when averaged over any time interval of interest appropriate to the bandwidth of current electronic circuits).
The so called resistor thermal "available noise power" KTB implies there is a net power delivery from a source to a load. In the case of maximum transfer the source must dissipate within itself exactly the same as it delivers to the load (due to having the same resistance). However if the so called load is at the same temperature as the source it also delivers KTB to the source and dissipates KTB within its own resistance. Thus there is no net transfer of energy between the two resistors in thermal equilibrium. If one is at a lower temperature than the other there will be a net transfer of energy, but this will be completely dwarfed in any practical system by the energy transferred due to thermal conductivity between the two resistors.
So the power dissipated in a system of two equal value resistors is 4KTB. But this also holds if the two resistors have different values, including the situation where one of the resistors is a short or open circuit (i.e. leaving a single open or short circuit resistor). So it is entirely reasonable to state (as many engineers do) that the thermal noise power of a resistor is 4kTB.

I've never seen it stated like that. It doesn't strike me as very
useful to state it like that.

It's very kind of you and of Chris too have made this text available
for all, thank you. However, there is some work to be done to finish
it. For example, in 3-5 5 "Noise matching transformers", it is stated
that the noise resistance goes down with the root of N, the number of
parallel transistors. That is not correct: It goes down with N.

It is true that the noise voltage drops with sqrt(N), but the noise
_current_ rises with sqrt(N). So Rn = Vn*sqrt(1/N)/(In*sqrt(N)) =
Vn/(N*In).

I also have an issue with the use of passive matching transformers
for platinum resistance thermometers. This will obviously not work
near DC.

Jeroen Belleman

Phil Hobbs

2024-06-12 03:12:08 UTC

On Mon, 10 Jun 2024 15:14:40 -0400, Phil Hobbs

On Mon, 10 Jun 2024 00:29:17 -0000 (UTC), Phil Hobbs

On Sun, 9 Jun 2024 18:09:24 -0000 (UTC), Phil Hobbs

Post by JM
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. No engineer outwith some
RF/microwave areas (such are specifing antenna noise temperature) is
remotely interested in your definition of noise power as the maximum
power which can be extracted from a thermal source (ie by a conjugate
source match). The vast majority of engineers (if asked to specify
resistor noise power) would present exactly the same equation as Daykin,
because they are interested in noise voltage (or current) only.

John, I’m sorry that your friend is dying. The fact that it comes to us all
doesn’t make it any easier to take.

I’m reading his stuff, so far with interest, and have zero interest in
rubbishing it, or him.

You said yourself that it was unfinished, which means in part that he
didn’t get the chance to check the final version for errors.

This one error doesn’t mean that it’s worthless, just unfinished.

My first edition contained 107 errors that I know about, which fortunately
I was able to fix in later printings. So believe me, I understand the
problem.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC /
Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics

piglet

2024-06-10 21:12:53 UTC

Post by JM
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

That link doesn’t work for me, is there some other way to access it please?

--
piglet

Edward Rawde

2024-06-12 15:58:53 UTC