Purpose of precision high-current series regulator's resisto

[Steve Wilson]

Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2020-02-21 07:00, Steve Wilson wrote:
Winfield Hill <winfieldhill@yahoo.com> wrote:

Steve Wilson wrote...

Good News! A trivial change to the circuit ...

What is the change?

See the zip file

I will definitely have to use Gerhard's parallel
LT1028 preamplifier to measure the noise.

Or you could use the 80 pV/rt-Hz circuit in AoE 3.

That is rediculous. It is intended for ribbon microphones, with a
source resistance of 0.2 Ohms. It is also too noisy.

Have you made any measurements yet?

The noise is too low to measure. All the other measurements are
satisfactory.

It's possible
that your SPICE model may be completely wrong, and
there will be no need for any special low-noise preamp to take the
measurement.

After 40 years running SPICE, it is more likely the results are highly
accurate, and offer performance you could never dream of.

Hundreds of thousands of engineers have been taught SPICE in colleges
and universities. How did you miss out?

https://drive.google.com/open?id=162h1_AQ-rCfFou8LaHrKZOpMlGP1PgJP

Steve, did you realize whom you were replying to? Some major fraction
of those hundreds of thousands have been taught out of AoE. I mean, a
healthy ego is one thing....

Many others were taught ot of Terman, Radiation Labs, Radiotron Designer's
Handbook, various engineering magazines, etc.

AOE discusses Intusoft ICAP, but never seems to use it anywhere in the
thousands of opportunities throughout the text. This could have vastly
increased the value of AOE, especially if LTspice were used instead of
ICAP.

In this day and age, lack of skills in LTspice is a career-limiting move.

Those who learned from AOE are at a severe disadvantage.

Cheers

Phil Hobbs

 

[Tom Gardner]

On 21/02/20 20:12, Phil Hobbs wrote:

On 2020-02-21 15:03, Steve Wilson wrote:
Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2020-02-21 07:00, Steve Wilson wrote:
Winfield Hill <winfieldhill@yahoo.com> wrote:

Steve Wilson wrote...

Good News! A trivial change to the circuit ...
   What is the change?

See the zip file
I will definitely have to use Gerhard's parallel
LT1028 preamplifier to measure the noise.
   Or you could use the 80 pV/rt-Hz circuit in AoE 3.

That is rediculous. It is intended for ribbon microphones, with a
source resistance of 0.2 Ohms. It is also too noisy.
   Have you made any measurements yet?

The noise is too low to measure. All the other measurements are
satisfactory.

It's possible
   that your SPICE model may be completely wrong, and
   there will be no need for any special low-noise preamp to take the
   measurement.
After 40 years running SPICE, it is more likely the results are highly
accurate, and offer performance you could never dream of.

Hundreds of thousands of engineers have been taught SPICE in colleges
and universities. How did you miss out?
https://drive.google.com/open?id=162h1_AQ-rCfFou8LaHrKZOpMlGP1PgJP
Steve, did you realize whom you were replying to?  Some major fraction
of those hundreds of thousands have been taught out of AoE.  I mean, a
healthy ego is one thing....
Many others were taught ot of Terman, Radiation Labs, Radiotron Designer's
Handbook, various engineering magazines, etc.

AOE discusses Intusoft ICAP, but never seems to use it anywhere in the
thousands of opportunities throughout the text. This could have vastly
increased the value of AOE, especially if LTspice were used instead of
ICAP.

In this day and age, lack of skills in LTspice is a career-limiting move.

Those who learned from AOE are at a severe disadvantage.


I was looking to give you a way to climb down honourably, but if you want to
double down instead, well, you do that.

Chortle! Best smile of the day.

 

[Steve Wilson]

Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2020-02-21 15:03, Steve Wilson wrote:
Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2020-02-21 07:00, Steve Wilson wrote:
Winfield Hill <winfieldhill@yahoo.com> wrote:

Steve Wilson wrote...

Good News! A trivial change to the circuit ...

What is the change?

See the zip file

I will definitely have to use Gerhard's parallel
LT1028 preamplifier to measure the noise.

Or you could use the 80 pV/rt-Hz circuit in AoE 3.

That is rediculous. It is intended for ribbon microphones, with a
source resistance of 0.2 Ohms. It is also too noisy.

Have you made any measurements yet?

The noise is too low to measure. All the other measurements are
satisfactory.

It's possible
that your SPICE model may be completely wrong, and
there will be no need for any special low-noise preamp to take
the measurement.

After 40 years running SPICE, it is more likely the results are
highly accurate, and offer performance you could never dream of.

Hundreds of thousands of engineers have been taught SPICE in colleges
and universities. How did you miss out?

https://drive.google.com/open?id=162h1_AQ-rCfFou8LaHrKZOpMlGP1PgJP

Steve, did you realize whom you were replying to? Some major fraction
of those hundreds of thousands have been taught out of AoE. I mean, a
healthy ego is one thing....

Many others were taught ot of Terman, Radiation Labs, Radiotron
Designer's Handbook, various engineering magazines, etc.

AOE discusses Intusoft ICAP, but never seems to use it anywhere in the
thousands of opportunities throughout the text. This could have vastly
increased the value of AOE, especially if LTspice were used instead of
ICAP.

In this day and age, lack of skills in LTspice is a career-limiting
move.

Those who learned from AOE are at a severe disadvantage.


I was looking to give you a way to climb down honourably, but if you
want to double down instead, well, you do that.

I truly fail to see what you are driving at. We are talking about careers
and livelihood. You have posted a number of LTspice files. Could you do
this work without LTspice?

Cheers

Phil Hobbs

 

[Phil Hobbs]

On 2020-02-21 17:09, Steve Wilson wrote:

Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2020-02-21 15:03, Steve Wilson wrote:
Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2020-02-21 07:00, Steve Wilson wrote:
Winfield Hill <winfieldhill@yahoo.com> wrote:

Steve Wilson wrote...

Good News! A trivial change to the circuit ...

What is the change?

See the zip file

I will definitely have to use Gerhard's parallel
LT1028 preamplifier to measure the noise.

Or you could use the 80 pV/rt-Hz circuit in AoE 3.

That is rediculous. It is intended for ribbon microphones, with a
source resistance of 0.2 Ohms. It is also too noisy.

Have you made any measurements yet?

The noise is too low to measure. All the other measurements are
satisfactory.

It's possible
that your SPICE model may be completely wrong, and
there will be no need for any special low-noise preamp to take
the measurement.

After 40 years running SPICE, it is more likely the results are
highly accurate, and offer performance you could never dream of.

Hundreds of thousands of engineers have been taught SPICE in colleges
and universities. How did you miss out?

https://drive.google.com/open?id=162h1_AQ-rCfFou8LaHrKZOpMlGP1PgJP

Steve, did you realize whom you were replying to? Some major fraction
of those hundreds of thousands have been taught out of AoE. I mean, a
healthy ego is one thing....

Many others were taught ot of Terman, Radiation Labs, Radiotron
Designer's Handbook, various engineering magazines, etc.

AOE discusses Intusoft ICAP, but never seems to use it anywhere in the
thousands of opportunities throughout the text. This could have vastly
increased the value of AOE, especially if LTspice were used instead of
ICAP.

In this day and age, lack of skills in LTspice is a career-limiting
move.

Those who learned from AOE are at a severe disadvantage.


I was looking to give you a way to climb down honourably, but if you
want to double down instead, well, you do that.

I truly fail to see what you are driving at. We are talking about careers
and livelihood. You have posted a number of LTspice files. Could you do
this work without LTspice?

I do most of my design work without SPICE. Models for board-level
components are mostly horrible, because nobody cares to make them
better, so there's little choice really.

I mostly use SPICE to help prevent blunders, on the theory that my
blunders are unlikely to be the same as the modellers' blunders. For
some limited cases, e.g. slow BJTs, the models are good enough to use
for optimization.

Otherwise it's just a tool for spitballing when I'm too lazy to do the
algebra.

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

 

[Winfield Hill]

Steve Wilson wrote...

Winfield Hill <winfieldhill@yahoo.com> wrote:

Steve Wilson wrote...

Good News! A trivial change to the circuit ...

What is the change?

See the zip file

I'm sorry, which zip file is that? The old one?

I will definitely have to use Gerhard's parallel
LT1028 preamplifier to measure the noise.

Or you could use the 80 pV/rt-Hz circuit in AoE 3.

That is rediculous. It is intended for ribbon microphones,
with a source resistance of 0.2 Ohms. It is also too noisy.

Excuse me, 0.08nV is too noisy? You have a low Zout.

Have you made any measurements yet?

The noise is too low to measure. All the other
measurements are satisfactory.

So, trusting your SPICE numbers, you haven't actually
measured your real circuit on the bench?

It's possible that your SPICE model may be completely
wrong, and there will be no need for any special
low-noise preamp to take the measurement.

You've argued that the high intrinsic noise of the 2n3904
is somehow overcome by placing it in a feedback loop with
a noisier element. No fair adding a massive output cap.

After 40 years running SPICE, it is more likely the results
are highly accurate, and offer performance you could never
dream of.

Hundreds of thousands of engineers have been taught SPICE
in colleges and universities. How did you miss out?

OK, I have been using SPICE for 45 years, on many hundreds
of circuits, and have found hundreds of faulty results. I
mostly use SPICE for careful analysis of a small portion of
a difficult analytically-evaluated circuit, using my own
vetted models. Maybe because I'm evaluating a difficult
aspect, often non-linear, it's easy to see the serious
weaknesses that are there. Many models are very poor.

It's not SPICE that's at fault, per se, but the models. In
these instances I've embarked on a call to urge folks to vet
models on the bench, before trusting a SPICE result. I
haven't seen you do that. Hey, I'm sorry, the bench rules.

Build your circuit, get out your spectrum analyzer, take the
measurements, and report back. SPICE plots don't count.


--
Thanks,
- Win

 

[Tom Gardner]

On 21/02/20 20:12, Phil Hobbs wrote:

On 2020-02-21 15:03, Steve Wilson wrote:
Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2020-02-21 07:00, Steve Wilson wrote:
Winfield Hill <winfieldhill@yahoo.com> wrote:

Steve Wilson wrote...

Good News! A trivial change to the circuit ...
   What is the change?

See the zip file
I will definitely have to use Gerhard's parallel
LT1028 preamplifier to measure the noise.
   Or you could use the 80 pV/rt-Hz circuit in AoE 3.

That is rediculous. It is intended for ribbon microphones, with a
source resistance of 0.2 Ohms. It is also too noisy.
   Have you made any measurements yet?

The noise is too low to measure. All the other measurements are
satisfactory.

It's possible
   that your SPICE model may be completely wrong, and
   there will be no need for any special low-noise preamp to take the
   measurement.
After 40 years running SPICE, it is more likely the results are highly
accurate, and offer performance you could never dream of.

Hundreds of thousands of engineers have been taught SPICE in colleges
and universities. How did you miss out?
https://drive.google.com/open?id=162h1_AQ-rCfFou8LaHrKZOpMlGP1PgJP
Steve, did you realize whom you were replying to?  Some major fraction
of those hundreds of thousands have been taught out of AoE.  I mean, a
healthy ego is one thing....
Many others were taught ot of Terman, Radiation Labs, Radiotron Designer's
Handbook, various engineering magazines, etc.

AOE discusses Intusoft ICAP, but never seems to use it anywhere in the
thousands of opportunities throughout the text. This could have vastly
increased the value of AOE, especially if LTspice were used instead of
ICAP.

In this day and age, lack of skills in LTspice is a career-limiting move.

Those who learned from AOE are at a severe disadvantage.


I was looking to give you a way to climb down honourably, but if you want to
double down instead, well, you do that.

Let's make the "teaching grandmothers to suck eggs"
point extremely explicitly...

In a response to a post from *Win Hill*, Steve Wilson wrote:
"After 40 years running SPICE, it is more likely the
results are highly accurate, and offer performance you
could never dream of.
Hundreds of thousands of engineers have been taught SPICE
in colleges and universities. How did you miss out?"

Mr Wilson might benefit from reading, amongst other things,
https://x.artofelectronics.net/wp-content/uploads/2019/11/2xp4_BJT_amplifier_distortion.pdf

2x.4 BJT Amplifier Distortion: a SPICE Exploration
Our tour of distortion in BJT amplifiers has been fun, and
easy. It let us explore the properties of various configura-
tions, making changes with both little effort and great re-
ward.

But, a warning: SPICE takes its models literally, and
therefore goes seriously off the rails when the models
are inaccurate. We saw this here, with the poor generic
QN5088 model we tried first. Similar problems are found
with MOSFET models, many of which fail completely in
modeling the important “subthreshold region” (§3.1.4A).

*It’s essential to validate your SPICE models with real-world*
*behavior before placing trust in simulations.*

Author? Win Hill, of course.

 

It's not SPICE that's at fault, per se, but the models.  In
 these instances I've embarked on a call to urge folks to vet
 models on the bench, before trusting a SPICE result.  I
 haven't seen you do that.  Hey, I'm sorry, the bench rules.

The ATF38143 pHEMT model I posted awhile back overestimates the 1/f noise by _seventeen_orders_of_magnitude_.

Cheers

Phil Hobbs

 

[Steve Wilson]

Winfield Hill <winfieldhill@yahoo.com> wrote:

Steve Wilson wrote...

Winfield Hill <winfieldhill@yahoo.com> wrote:

Steve Wilson wrote...

Good News! A trivial change to the circuit ...

What is the change?

See the zip file

I'm sorry, which zip file is that? The old one?

Yes. The mission has changed and the file has been updated.

I will definitely have to use Gerhard's parallel
LT1028 preamplifier to measure the noise.

Or you could use the 80 pV/rt-Hz circuit in AoE 3.

That is rediculous. It is intended for ribbon microphones,
with a source resistance of 0.2 Ohms. It is also too noisy.

Excuse me, 0.08nV is too noisy? You have a low Zout.

80pV/root Hz is 2 to 4 times as much as I expect.

Re = 27 / Ie(Ma) = 2.7 Ohms

Have you made any measurements yet?

The noise is too low to measure. All the other
measurements are satisfactory.

So, trusting your SPICE numbers, you haven't actually
measured your real circuit on the bench?

How do you measure between 20pV and 40pV/root Hz?

It's possible that your SPICE model may be completely
wrong, and there will be no need for any special
low-noise preamp to take the measurement.

You've argued that the high intrinsic noise of the 2n3904
is somehow overcome by placing it in a feedback loop with
a noisier element. No fair adding a massive output cap.

I switched to a 2N4401. The LT431 controls the output voltage. There
is a 3-pole lowpass RC filter between the TL431 and the transistor.
The frequency response of the filter is shown in the file.

After 40 years running SPICE, it is more likely the results
are highly accurate, and offer performance you could never
dream of.

I now revise that down to 35 years.

Hundreds of thousands of engineers have been taught SPICE
in colleges and universities. How did you miss out?

OK, I have been using SPICE for 45 years,

Most likely 35 years, same as me.

Intusoft was founded in March 1985:

http://www.intusoft.com/intusoft.php

It is interesting that you barely mention SPICE in AOE2, and waited
for AOE3 to start using it.

on many hundreds
of circuits, and have found hundreds of faulty results. I
mostly use SPICE for careful analysis of a small portion of
a difficult analytically-evaluated circuit, using my own
vetted models. Maybe because I'm evaluating a difficult
aspect, often non-linear, it's easy to see the serious
weaknesses that are there. Many models are very poor.

It's not SPICE that's at fault, per se, but the models. In
these instances I've embarked on a call to urge folks to vet
models on the bench, before trusting a SPICE result. I
haven't seen you do that. Hey, I'm sorry, the bench rules.

The SPICE simulation is essential to tell you if a circuit is worth
spending time on. It is invaluable to help troubleshooting when
something goes wrong on the bench. It allows you to evaluate
different component parameters and see which ones are critical to
obtaining the desired results. It allows you to optimize the circuit
and components for best performance. You can examine the open-loop
response in a feedback circuit and optimize the loop gain, and gain
and phase margin. This can be difficult or impossible to do on the
bench.

It can be difficult and time-consuming to change components on the
bench. You may have to fight noise, poor connections, unwanted
oscillations, test equipment limitations, bad components, and a host
of other problems that interfere with your evaluation. You may lack
the equipment needed to make critical measurements that you can
easily do in simulation.

In fact, in AOE2, you state:

"SPICE (originated by L. W. Nagel) models the operation of your
trial circuit (using a library of sophisticated component models),
predicting the gain, distortion, noise, frequency response, etc. You
can ask it to show you the waveforms (voltage and current) at any
point in the circuit - a computerized oscilloscope! Thus you can
fiddle with your hypothetical circuit, trying speedup capacitors,
exploring component and circuit trade-offs, and so on."

"In fact, good simulators even let you see the effects of component
tolerance, via either conventional worst-case analysis or a more
sophisticated "Monte Carlo" statistical treatment. Some modeling
programs also perform a "sensitivity" analysis, telling you which
components affect performance the most."

LTspice rules.

Build your circuit, get out your spectrum analyzer, take the
measurements, and report back. SPICE plots don't count.

My HP 8566 spectrum analyzer is geared for high microwave
frequencies up to 22GHz. It only has a dynamic range of ~100 dB,
and is unlikely to be able to measure such low noise.

You state:

"SPICE (originated by L. W. Nagel) models the operation of your
trial circuit (using a library of sophisticated component models),
predicting the gain, distortion, NOISE, frequency response, etc."

Thanks,
- Win

 

[Winfield Hill]

Steve Wilson wrote...

Winfield Hill <winfieldhill@yahoo.com> wrote:

Excuse me, 0.08nV is too noisy? You have a low Zout.

80pV/root Hz is 2 to 4 times as much as I expect.
Re = 27 / Ie(Ma) = 2.7 Ohms

The e_n noise in a BJT is not given by r_e, but
instead by the base r'bb, which is much higher.
Read pages 481 to 486, and study Figure 8.12.

We all recognize that your filter can present
a low noise to the base, but your chosen noisy
transistors will determine the output noise.

So, trusting your SPICE numbers, you haven't
actually measured your real circuit on the bench?

How do you measure between 20pV and 40pV/root Hz?

Better go to the bench. You'll get 1.35 nV/rt-Hz
with a 2N3904, with an r'bb of about 110 ohms, and
0.84 nV with a 2N4401, both at 10mA, more or less,
according to our measurements. If you chose some
of the other parts in Table 8.1, you can improve
on that by up to a factor of four to 0.2 nV. Our
80pV preamp can test all of them in your circuit.
With G=50 to 100, you won't need a quiet analyzer.

OK, I have been using SPICE for 45 years,

Most likely 35 years, same as me.
Intusoft was founded in March 1985:

I began using SPICE about 1972, when it was only
a text program. Most engineers prefer to be able
to calculate their circuit parameters, and know
what's going on, and what's responsible for what,
rather simply stab in some component values, and
rely on an overall SPICE output.

It is interesting that you barely mention SPICE
in AOE2, and waited for AOE3 to start using it.

AoE2 was completed in 1988, before manufacturers
began routinely providing SPICE models.

AoE is all about circuit design, and SPICE was not
then and is not now at the center of circuit design.
SPICE was designed specifically for IC design, and
fab houses work very hard to provide accurate models.
As we learned from Jim Thompson, these are usually
proprietary and tightly guarded. Good, but secret.

By contrast, discrete-component manufacturers provide
horrible models. Yes you can often do the bench work,
testing for specific parameters you care about, and
create a good model, but short of that, watch out.
Don't boast about your SPICE circuit's performance,
until you measure it on the bench.


--
Thanks,
- Win

 

[Steve Wilson]

Winfield Hill <winfieldhill@yahoo.com> wrote:

Steve Wilson wrote...

Winfield Hill <winfieldhill@yahoo.com> wrote:

Excuse me, 0.08nV is too noisy? You have a low Zout.

80pV/root Hz is 2 to 4 times as much as I expect.

Re = 27 / Ie(Ma) = 2.7 Ohms

The e_n noise in a BJT is not given by r_e, but
instead by the base r'bb, which is much higher.
Read pages 481 to 486, and study Figure 8.12.

You asked about the output impedance. I was not using that to calculate
noise.

We all recognize that your filter can present
a low noise to the base, but your chosen noisy
transistors will determine the output noise.

As mentioned, I am limited by the transistors that are available in both
LTspice IV and XVII. As mentioned, you are free to select better ones.

The output noise is determined by the 1,000 uF bypass capacitor from the
output to ground, not by the emitter follower. TL431A and TL431B should
make that clear.

IC manufacturers have much better programs for IC design.

LTspice is specifically designed for circuit analysis, and is the preferred
method over pages of equations. How would you analyze my circuits by hand?

The 64,000 members of the LTspice group should make this clear.

https://groups.io/g/LTspice

 

On Sunday, 23 February 2020 03:25:19 UTC, Winfield Hill wrote:

By contrast, discrete-component manufacturers provide
horrible models. Yes you can often do the bench work,
testing for specific parameters you care about, and
create a good model, but short of that, watch out.
Don't boast about your SPICE circuit's performance,
until you measure it on the bench.

I've lost count of how many times Spice has given me kilovolt results for little low voltage circuits with no inductor.


NT

 

[Winfield Hill]

tabbypurr@gmail.com wrote...

On Sunday, 23 February 2020, Winfield Hill wrote:

By contrast, discrete-component manufacturers provide
horrible models. Yes you can often do the bench work,
testing for specific parameters you care about, and
create a good model, but short of that, watch out.
Don't boast about your SPICE circuit's performance,
until you measure it on the bench.

I've lost count of how many times Spice has given me
kilovolt results for little low voltage circuits with
no inductor.

And just now we have a SPICE results thread about a 2GHz
op-amp buffer output stage using a 2N3904 and 2N3906, ha
haw! And this from an article by Dr. Sergio Franco, who
should know better! One can save themselves considerable
embarrassment with a little common-sense analysis, and/or
a bench test, before broadcasting their SPICE results.


--
Thanks,
- Win

 

[Winfield Hill]

Winfield Hill wrote...

tabbypurr@gmail.com wrote...

On Sunday, 23 February 2020, Winfield Hill wrote:

By contrast, discrete-component manufacturers provide
horrible models. Yes you can often do the bench work,
testing for specific parameters you care about, and
create a good model, but short of that, watch out.
Don't boast about your SPICE circuit's performance,
until you measure it on the bench.

I've lost count of how many times Spice has given me
kilovolt results for little low voltage circuits with
no inductor.

And just now we have a SPICE results thread about a 2GHz
op-amp buffer output stage using a 2N3904 and 2N3906, ha
haw! And this from an article by Dr. Sergio Franco, who
should know better! One can save themselves considerable
embarrassment with a little common-sense analysis, and/or
a bench test, before broadcasting their SPICE results.

Paul just returned from a grand Peru vacation, lucky guy,
and has completed measurements on Steve's circuit. Steve
said, "450 pV/root Hz at 10 Hz, and 15 pV/root Hz at 10 kHz
and beyond." But as we expected, given a 2N3904's noise,
e_n was 1.2 to 1.4 nV/rt-Hz. Perhaps Helmut's TL431 model
lacked any noise. Thus his SPICE version of a noisy IC,
was able to quiet a noisy BJT by a factor of nearly 100.
Hah, in reality, an RC filter, plus the BJT follower, can
slightly quiet the noisy TL431, not the other way around.
Again, my advice is to not trust your SPICE model until
it's been bench vetted.


--
Thanks,
- Win