Author Topic: Ultra Precision Reference LTZ1000  (Read 1157120 times)

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Offline Kleinstein

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Re: Ultra Precision Reference LTZ1000
« Reply #2925 on: April 29, 2020, 04:12:19 pm »
The LNA from Pipelie uses an AZ OP (or 2) and thus has essentially no 1/f noise, at least with a short. With a actual voltage there would be noise from the coupling cap if an electrolytic cap is used. I am not sure if the noise show for the battery is more from the battery or possibly from the coupling cap.

The downside of the usual AZ OPs is the limited bandwidth, especially if the first stage is used with a high gain. So 0.1 Hz to 100 kHz could become tricky. However 0.1 Hz to some 10 KHz may be realistic for such a setup without an intentional filter for the upper limit.

Similar one may be able to extend the lower limit a little below 0.1 Hz with a larger capacitor - however things are limited there. It is not just the cross over frequency, but also current noise (which gets visible as 1/f noise with a very larger resistance instead of a larger cap) and also dielectric absorption, so that electrolytic caps need really long settling before using it for slow processes.

For measuring down to really low frequencies the way to go would be using 2 reference and measuring the difference with a DC coupled amplifier, at least for the initial stage, possibly all the way with a DC compensation.
 

Offline branadic

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Re: Ultra Precision Reference LTZ1000
« Reply #2926 on: April 29, 2020, 05:13:51 pm »
Just for inspiration one could have a look at the schematic of SR560:

https://doc.xdevs.com/docs/Standford Research Systems/SR560/Stanford_Research_SR560.pdf

and build something similar to it, maybe with reduced functionality and more modern parts available such as MMBF5103 for the JFET, that was tested to have very low 1/f noise:

http://www.angelfire.com/az3/dimitri/images/AX_Dec2018_pp56-58.pdf

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Offline alanambrose

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Re: Ultra Precision Reference LTZ1000
« Reply #2927 on: May 02, 2020, 06:08:29 pm »
Interesting, following the links I see the NPD5564 pair in the original SR560 is now replaced with a LSK389B pair which is available from Linear (and some other channels) for about $6. Maybe this is drifting off the original subject though...
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Offline MiDi

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Re: Ultra Precision Reference LTZ1000
« Reply #2928 on: May 03, 2020, 01:00:17 pm »
What it would need is an LNA for the complete range 100mHz to 100kHz instead. There are several solutions out there such as DC-1MHz or commercial gear like Stanford Research SR560, but they are expensive. Couldn't find a proper DIY solution for the 100mHz - 100kHz range yet.
I know it gets a bit off topic...

For 0.1Hz to 100kHz Andreas 0.1 to 10Hz LNA could be suitable with some modifications.
With e.g. another LT1037 in second stage and tweaking the lowpass filters to get the cutoff frequency to 100kHz it should do the job and is affordable - I did similar modification a while back for other application.

AN159 10Hz to 100kHz/1MHz (Layout files) might be an option.
Downside is its limitation with low cutoff at 10Hz (1/f corner ~100Hz), so one needs at least second LNA for 0.1 to 10Hz and combine them - not so easy and not so cheap.

If I got it right the SR560 has quite high noise figure at low impedances, it seems better suited for higher source impedances (maybe > 1k \$\Omega\$)
« Last Edit: May 03, 2020, 01:29:25 pm by MiDi »
 
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Offline Andreas

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Re: Ultra Precision Reference LTZ1000
« Reply #2929 on: May 03, 2020, 04:26:23 pm »
Hello,

I initially had a 2nd LT1037 on the output stage.
The result was massive oscillations.
(The reason for the LT1012 in the second stage).
So obviously you will have to do some additional
shielding between stages with 2 * LT1037.

with best regards

Andreas
 
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Offline notfaded1

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Re: Ultra Precision Reference LTZ1000
« Reply #2930 on: May 08, 2020, 04:46:22 pm »
Anyone seen these before?  I bought a couple just to test out and alter a little.  Some of the parts look ok and some could use replacing but you don't see completed boards very often even if missing the LTZ.

Bill
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Offline SilverSolder

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Re: Ultra Precision Reference LTZ1000
« Reply #2931 on: May 09, 2020, 11:52:38 am »
Anyone seen these before?  I bought a couple just to test out and alter a little.  Some of the parts look ok and some could use replacing but you don't see completed boards very often even if missing the LTZ.

Bill

Where did you get them?
 
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Offline BU508A

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Re: Ultra Precision Reference LTZ1000
« Reply #2932 on: May 09, 2020, 12:02:32 pm »
Anyone seen these before?  I bought a couple just to test out and alter a little.  Some of the parts look ok and some could use replacing but you don't see completed boards very often even if missing the LTZ.

Bill

Where did you get them?

I assume, here:

https://www.ebay.com/itm/333584715972
“Chaos is found in greatest abundance wherever order is being sought. It always defeats order, because it is better organized.”            - Terry Pratchett -
 
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Offline picburner

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Re: Ultra Precision Reference LTZ1000
« Reply #2933 on: May 09, 2020, 02:06:59 pm »
You are all really terrible.... I could not resist and I also took a couple :-DD
 
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Offline notfaded1

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Re: Ultra Precision Reference LTZ1000
« Reply #2934 on: May 11, 2020, 04:23:03 pm »
Yep that's where I bought them from @BU508A!  Didn't take long for you guys to buy them all up!   :-DD

I knew this was coming... complete units using new LTZ (I ordered one of these too to try):
https://www.ebay.com/itm/1-Customized-Ultra-Precision-Voltage-Reference-Board-LTZ1000ACH-LTZ1000CH/333594628743

I'm going to add some of my seasoned aged LTZ's to the other bare boards and see if I can improve on the aging time a little.  I've got some PWW to try instead as well.

Bill
« Last Edit: May 11, 2020, 04:42:31 pm by notfaded1 »
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Offline picburner

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Re: Ultra Precision Reference LTZ1000
« Reply #2935 on: May 11, 2020, 05:23:06 pm »
If it can be useful to someone, in the attachment, there is the schematic that the seller has used.
 
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Offline chuckb

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Re: Ultra Precision Reference LTZ1000
« Reply #2936 on: May 14, 2020, 10:53:10 pm »
Noopy provided links to his microscopic views of the LTZ1000 chip here -
https://www.richis-lab.de/REF03.htm

In one of the images you could see light coming from the circular Zener junction. That’s very cool. So, I had to explore that.

I made a little pcb with a tall socket for the LTZ1000. It also had selectable bias currents and operating temperature.

My friend Jim has a great collection of top-of-the-line microscopes. He coupled his new Nikon Z6 to the Nikon Metaphot Metallurgical microscope for the following images.
Thanks Jim!

As you would expect, as the current increased the light increased.
Changing the chip temperature from 50 deg C to 95 deg C at 4ma bias made no noticeable change in the light.

For one image Jim minimized all ambient light so we could capture the full 360 circle of light from the breakdown. Half of the light is hidden behind the trace on the top layer.

Offline CalMachine

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Re: Ultra Precision Reference LTZ1000
« Reply #2937 on: May 14, 2020, 11:03:51 pm »
For one image Jim minimized all ambient light so we could capture the full 360 circle of light from the breakdown. Half of the light is hidden behind the trace on the top layer.


:wtf:


 :scared:
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Offline SilverSolder

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Re: Ultra Precision Reference LTZ1000
« Reply #2938 on: May 14, 2020, 11:11:01 pm »
Interesting how the light appears in "dots" like stars in a nebula.

Guess this is due to imperfections, so some parts of the junction breaks down more than others?

You can imagine how such a process could be electrically noisy...

It would be awesome to record that light with some kind of photodetector and "listen" to it - is the light output noisy like the zener current?

 

Offline Magnificent Bastard

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Re: Ultra Precision Reference LTZ1000
« Reply #2939 on: May 15, 2020, 05:02:11 am »
Interesting how the light appears in "dots" like stars in a nebula.

Guess this is due to imperfections, so some parts of the junction breaks down more than others?

You can imagine how such a process could be electrically noisy...

It would be awesome to record that light with some kind of photodetector and "listen" to it - is the light output noisy like the zener current?

Also, what might prove interesting is to hit the junction with a LASER-- and watch what happens with the 1/f noise and voltage output.  I've been wanting to do this for a long time, but it seems @chuckb beat me to it, and is pretty much ready to do this test!
 
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Offline Kleinstein

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Re: Ultra Precision Reference LTZ1000
« Reply #2940 on: May 15, 2020, 09:21:27 am »
Interesting how the light appears in "dots" like stars in a nebula.

Guess this is due to imperfections, so some parts of the junction breaks down more than others?

You can imagine how such a process could be electrically noisy...

It would be awesome to record that light with some kind of photodetector and "listen" to it - is the light output noisy like the zener current?

I can also imagine the light may show some fluctuations. Changes are these may correlate with noise in the voltage.

I don't think this is a kind of junction break-down. The more likely mechanism is that the zener diode in the avalanche regime produces hot electrons and some of these can get to the surface oxide / interface. Relaxation of the electrons there can happen with light at some suitable states (similar to color centers). 

Normally the idea behind the buried zener is to avoid this effect by keeping the hot electron from reaching the surface. The second point is that they do less harm in the burried zener: this part can still work but is not so visible.
 
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Offline SilverSolder

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Re: Ultra Precision Reference LTZ1000
« Reply #2941 on: May 15, 2020, 11:44:14 am »
Interesting how the light appears in "dots" like stars in a nebula.

Guess this is due to imperfections, so some parts of the junction breaks down more than others?

You can imagine how such a process could be electrically noisy...

It would be awesome to record that light with some kind of photodetector and "listen" to it - is the light output noisy like the zener current?

I can also imagine the light may show some fluctuations. Changes are these may correlate with noise in the voltage.

I don't think this is a kind of junction break-down. The more likely mechanism is that the zener diode in the avalanche regime produces hot electrons and some of these can get to the surface oxide / interface. Relaxation of the electrons there can happen with light at some suitable states (similar to color centers). 

Normally the idea behind the buried zener is to avoid this effect by keeping the hot electron from reaching the surface. The second point is that they do less harm in the burried zener: this part can still work but is not so visible.

If the mechanism is due to electrons relaxing and "going back to bed", perhaps taking a spectrum of the light would show something interesting?  (confirming the material, perhaps, and thereby proving the hypothesis?)
 

Offline Noopy

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Re: Ultra Precision Reference LTZ1000
« Reply #2942 on: May 19, 2020, 05:40:53 am »
Interesting how the light appears in "dots" like stars in a nebula.

Guess this is due to imperfections, so some parts of the junction breaks down more than others?

You can imagine how such a process could be electrically noisy...

It would be awesome to record that light with some kind of photodetector and "listen" to it - is the light output noisy like the zener current?

I can also imagine the light may show some fluctuations. Changes are these may correlate with noise in the voltage.

I don't think this is a kind of junction break-down. The more likely mechanism is that the zener diode in the avalanche regime produces hot electrons and some of these can get to the surface oxide / interface. Relaxation of the electrons there can happen with light at some suitable states (similar to color centers). 

Normally the idea behind the buried zener is to avoid this effect by keeping the hot electron from reaching the surface. The second point is that they do less harm in the burried zener: this part can still work but is not so visible.

Are you sure?
I´m no expert regarding semiconductor physics but in my understanding z-diodes with this voltage rating work at least to some extend in avalanche breakdown.
In avalanche breakdown accelerated electrons hit other electrons setting them free on a not exactly defined energy level. If the energy level is in the range of visible light their recombination can emit visible light.
This recombination will perfectly happen in the junction area. In my view most of the recombination will happen there.
Correct me if I´m wrong.

Offline Kleinstein

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Re: Ultra Precision Reference LTZ1000
« Reply #2943 on: May 19, 2020, 07:03:04 am »
A agree one the way the zener is supposed to work. However I doubt that one would see light from the buried junction. This would be rather deep inside the silicon so only very little of that light can escape. The normal avalanche process  should also not produce light as the energy from the hot electron is used to generate new pairs. The normal recombination in silicon is without any light and if any it would be in the IR range (~ 1 µm). It would be only if a hot electron recombines or excites some defect in some way.

It usually takes some defects so that an indirect semiconductor like silicon can emit light. The logical position would be the surface or just inside the oxide. My estimate is that the way to the surface should be easier for a hot electron than for visible light. This would be different if the light is in the NIR range.
 

Offline Noopy

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Re: Ultra Precision Reference LTZ1000
« Reply #2944 on: May 19, 2020, 10:14:37 am »
However I doubt that one would see light from the buried junction. This would be rather deep inside the silicon so only very little of that light can escape.

I´m not sure about this.
A view days ago I tried to use a big KD501 transistor as a photovoltaic cell.
(https://richis-lab.de/Bipolar02.htm)
Across the base-emitter-junction I got the same current as across the base-collector-junction. It seems there wasn´t significant light reduction.


The normal avalanche process  should also not produce light as the energy from the hot electron is used to generate new pairs. The normal recombination in silicon is without any light and if any it would be in the IR range (~ 1 µm). It would be only if a hot electron recombines or excites some defect in some way.

I agree with you that hot electrons generate new pairs but some of them will recombinate. Otherwise you will get a real breakdown with 0V and destruction of the junction. (I´m not absolutely sure about the last sentence but that would be my interpretation.)
The hot electrons can have a higher energy than you will see while normal current flow in the semiconductor. With "normal" current flow and "normal" recombination you don´t see any light. I agree with that. But in my view there is recombination of hot electrons.


I tried to take a "maximum tilted" picture but you can´t really say where the light is generated:


 
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Offline exe

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Re: Ultra Precision Reference LTZ1000
« Reply #2945 on: May 19, 2020, 11:58:35 am »
How deeply is a buried zener buried? May be the layer above it is thin-enough to be transparrent to the light? May be photons from inner layer somehow re-emmiter from the outer layer? (purelly guessing here, I have zero knowledge about semiconductors)
 

Offline Simon_RL

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Re: Ultra Precision Reference LTZ1000
« Reply #2946 on: May 19, 2020, 12:20:14 pm »
Hi All,
Please don’t laugh at me for this question. I am a newbie to electronics and have developed a strong interest in metrology. I want to build a voltage reference based on the LTZ1000a and unfortunately I haven’t got the knowledge to design my own circuit yet. Basically I need a reference for a few experiments I want to do as part of my learning process. I have been hunting for a good circuit and came across this circuit board on AliExpress. If some one can please provide feedback on this circuit and advise if it is any good it would greatly appreciate. Unfortunately there isn’t a schematic, but there are clear pictures of the board and silk screen. If this is no good and someone could please pint me in the direction of a good design I would really appreciate it.

https://m.aliexpress.com/item/4000615209128.html?spm=a2g0n.wishlist-amp.item.4000615209128&aff_trace_key=&aff_platform=msite&m_page_id=2033amp-vGQRqGHv_FhCn8pzRV1uSQ1589885700140&browser_id=fcbdcf015c134b0ca64ebcab0b0f18c2&is_c=Y

 

Offline BU508A

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Re: Ultra Precision Reference LTZ1000
« Reply #2947 on: May 19, 2020, 01:11:22 pm »
Hi,

welcome to the volt-nuts section.  :)

Hi All,
Please don’t laugh at me for this question. I am a newbie to electronics and have developed a strong interest in metrology. I want to build a voltage reference based on the LTZ1000a and unfortunately I haven’t got the knowledge to design my own circuit yet. Basically I need a reference for a few experiments I want to do as part of my learning process. I have been hunting for a good circuit and came across this circuit board on AliExpress. If some one can please provide feedback on this circuit and advise if it is any good it would greatly appreciate. Unfortunately there isn’t a schematic, but there are clear pictures of the board and silk screen. If this is no good and someone could please pint me in the direction of a good design I would really appreciate it.

https://m.aliexpress.com/item/4000615209128.html?spm=a2g0n.wishlist-amp.item.4000615209128&aff_trace_key=&aff_platform=msite&m_page_id=2033amp-vGQRqGHv_FhCn8pzRV1uSQ1589885700140&browser_id=fcbdcf015c134b0ca64ebcab0b0f18c2&is_c=Y

I strongly recommend to read this thread from the beginning. You'll find a lot of useful information and designs of a good LTZ1000 based reference.
Here are some examples:

LTZ1000 based on the design of Dr. Frank:
https://www.eevblog.com/forum/metrology/ultra-precision-reference-ltz1000/
https://github.com/pepaslabs/dr-frank-ltz1000

TiN's KX-reference:
https://xdevs.com/article/kx-ref/

MX reference from user ManateeMafia
https://www.eevblog.com/forum/metrology/mx-reference/

Lot of work lies in front of you.  :-/O   ;)
« Last Edit: May 19, 2020, 02:25:06 pm by BU508A »
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Offline Simon_RL

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Re: Ultra Precision Reference LTZ1000
« Reply #2948 on: May 19, 2020, 01:58:05 pm »
Hi,

welcome to the volt-nuts section.  :)

Hi All,
Please don’t laugh at me for this question. I am a newbie to electronics and have developed a strong interest in metrology. I want to build a voltage reference based on the LTZ1000a and unfortunately I haven’t got the knowledge to design my own circuit yet. Basically I need a reference for a few experiments I want to do as part of my learning process. I have been hunting for a good circuit and came across this circuit board on AliExpress. If some one can please provide feedback on this circuit and advise if it is any good it would greatly appreciate. Unfortunately there isn’t a schematic, but there are clear pictures of the board and silk screen. If this is no good and someone could please pint me in the direction of a good design I would really appreciate it.

https://m.aliexpress.com/item/4000615209128.html?spm=a2g0n.wishlist-amp.item.4000615209128&aff_trace_key=&aff_platform=msite&m_page_id=2033amp-vGQRqGHv_FhCn8pzRV1uSQ1589885700140&browser_id=fcbdcf015c134b0ca64ebcab0b0f18c2&is_c=Y

I strongly recommend to read this thread from the beginning. You'll find a lot of useful information and designs of a good LTZ1000 based reference.
Here are some examples:

LTZ1000 based on the design of Dr. Frank:
https://www.eevblog.com/forum/metrology/ultra-precision-reference-ltz1000/
https://github.com/pepaslabs/dr-frank-ltz1000

TiN's KX-reference:
https://xdevs.com/article/kx-ref/

MX reference from user ManateeMafia
https://www.eevblog.com/forum/metrology/mx-reference/

Lot of work lies in front of you.  :-/O   ;)

Thanks Heaps BU508A. Very much appreciate your assistance.
« Last Edit: May 19, 2020, 02:03:08 pm by Simon_RL »
 

Online Cerebus

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Re: Ultra Precision Reference LTZ1000
« Reply #2949 on: May 19, 2020, 04:47:43 pm »
However I doubt that one would see light from the buried junction. This would be rather deep inside the silicon so only very little of that light can escape.

I´m not sure about this.
A view days ago I tried to use a big KD501 transistor as a photovoltaic cell.
(https://richis-lab.de/Bipolar02.htm)
Across the base-emitter-junction I got the same current as across the base-collector-junction. It seems there wasn´t significant light reduction.


The normal avalanche process  should also not produce light as the energy from the hot electron is used to generate new pairs. The normal recombination in silicon is without any light and if any it would be in the IR range (~ 1 µm). It would be only if a hot electron recombines or excites some defect in some way.

I agree with you that hot electrons generate new pairs but some of them will recombinate. Otherwise you will get a real breakdown with 0V and destruction of the junction. (I´m not absolutely sure about the last sentence but that would be my interpretation.)
The hot electrons can have a higher energy than you will see while normal current flow in the semiconductor. With "normal" current flow and "normal" recombination you don´t see any light. I agree with that. But in my view there is recombination of hot electrons.


I tried to take a "maximum tilted" picture but you can´t really say where the light is generated:



Several things to note here:

1) If the emission is happening underneath an oxide layer, let us remember that we call the silicon dioxide we encounter on an everyday basis "glass". No problems with light getting through centimetres of glass, let alone microns or 100s of nanometers.

2) The assumption made so far is that silicon is the emission candidate. What if it's the dopant? Several common dopants are very strongly associated with visible emission bands (common: arsenic, phosphorous, less common: gallium). There is, admittedly, very little dopant but we're seeing very little light.

3) The assumption that the material is "too thick" for emissions to make their way out.  Remember that we are in the 100s - 1000s of nanometres territory here. At that scale one's assumptions brought from the normal scale world about opacity are quite likely to be wrong.

This diagram of the structure of the buried Zener from the LM399 might be instructive at this stage. It looks to me like the emission is happening well away from the region where the 'buried' junction action is supposed to be going on, perhaps between the outer ring of P- diffusion and the N- substrate or between the cathode and the surface part of the anode P- diffusion.

[attachimg=1]
Anybody got a syringe I can use to squeeze the magic smoke back into this?
 


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