Author Topic: Ultra Precision Reference LTZ1000  (Read 959039 times)

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Online SilverSolder

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Re: Ultra Precision Reference LTZ1000
« Reply #2950 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 #2951 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 #2952 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 #2953 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 #2954 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 #2955 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

 

Online BU508A

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Re: Ultra Precision Reference LTZ1000
« Reply #2956 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 »
“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 Simon_RL

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Re: Ultra Precision Reference LTZ1000
« Reply #2957 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 #2958 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.


Anybody got a syringe I can use to squeeze the magic smoke back into this?
 

Offline Noopy

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Re: Ultra Precision Reference LTZ1000
« Reply #2959 on: May 19, 2020, 05:17:43 pm »
...

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.

(Attachment Link)


I agree with you in most points except the last one. Be aware that the round thing in the middle of the LTZ1000 is a buried zener and a transistor.

I took also a picture of the transistor working in breakdown:



=> The z-diode has to be around the transistor.

Online Cerebus

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Re: Ultra Precision Reference LTZ1000
« Reply #2960 on: May 19, 2020, 10:47:51 pm »

I agree with you in most points except the last one. Be aware that the round thing in the middle of the LTZ1000 is a buried zener and a transistor.

I took also a picture of the traor working in breakdown:



=> The z-diode has to be around the transistor.

Even with my very limited understanding of silicon fabrication I don't believe that is right. The circular structure fits every diagram of a buried zener that I've ever seen, and the structures further out (outside the central region) look much more like what I understand a bipolar transistor to look like on a die. There are more than the two shown in the schematic (I can see 4 things that definitely look like transistors, perhaps even eight), but it is quite common for multiple transistors to be paralleled 'on chip' into a single transistor to allow for thermal balancing, dealing with thermal gradients and the like - exactly what one might expect on a chip like the LTZ1000.

I'd be deeply grateful if someone who is actually properly qualified at decoding dies shots would produce an annotated version of one of the many LTZ1000 die shots kicking about marking out the actual transistors, their CBE connections and so on.
Anybody got a syringe I can use to squeeze the magic smoke back into this?
 

Offline splin

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Re: Ultra Precision Reference LTZ1000
« Reply #2961 on: May 19, 2020, 11:33:05 pm »
Can you buy 'reasonably priced' germanium microscope optics to allow an IR camera to be used to show where currents flow and the current densities?
 

Offline Noopy

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Re: Ultra Precision Reference LTZ1000
« Reply #2962 on: May 20, 2020, 07:57:41 am »
Even with my very limited understanding of silicon fabrication I don't believe that is right. The circular structure fits every diagram of a buried zener that I've ever seen, and the structures further out (outside the central region) look much more like what I understand a bipolar transistor to look like on a die. There are more than the two shown in the schematic (I can see 4 things that definitely look like transistors, perhaps even eight), but it is quite common for multiple transistors to be paralleled 'on chip' into a single transistor to allow for thermal balancing, dealing with thermal gradients and the like - exactly what one might expect on a chip like the LTZ1000.

I'd be deeply grateful if someone who is actually properly qualified at decoding dies shots would produce an annotated version of one of the many LTZ1000 die shots kicking about marking out the actual transistors, their CBE connections and so on.

Well looking in detail at my own assumptions I have to admit you are right. But I´m right, too.  ;D





The z-diode is designed as descriped in the LM399 diagram. It is connected with the red metal (cathode) and the black metal (anode).
The transistor Q1 is already there with it´s emitter connected to the blue metal in the center. The base is a part of the z-diode (red). The collector is connected from the edge (white).

So there is a transistor which is surrounded by the z-diode but it´s already in the z-diode structure.

The "avalanche lights" confirm this: You can see the base-emitter-junction on the edge of the middle circle whereas the z-diode-junction is buried under the surrounding ring.

Q2 consists of four transistors surrounding the z-diode and Q1 (grey, yellow, blue).

 :-+


Can you buy 'reasonably priced' germanium microscope optics to allow an IR camera to be used to show where currents flow and the current densities?

I´m afraid such an optic is unaffordable...  :'(

Online magic

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Re: Ultra Precision Reference LTZ1000
« Reply #2963 on: May 20, 2020, 09:48:39 am »
Our friends at Foveon produced a marketing graphic which illustrates light penetration through silicon.


It is my vague recollection that the depth of base and emitter diffusions in a typical "medium voltage" monolithic bipolar process is a few microns, emitters of course being shallower than bases.

I'd be deeply grateful if someone who is actually properly qualified at decoding dies shots would produce an annotated version of one of the many LTZ1000 die shots kicking about marking out the actual transistors, their CBE connections and so on.
There was some speculation and links to semi-helpful sources in Noopy's original LTZ teardown thread. As an improperly qualified hobbyist I think I had figured it out at one point. See if my old posts make any sense to you.

edit
Another source, this time with concrete numbers. If I read it right, 36% of red/orange light (as seen on Noopy's photos) should be able to pass through a few microns of silicon.
https://www.pveducation.org/pvcdrom/materials/optical-properties-of-silicon
« Last Edit: May 20, 2020, 12:58:16 pm by magic »
 
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Online Cerebus

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Re: Ultra Precision Reference LTZ1000
« Reply #2964 on: May 20, 2020, 02:43:28 pm »



The z-diode is designed as descriped in the LM399 diagram. It is connected with the red metal (cathode) and the black metal (anode).
The transistor Q1 is already there with it´s emitter connected to the blue metal in the center. The base is a part of the z-diode (red). The collector is connected from the edge (white).

So there is a transistor which is surrounded by the z-diode but it´s already in the z-diode structure.

The "avalanche lights" confirm this: You can see the base-emitter-junction on the edge of the middle circle whereas the z-diode-junction is buried under the surrounding ring.

Q2 consists of four transistors surrounding the z-diode and Q1 (grey, yellow, blue).

 :-+

Looking at a larger picture with the bonding wires I can see:

Red connects to pin 3 - Zener cathode
Black connects to pin 4 - Q1 base/Zener anode
White connects to pin 5 - Q1 collector
Yellow connects to pin 6 - Q2 base
Blue connects to pin 7 - Q1/Q2 emitters
Grey connects to pin 8 - Q2 collector

So, the Black trace connects to the Q1 base/Zener anode and Red is the Zener cathode, not as stated "The base is a part of the z-diode (red)." So the base connection is the outer circle.

My head now officially hurts from sitting here for 15 minutes trying to imagine exactly what the 3D structure of Q1/the Zener actually looks like and I'm still not there. Fortunately shopping calls so I've an excuse to give up, at least for the time being.
Anybody got a syringe I can use to squeeze the magic smoke back into this?
 

Offline Noopy

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Re: Ultra Precision Reference LTZ1000
« Reply #2965 on: May 20, 2020, 05:30:54 pm »
Looking at a larger picture with the bonding wires I can see:

Red connects to pin 3 - Zener cathode
Black connects to pin 4 - Q1 base/Zener anode
White connects to pin 5 - Q1 collector
Yellow connects to pin 6 - Q2 base
Blue connects to pin 7 - Q1/Q2 emitters
Grey connects to pin 8 - Q2 collector

So, the Black trace connects to the Q1 base/Zener anode and Red is the Zener cathode, not as stated "The base is a part of the z-diode (red)." So the base connection is the outer circle.

My head now officially hurts from sitting here for 15 minutes trying to imagine exactly what the 3D structure of Q1/the Zener actually looks like and I'm still not there. Fortunately shopping calls so I've an excuse to give up, at least for the time being.

Damn! I´m wrong. You are right.  :-+
You got me on a wrong track.
If I´m not wrong again my first statement was actually right: In the middle circle there is a zener with a transistor inside it. zener and Q1 share some parts but there is more inside the LTZ1000 than you can see in the datasheet of the LM399.


Online magic

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Re: Ultra Precision Reference LTZ1000
« Reply #2966 on: May 23, 2020, 09:07:21 am »
I took another look at that thing and this is my best guess of what the internal structure might be, assuming they use the standard noncomplementary bipolar process.



D1 uses the buried zener construction described in Linear AN82, but with a central hole to contain Q1. The anode consists of two P diffusions of different depth, breadth and strenght. The cathode is a strong and shallow N diffusion which fully covers the area of highest P concentration where breakdown voltage is lowest and actual breakdown will occur. This active part of the junction is located a few microns beneath the surface.

Q1 is a standard vertical NPN (top to bottom: EBC). Base is the same silicon as D1 anode, providing the necessary connection which is nowhere to be found on the surface. There is a thin, cross-shaped disturbance visible on the surface which is probably caused by a buried layer diffusion below. Such diffusion could connect Q1 collector to the four contacts surrounding the reference diode structure which are all wired to pin 5. Alternatively, D1 anode could have no hole and Q1 collector would be the N silicon which surrounds D1 anode, but then Q1 would have considerable base width and probably poor beta.

It is known that D1 anode is connected to the substrate and, according to designer Carl Nelson, there exists a subsurface Kelvin connection to the bottom of D1. I presume it all means that the anode is not isolated from the substrate by the buried layer, except for the aforementioned four thin lines. Between the lines, the buried layer is empty and the anode connects with the substrate.

A second similar ring of deep P diffusion is located outside, to isolate D1/Q1 from other transistors. This ring also is penetrated by the buried layer Q1 collector links. On its surface there is a metal connection to pin 4.

Q2 consists of four standard vertical NPNs placed around the reference structure and wired in parallel.

Comments, questions and arguments are welcome :popcorn:
 
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Offline Noopy

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Re: Ultra Precision Reference LTZ1000
« Reply #2967 on: May 23, 2020, 03:33:00 pm »
I took another look at that thing and this is my best guess of what the internal structure might be, assuming they use the standard noncomplementary bipolar process.

(Attachment Link)

D1 uses the buried zener construction described in Linear AN82, but with a central hole to contain Q1. The anode consists of two P diffusions of different depth, breadth and strenght. The cathode is a strong and shallow N diffusion which fully covers the area of highest P concentration where breakdown voltage is lowest and actual breakdown will occur. This active part of the junction is located a few microns beneath the surface.

Q1 is a standard vertical NPN (top to bottom: EBC). Base is the same silicon as D1 anode, providing the necessary connection which is nowhere to be found on the surface. There is a thin, cross-shaped disturbance visible on the surface which is probably caused by a buried layer diffusion below. Such diffusion could connect Q1 collector to the four contacts surrounding the reference diode structure which are all wired to pin 5. Alternatively, D1 anode could have no hole and Q1 collector would be the N silicon which surrounds D1 anode, but then Q1 would have considerable base width and probably poor beta.

It is known that D1 anode is connected to the substrate and, according to designer Carl Nelson, there exists a subsurface Kelvin connection to the bottom of D1. I presume it all means that the anode is not isolated from the substrate by the buried layer, except for the aforementioned four thin lines. Between the lines, the buried layer is empty and the anode connects with the substrate.

A second similar ring of deep P diffusion is located outside, to isolate D1/Q1 from other transistors. This ring also is penetrated by the buried layer Q1 collector links. On its surface there is a metal connection to pin 4.

Q2 consists of four standard vertical NPNs placed around the reference structure and wired in parallel.

Comments, questions and arguments are welcome :popcorn:

Chapeau! Good explanation, good picture, very nice!  :-+ :-+ :-+
Sound reasonable!  :-+

...how did you paint this?



Online magic

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Re: Ultra Precision Reference LTZ1000
« Reply #2968 on: May 23, 2020, 06:01:06 pm »
...how did you paint this?
A few circles, rectangles and 45° rotations to get one quarter of the top surface, then mirror to get a full half, then perspective transformation. All functions available in gimp, I'm sure other advanced image editors like Photoshop could do it too.
The cross section is just a few ellipses drawn on a new layer which restricted them to the bottom half of the frame. That's cheating; frankly, the base diffusion should have a flat bottom over most of its area ::)
It actually is pretty simple in retrospect but I spent an hour learning how to operate that crazy software.
 

Online SilverSolder

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Re: Ultra Precision Reference LTZ1000
« Reply #2969 on: May 23, 2020, 06:06:40 pm »
A vector drawing application like Adobe Illustrator, or Inkscape in the open source world, would be perfect for that kind of work!

Photoshop will work, but it has to be flogged to go there, kicking, screaming, and protesting the whole way...  (It has only rudimentary vector drawing capabilities).  I have never tried the Gimp but I imagine it doesn't major on vector drawing eiter.   Photoshop is to Illustrator what Gimp is to Inkscape, I believe.
 

Online magic

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Re: Ultra Precision Reference LTZ1000
« Reply #2970 on: May 23, 2020, 07:08:57 pm »
I used zero vector graphics capabilities and drew it like in Microsoft Paint :D

Yes, I know. But vector graphics would be yet another even more specialized software to learn. Raster editors are more versatile; everything I did today I will probably want to do to a photograph or some bitmap graphic downloaded from the Internet another day. In the past I used Gimp to alter schematics in PNG format, try that with a vector editor :)
 

Offline exe

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Re: Ultra Precision Reference LTZ1000
« Reply #2971 on: May 24, 2020, 11:21:34 am »
wow, I was under impression that the picture was made in a chip design CAD.
 

Online SilverSolder

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Re: Ultra Precision Reference LTZ1000
« Reply #2972 on: May 24, 2020, 11:26:08 am »
I used zero vector graphics capabilities and drew it like in Microsoft Paint :D

Yes, I know. But vector graphics would be yet another even more specialized software to learn. Raster editors are more versatile; everything I did today I will probably want to do to a photograph or some bitmap graphic downloaded from the Internet another day. In the past I used Gimp to alter schematics in PNG format, try that with a vector editor :)

I hear you.  These applications have big learning curves.  But there are really only those two fundamental types...    if we ignore 3D for now!  :D
 

Offline martinr33

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Re: Ultra Precision Reference LTZ1000
« Reply #2973 on: May 24, 2020, 01:20:52 pm »
Here's a paper describing light emission from a silicon avalanche diode. Fantastic to see those pictures.

https://aip.scitation.org/doi/10.1063/1.4931056
 
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Online magic

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Re: Ultra Precision Reference LTZ1000
« Reply #2974 on: May 25, 2020, 09:46:45 am »
wow, I was under impression that the picture was made in a chip design CAD.
No. I'm not a professional designer, just spent too much time staring at analog ICs :P

The drawing is to be taken with a grain of salt. It may be wrong altogether and various minor details are certainly wrong.

It's completely not to scale, in real world the deep diffusions are almost half-spherical because the dopant doesn't care which direction to diffuse, the concentration of dopant steadily decreases as it diffuses further away from the point of application which I didn't bother trying to show, the shallow diffusions ought to have flat bottoms because the "point" of application is not a single point or line but a wide 2D area, possibly other things...
 
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