Zener Vs PN diode difference in forward mode - Page 2

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Re: Zener Vs PN diode difference in forward mode
On 07/13/2017 01:54 PM, John Larkin wrote:
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The UW "geonium" project back in the late '70s, iirc, did much the same  
thing with a single electron.

Cheers

Phil Hobbs

--  
Dr Philip C D Hobbs
Principal Consultant
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Re: Zener Vs PN diode difference in forward mode
"Phil Hobbs"  wrote in message  

On 07/13/2017 01:54 PM, John Larkin wrote:
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The UW "geonium" project back in the late '70s, iirc, did much the same
thing with a single electron.

Cheers

Phil Hobbs

--  
Dr Philip C D Hobbs
Principal Consultant
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Re: Zener Vs PN diode difference in forward mode
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I've been visiting Sandia for the last couple of days. I was talking with a
 low-temperature guy who apparently uses SiGe BJTs at 4K. JFETs deteriorate
 quite badly down there, and other bipolars become open circuits due to car
rier freeze-out, so I was quite surprised to hear that heterojunction bipol
ars keep working.  

Cheers

Phil Hobbs  

Re: Zener Vs PN diode difference in forward mode
On Thursday, July 13, 2017 at 10:15:59 PM UTC-4, snipped-for-privacy@gmail.com wrote:
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r  
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 a low-temperature guy who apparently uses SiGe BJTs at 4K. JFETs deteriora
te quite badly down there, and other bipolars become open circuits due to c
arrier freeze-out, so I was quite surprised to hear that heterojunction bip
olars keep working.  
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Huh,  maybe they would work as low temperature, temperature sensing diodes?
  

George H.

Re: Zener Vs PN diode difference in forward mode
On Thu, 13 Jul 2017 21:13:52 -0400, "Carl Ijames"

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The IonSpec preamp that I saw was uncooled. Here it is:

https://www.dropbox.com/s/4talpxrpoa1555y/DSC03579.JPG?raw=1

It's a pair of fet opamps running as followers. They have no cooling
in vacuum except radiation and run at roughly 120C. Gate current was
so high that they needed 1Meg resistors to ground on the inputs. Shot
and Johnson noise big-time. I figured they gave up at least 30 dB.

Chemists are maybe the worst circuit designers.

I had a pretty promising and suitably weird design but the whole thing
died.


--  

John Larkin         Highland Technology, Inc

lunatic fringe electronics  


Re: Zener Vs PN diode difference in forward mode
"John Larkin"  wrote in message  

On Thu, 13 Jul 2017 21:13:52 -0400, "Carl Ijames"

Quoted text here. Click to load it

The IonSpec preamp that I saw was uncooled. Here it is:

https://www.dropbox.com/s/4talpxrpoa1555y/DSC03579.JPG?raw=1

It's a pair of fet opamps running as followers. They have no cooling
in vacuum except radiation and run at roughly 120C. Gate current was
so high that they needed 1Meg resistors to ground on the inputs. Shot
and Johnson noise big-time. I figured they gave up at least 30 dB.

Chemists are maybe the worst circuit designers.

I had a pretty promising and suitably weird design but the whole thing
died.


--  

John Larkin         Highland Technology, Inc

lunatic fringe electronics
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Re: Zener Vs PN diode difference in forward mode
On Friday, July 14, 2017 at 9:42:32 AM UTC-4, Carl Ijames wrote:
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Re: Cable capacitance, sounds like a job for a driven shield.  
I made a driven shield to look at the Johnson noise (R~1k - 1M)  
of resistors dwon the bottom of a probe.  It didn't make into the  
final instrument, but worked fine.  

George h.  

Re: Zener Vs PN diode difference in forward mode
On Fri, 14 Jul 2017 09:41:54 -0400, "Carl Ijames"

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If it ran cold, nobody told me. There was basically no thermal
conduction from the DIP opamps to the hand-wired ceramic slab. Gain
was unity, so 2nd stage (room temp) noise would overpower even a
zero-noise input stage.

It had terrible birdies from fluorescent light ballasts, AM stations,
everything. The spectrum was a picket fence of spikes above the
already terrible noise floor.

I wonder if an OPA627 will work at cryo temps.


--  

John Larkin         Highland Technology, Inc

lunatic fringe electronics  


Re: Zener Vs PN diode difference in forward mode
On Friday, July 14, 2017 at 4:14:58 PM UTC+2, John Larkin wrote:
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Fat chance. Certain MOSFETs do seem to work in liquid helium

http://www.dtic.mil/dtic/tr/fulltext/u2/a142036.pdf

and I thought that I remembered someone publishing the claim that some RCA pure CMOS op-amp did, but google doesn't throw it up.

--  
Bill Sloman, Sydney

Re: Zener Vs PN diode difference in forward mode
On Friday, July 14, 2017 at 1:39:54 PM UTC-7, snipped-for-privacy@ieee.org wrote:
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Could that be CA3130?    It might have gain, but the currents get all wacky when cold.
Biasing is done with zener and forward diodes and sources are loaded with bipolars.

Possibly there were silicon-on-sapphire specials, NASA would know...

Re: Zener Vs PN diode difference in forward mode

t  
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Sure you're not thinking of the 3100 or 3140? IIRC the 3130 was all-MOS.  (
My dim recollection is that it was all NMOS and not CMOS.)  

Back around 1980, the BiMOS CA3100 had about the best intermod performance  
of any op amp.  

Cheers

Phil Hobbs

Re: Zener Vs PN diode difference in forward mode
On Friday, July 14, 2017 at 6:10:59 PM UTC-7, snipped-for-privacy@gmail.com wrote:

get  
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rains) are loaded  
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 (My dim recollection is that it was all NMOS and not CMOS.)  

I'm looking at the 1976 RCA Integrated Circuits manual.   Same info here:

<https://archive.org/stream/RcaLinearIntegratedCircuitsDataBook1978#page/n2
19/mode/2up>

The outputs of the CA3140 were bipolar, those of the CA3130 were MOS,
but CMOS processes didn't include any resistors back then.   So, the
CA3130 used the same BICMOS process as CA3140, with internal diodes and
NPN drain loads (I just checked: PMOS inputs, the negative terminal is drai
n
loads, not the source - and level translator Q11 is another NPN).

All the bias resistances are presumably base resistors of the bipolar proce
ss.
They'd change value markedly with temperature.

Re: Zener Vs PN diode difference in forward mode
"John Larkin"  wrote in message  

On Fri, 14 Jul 2017 09:41:54 -0400, "Carl Ijames"

Quoted text here. Click to load it

If it ran cold, nobody told me. There was basically no thermal
conduction from the DIP opamps to the hand-wired ceramic slab. Gain
was unity, so 2nd stage (room temp) noise would overpower even a
zero-noise input stage.

It had terrible birdies from fluorescent light ballasts, AM stations,
everything. The spectrum was a picket fence of spikes above the
already terrible noise floor.

I wonder if an OPA627 will work at cryo temps.


--  

John Larkin         Highland Technology, Inc

lunatic fringe electronics
We've slightly trimmed the long signature. Click to see the full one.
Re: Zener Vs PN diode difference in forward mode
On Fri, 14 Jul 2017 17:07:49 -0400, "Carl Ijames"

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My theory is that superconductive magnets are just too expensive for
most analytical science. MRI works because they can charge a thousand
dollars an hour for that.

I was also deeply involved with the Imago atom probe, eventually
acquired by Cameca. I got a lot of zero-value stock.

Science is fun, but not often profitable.


--  

John Larkin         Highland Technology, Inc
picosecond timing   precision measurement  

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Re: Zener Vs PN diode difference in forward mode
On Friday, July 14, 2017 at 11:40:12 PM UTC+2, John Larkin wrote:
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Venture capitalists seem to work on the prionciple that one profitable start-up pays for a lot of duds, with quite a bit left over.

--  
Bill Sloman, Sydney

Re: Zener Vs PN diode difference in forward mode
On Thursday, July 13, 2017 at 1:30:19 PM UTC-4, Carl Ijames wrote:
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Hah!  Thanks Carl.  When I was a postdoc we detected hole CR in GaAs  
quantum wells.  Some of my favorite data... I've kept a copy taped to my  
wall.  Detection was complicated.  We monitored the visible absorption  
spectra as we blasted the sample with an FIR laser.  ~20 cm-1,  500 um.

Bored?  I don't suppose you know anything about atomic physics?  
Farting around at a workshop (for teaching others to use our equipment)
I recreated some work I did ~10 years ago.  Observing the Zeeman splitting  
of a Rubidium absorption line.  And now, when I tried to explain why it  
worked, I just make myself more confused.  It will take me a while to  
organize the data and explain my conundrum.  (So not today.)  
I was going to post on Sci.optics, maybe here too?  

George H.  

Re: Zener Vs PN diode difference in forward mode
"George Herold"  wrote in message  

On Thursday, July 13, 2017 at 1:30:19 PM UTC-4, Carl Ijames wrote:
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Hah!  Thanks Carl.  When I was a postdoc we detected hole CR in GaAs
quantum wells.  Some of my favorite data... I've kept a copy taped to my
wall.  Detection was complicated.  We monitored the visible absorption
spectra as we blasted the sample with an FIR laser.  ~20 cm-1,  500 um.

Bored?  I don't suppose you know anything about atomic physics?
Farting around at a workshop (for teaching others to use our equipment)
I recreated some work I did ~10 years ago.  Observing the Zeeman splitting
of a Rubidium absorption line.  And now, when I tried to explain why it
worked, I just make myself more confused.  It will take me a while to
organize the data and explain my conundrum.  (So not today.)
I was going to post on Sci.optics, maybe here too?

George H.
=======================================================

Sorry, George, can't help with much physics theory.

--  
Regards,
Carl Ijames



Re: Zener Vs PN diode difference in forward mode
On Thu, 13 Jul 2017 12:23:19 -0700 (PDT), George Herold

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Well, I'm bored. I'm tuning the control loop of a DAC-programmable
flyback supply. About 4 minutes per run.  


--  

John Larkin         Highland Technology, Inc

lunatic fringe electronics  


Re: Zener Vs PN diode difference in forward mode
On 12/07/2017 17:06, John Larkin wrote:
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Yes, it does seem that the modelled zener forward drop is fixed, whereas  
a normal diode has a current dependency.  That answers my query, thanks.
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Yes, got that.
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I did try something like that a while back, but couldn't get it stable  
over the temperature range (0 - 180'C with the output transistors at  
around 200'C) so went back to the more standard configuration.

Cheers
--  
Clive

Re: Zener Vs PN diode difference in forward mode
On Thu, 13 Jul 2017 09:22:25 +0100, Clive Arthur

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LT Spice lets you declare a diode to have a constant forward votage
drop, which I guess the zener models have. That can be handy sometimes
but it's not real.



--  

John Larkin         Highland Technology, Inc

lunatic fringe electronics  


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