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Combating Zener Jitter

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  Combating Zener Jitter Chris <cbx@noreply.com> - 2017-05-21 11:06 +0000
    Combating Zener Jitter pcdhobbs@gmail.com - 2017-05-21 04:27 -0700
    Re: Combating Zener Jitter Rafael Deliano <rafael_deliano@arcor.de> - 2017-05-21 16:30 +0200
      Re: Combating Zener Jitter Gerhard Hoffmann <ghf@hoffmann-hochfrequenz.de> - 2017-05-21 17:51 +0200
      Re: Combating Zener Jitter Cursitor Doom <curd@notformail.com> - 2017-05-21 15:55 +0000
        Re: Combating Zener Jitter Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-05-21 09:03 -0700
          Re: Combating Zener Jitter Cursitor Doom <curd@notformail.com> - 2017-05-21 16:29 +0000
            Re: Combating Zener Jitter Winfield Hill <hill@rowland.harvard.edu> - 2017-05-21 17:10 -0700
              Re: Combating Zener Jitter Cursitor Doom <curd@notformail.com> - 2017-05-22 14:01 +0000
              Re: Combating Zener Jitter George Herold <gherold@teachspin.com> - 2017-05-22 07:33 -0700
                Re: Combating Zener Jitter Jon Elson <elson@pico-systems.com> - 2017-05-22 12:02 -0500
                  Re: Combating Zener Jitter George Herold <gherold@teachspin.com> - 2017-05-22 11:29 -0700
                    Re: Combating Zener Jitter Jon Elson <jmelson@wustl.edu> - 2017-05-22 13:48 -0500
                      Re: Combating Zener Jitter George Herold <gherold@teachspin.com> - 2017-05-22 13:28 -0700
                      Re: Combating Zener Jitter George Herold <gherold@teachspin.com> - 2017-05-23 06:28 -0700
                        Re: Combating Zener Jitter Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-05-23 10:38 -0400
                          Re: Combating Zener Jitter George Herold <gherold@teachspin.com> - 2017-05-23 08:11 -0700
                            Re: Combating Zener Jitter Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-05-23 11:36 -0400
                              Re: Combating Zener Jitter George Herold <gherold@teachspin.com> - 2017-05-23 09:28 -0700
                Re: Combating Zener Jitter Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-05-22 15:12 -0400
                  Re: Combating Zener Jitter John Larkin <jjlarkin@highland_snip_technology.com> - 2017-05-22 12:48 -0700
                    Re: Combating Zener Jitter Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-05-22 15:57 -0400
                      Re: Combating Zener Jitter John Larkin <jjlarkin@highlandtechnology.com> - 2017-05-22 21:07 -0700
                        Re: Combating Zener Jitter Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-05-23 10:40 -0400
                          Re: Combating Zener Jitter John Larkin <jjlarkin@highlandtechnology.com> - 2017-05-23 09:06 -0700
                            Re: Combating Zener Jitter Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-05-23 12:12 -0400
                            Re: Combating Zener Jitter Jan Panteltje <pNa0nStpealmtje@yahoo.com> - 2017-05-23 17:46 +0000
                              Re: Combating Zener Jitter John Larkin <jjlarkin@highland_snip_technology.com> - 2017-05-23 11:18 -0700
                                Re: Combating Zener Jitter Jan Panteltje <pNa0nStpealmtje@yahoo.com> - 2017-05-23 19:35 +0000
                                  Re: Combating Zener Jitter John Larkin <jjlarkin@highlandtechnology.com> - 2017-05-23 21:18 -0700
                                    Re: Combating Zener Jitter Jan Panteltje <pNa0nStpealmtje@yahoo.com> - 2017-05-24 16:35 +0000
                                      Re: Combating Zener Jitter John Larkin <jjlarkin@highlandtechnology.com> - 2017-05-25 08:12 -0700
                                        Re: Combating Zener Jitter Jan Panteltje <pNa0nStpealmtje@yahoo.com> - 2017-05-25 15:24 +0000
                                    Re: Combating Zener Jitter Jan Panteltje <pNa0nStpealmtje@yahoo.com> - 2017-05-25 07:40 +0000
                                      Re: Combating Zener Jitter Clifford Heath <no.spam@please.net> - 2017-05-25 17:44 +1000
                                        Re: Combating Zener Jitter Jan Panteltje <pNa0nStpealmtje@yahoo.com> - 2017-05-25 07:52 +0000
                  Re: Combating Zener Jitter George Herold <gherold@teachspin.com> - 2017-05-22 13:33 -0700
              Re: Combating Zener Jitter "Tom Del Rosso" <fizzbintuesday@that-google-mail-domain.com> - 2017-05-27 15:53 -0400
                Re: Combating Zener Jitter Winfield Hill <hill@rowland.harvard.edu> - 2017-05-27 19:15 -0700
    Re: Combating Zener Jitter "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-05-21 11:29 -0500
      Re: Combating Zener Jitter krw@notreal.com - 2017-05-21 16:59 -0400
    Re: Combating Zener Jitter Jon Elson <elson@pico-systems.com> - 2017-05-21 12:07 -0500
    Combating Zener Jitter Anthony Stewart <tony.sunnysky@gmail.com> - 2017-05-29 10:42 -0700
      Re: Combating Zener Jitter Robert Baer <robertbaer@localnet.com> - 2017-05-30 01:14 -0800
    Re: Combating Zener Jitter Anthony Stewart <tony.sunnysky@gmail.com> - 2017-06-06 18:29 -0700

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#461110 — Combating Zener Jitter

Has anyone got any suggestions as to how to best deal with the phenomenon 
of jittering zeners? Preferably without adding excessive complexity to a 
circuit, I mean.

[toc] | [next] | [standalone]

#461111

1. More current. 

2. Switch to an LM329. (Bandgaps are much noisier.)

3. Filtering. 

Cheers

Phil Hobbs

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#461117

> jittering zeners?

Noisy zener diodes ?
Avalanche effect >7V is much noisier than Zener <7V.
http://www.embeddedFORTH.de/temp/Z-noise.pdf
So it may help to replace a 10V zener by two stacked 4,7V.

MfG JRD

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#461124

Am 21.05.2017 um 16:30 schrieb Rafael Deliano:
>> jittering zeners?
> 
> Noisy zener diodes ?
> Avalanche effect >7V is much noisier than Zener <7V.
> http://www.embeddedFORTH.de/temp/Z-noise.pdf
> So it may help to replace a 10V zener by two stacked 4,7V.

It gets even better for smaller voltages.

See
< 
https://www.flickr.com/photos/137684711@N07/24411798996/in/album-72157662535945536/ 
 >

for measurements on the NXP BZX84 - CxVy family.

Gerhard

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#461126

On Sun, 21 May 2017 16:30:26 +0200, Rafael Deliano wrote:

>> jittering zeners?
> 
> Noisy zener diodes ?
> Avalanche effect >7V is much noisier than Zener <7V.
> http://www.embeddedFORTH.de/temp/Z-noise.pdf So it may help to replace a
> 10V zener by two stacked 4,7V.
> 
> MfG JRD

If you spot your zeners jittering, the key thing is to ACT FAST. Grab a 
pair of laundry tongs and place the zeners in a metal container (an old 
2oz St. Julian pipe tobacco tin is ideal) then bury it at midnight on the 
7th day of a waxing moon cycle. It's about the only thing that'll 
permanently kill 'em.
Seriously, there's no such thing as "jittering zeners" AFAIK - it's an 
urban myth.

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#461128

On Sun, 21 May 2017 15:55:13 -0000 (UTC), Cursitor Doom
<curd@notformail.com> wrote:

>On Sun, 21 May 2017 16:30:26 +0200, Rafael Deliano wrote:
>
>>> jittering zeners?
>> 
>> Noisy zener diodes ?
>> Avalanche effect >7V is much noisier than Zener <7V.
>> http://www.embeddedFORTH.de/temp/Z-noise.pdf So it may help to replace a
>> 10V zener by two stacked 4,7V.
>> 
>> MfG JRD
>
>If you spot your zeners jittering, the key thing is to ACT FAST. Grab a 
>pair of laundry tongs and place the zeners in a metal container (an old 
>2oz St. Julian pipe tobacco tin is ideal) then bury it at midnight on the 
>7th day of a waxing moon cycle. It's about the only thing that'll 
>permanently kill 'em.
>Seriously, there's no such thing as "jittering zeners" AFAIK - it's an 
>urban myth.

AKA Flicker Noise
		
                                        ...Jim Thompson
-- 
| James E.Thompson                                 |    mens     |
| Analog Innovations                               |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| STV, Queen Creek, AZ 85142    Skype: skypeanalog |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |

     Thinking outside the box... producing elegant solutions.

"It is not in doing what you like, but in liking what you do that
is the secret of happiness."  -James Barrie

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#461132

On Sun, 21 May 2017 09:03:18 -0700, Jim Thompson wrote:

> AKA Flicker Noise

Yup, pink noise. No jittering/jitterbugging involved. ;)

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#461208

Cursitor Doom wrote...
>
> Jim Thompson wrote:
>
>> AKA Flicker Noise
>
> Yup, pink noise. No jittering/jitterbugging involved. ;)

 Actually, I'd say you're wrong.  The zener noise that we
 see in avalanche mode (greater then 7 volts or so) is due
 to step-wise "microplasma" ns-scale changes in current.
 A decade or so ago we fully discussed it here on s.e.d.,
 complete with measurements, waveforms, detailed physics
 paper references and the works.  Nailed it down.  As it
 happens, the jitterbug analogy isn't so far off.

 This avalanche jitterbug noise source is not available
 in the low-voltage field emission zener operating mode,
 so using two sub-6-volt zeners in series in place of a
 higher-voltage zener, or any of many other good schemes
 would indeed be a good idea.


-- 
 Thanks,
    - Win

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#461248

On Sun, 21 May 2017 17:10:33 -0700, Winfield Hill wrote:

>  This avalanche jitterbug noise source is not available in the
>  low-voltage field emission zener operating mode, so using two
>  sub-6-volt zeners in series in place of a higher-voltage zener, or any
>  of many other good schemes would indeed be a good idea.

Well, I can't argue with *you* of all people! So we have a new term for 
it, then. It's not flicker noise, it's not pink noise, it's "jitterbug 
noise" to coin a phrase. Thanks, Win!

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#461254

On Sunday, May 21, 2017 at 8:10:45 PM UTC-4, Winfield Hill wrote:
> Cursitor Doom wrote...
> >
> > Jim Thompson wrote:
> >
> >> AKA Flicker Noise
> >
> > Yup, pink noise. No jittering/jitterbugging involved. ;)
> 
>  Actually, I'd say you're wrong.  The zener noise that we
>  see in avalanche mode (greater then 7 volts or so) is due
>  to step-wise "microplasma" ns-scale changes in current.
>  A decade or so ago we fully discussed it here on s.e.d.,
>  complete with measurements, waveforms, detailed physics
>  paper references and the works.  Nailed it down.  As it
>  happens, the jitterbug analogy isn't so far off.

Those are some nice threads, I went back and read them a few years 
ago.  Turning lemons into lemonade, a 20V zener baised at ~10uA
makes a nice noise source out to ~100's of kHz. 

I've also been reading Hamamatsu app notes on their Silicon PMT.
Which is really a Si avalanche photodiode in "Geiger-mode" 
(biased above the breakdown voltage.)  Fun stuff.

George H. 
> 
>  This avalanche jitterbug noise source is not available
>  in the low-voltage field emission zener operating mode,
>  so using two sub-6-volt zeners in series in place of a
>  higher-voltage zener, or any of many other good schemes
>  would indeed be a good idea.
> 
> 
> -- 
>  Thanks,
>     - Win

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#461272

George Herold wrote:


> I've also been reading Hamamatsu app notes on their Silicon PMT.
> Which is really a Si avalanche photodiode in "Geiger-mode"
> (biased above the breakdown voltage.)  Fun stuff.
> 
We've been experimenting with Silicon photomultipliers at work, and while 
they have a number of issues, they certainly have huge advantages over 
vacuum photomultipliers.  We've been using the SensL product.

The biggest issue is the breakdown voltage is temperature sensitive, and 
gain varies WIDELY with small changes in temperature or bias voltage.

Jon

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#461281

On Monday, May 22, 2017 at 1:02:20 PM UTC-4, Jon Elson wrote:
> George Herold wrote:
> 
> 
> > I've also been reading Hamamatsu app notes on their Silicon PMT.
> > Which is really a Si avalanche photodiode in "Geiger-mode"
> > (biased above the breakdown voltage.)  Fun stuff.
> > 
> We've been experimenting with Silicon photomultipliers at work, and while 
> they have a number of issues, they certainly have huge advantages over 
> vacuum photomultipliers.  We've been using the SensL product.
> 
> The biggest issue is the breakdown voltage is temperature sensitive, and 
> gain varies WIDELY with small changes in temperature or bias voltage.

Huh, I didn't know about Sens-L.  Thanks!  Hey they make one that is 
sensitive in the NIR! 
http://sensl.com/products/r-series/
I can afford $78 too... if they were in stock. 
(Oh I guess not released yet.  I had to register to look at the data 
sheets.... R-series has ~25% PDE at 800 nm.)  I wonder if they have 
to make them thin, which is why the are not so good in the NIR?  

Do you notice any problem with after pulsing?  It's sorta like dark count,
but a different noise source.    

George H. 
> 
> Jon

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#461283

George Herold wrote:


> 
> Huh, I didn't know about Sens-L.  Thanks!  Hey they make one that is
> sensitive in the NIR!
> http://sensl.com/products/r-series/
> I can afford $78 too... if they were in stock.
> (Oh I guess not released yet.  I had to register to look at the data
> sheets.... R-series has ~25% PDE at 800 nm.)  I wonder if they have
> to make them thin, which is why the are not so good in the NIR?
> 
> Do you notice any problem with after pulsing?  It's sorta like dark count,
> but a different noise source.
We haven't really seen after pulsing in our (very limited so far) testing.
As long as you don't turn the bias up too high, the dark current pulses are 
well below the type of signals we are using, so they just about drop out of 
the system.  That's way better than our results with vacuum PMTs, where the 
dark current is typically enough that it triggers our discriminators.

SensL also has SiPMs that bring out a fast output that is capacitively 
coupled from each micropixel.  You get really good time response from that.
Each micropixel has about an 18 K Ohm quench resistor in series for the 
"slow" output, which we thought would give a horrible time response.  But, 
as we typically fire hundreds of micropixels at a time, it actually is 
nowhere that bad.

Yeah, they have stupid rules about registering to read advertising copy, I 
have NO IDEA why outfits do this.  SiPMs are not exactly the newest concept 
out there.

Jon

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#461292

On Monday, May 22, 2017 at 2:46:27 PM UTC-4, Jon Elson wrote:
> George Herold wrote:
> 
> 
> > 
> > Huh, I didn't know about Sens-L.  Thanks!  Hey they make one that is
> > sensitive in the NIR!
> > http://sensl.com/products/r-series/
> > I can afford $78 too... if they were in stock.
> > (Oh I guess not released yet.  I had to register to look at the data
> > sheets.... R-series has ~25% PDE at 800 nm.)  I wonder if they have
> > to make them thin, which is why the are not so good in the NIR?
> > 
> > Do you notice any problem with after pulsing?  It's sorta like dark count,
> > but a different noise source.
> We haven't really seen after pulsing in our (very limited so far) testing.
> As long as you don't turn the bias up too high, the dark current pulses are 
> well below the type of signals we are using, so they just about drop out of 
> the system.  That's way better than our results with vacuum PMTs, where the 
> dark current is typically enough that it triggers our discriminators.

Huh, that's strange.  I thought these Si-pmt's had more dark count.  
If you keep the bias low enough it may just be an avalanche PD, and 
not one in geiger mode. (?)  I recall a SPAD paper that said the dark count
goes as the square the the excess voltage (IIRC), where excess voltage is 
voltage above the threshold for geiger mode.  
> 
> SensL also has SiPMs that bring out a fast output that is capacitively 
> coupled from each micropixel.  You get really good time response from that.
> Each micropixel has about an 18 K Ohm quench resistor in series for the 
> "slow" output, which we thought would give a horrible time response.  But, 
> as we typically fire hundreds of micropixels at a time, it actually is 
> nowhere that bad.
> 
> Yeah, they have stupid rules about registering to read advertising copy, I 
> have NO IDEA why outfits do this.  SiPMs are not exactly the newest concept 
> out there.
No worries, I was interested enough to register.
(What's one more piece of spam in my inbox...)  

George H. 
> 
> Jon

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#461346

On Monday, May 22, 2017 at 2:46:27 PM UTC-4, Jon Elson wrote:
> George Herold wrote:
> 
> 
> > 
> > Huh, I didn't know about Sens-L.  Thanks!  Hey they make one that is
> > sensitive in the NIR!
> > http://sensl.com/products/r-series/
> > I can afford $78 too... if they were in stock.
> > (Oh I guess not released yet.  I had to register to look at the data
> > sheets.... R-series has ~25% PDE at 800 nm.)  I wonder if they have
> > to make them thin, which is why the are not so good in the NIR?
> > 
> > Do you notice any problem with after pulsing?  It's sorta like dark count,
> > but a different noise source.
> We haven't really seen after pulsing in our (very limited so far) testing.
> As long as you don't turn the bias up too high, the dark current pulses are 
> well below the type of signals we are using, so they just about drop out of 
> the system.  That's way better than our results with vacuum PMTs, where the 
> dark current is typically enough that it triggers our discriminators.

Hi Jon, what sort of dark current do you see?  
The dark current between individual PMT's can change by more than an
order of magnitude.  
Do you have an adjustable or fixed threshold level? 
(With fixed you can change the pmt bias voltage to change the 
pulse height.)  

But maybe you've moved on too... just thinking last night.

George h. 
> 
> SensL also has SiPMs that bring out a fast output that is capacitively 
> coupled from each micropixel.  You get really good time response from that.
> Each micropixel has about an 18 K Ohm quench resistor in series for the 
> "slow" output, which we thought would give a horrible time response.  But, 
> as we typically fire hundreds of micropixels at a time, it actually is 
> nowhere that bad.
> 
> Yeah, they have stupid rules about registering to read advertising copy, I 
> have NO IDEA why outfits do this.  SiPMs are not exactly the newest concept 
> out there.
> 
> Jon

[toc] | [prev] | [next] | [standalone]

#461355

On 05/23/2017 09:28 AM, George Herold wrote:
> On Monday, May 22, 2017 at 2:46:27 PM UTC-4, Jon Elson wrote:
>> George Herold wrote:
>>
>>
>>>
>>> Huh, I didn't know about Sens-L.  Thanks!  Hey they make one that is
>>> sensitive in the NIR!
>>> http://sensl.com/products/r-series/
>>> I can afford $78 too... if they were in stock.
>>> (Oh I guess not released yet.  I had to register to look at the data
>>> sheets.... R-series has ~25% PDE at 800 nm.)  I wonder if they have
>>> to make them thin, which is why the are not so good in the NIR?
>>>
>>> Do you notice any problem with after pulsing?  It's sorta like dark count,
>>> but a different noise source.
>> We haven't really seen after pulsing in our (very limited so far) testing.
>> As long as you don't turn the bias up too high, the dark current pulses are 
>> well below the type of signals we are using, so they just about drop out of 
>> the system.  That's way better than our results with vacuum PMTs, where the 
>> dark current is typically enough that it triggers our discriminators.
> 
> Hi Jon, what sort of dark current do you see?  
> The dark current between individual PMT's can change by more than an
> order of magnitude.  
> Do you have an adjustable or fixed threshold level? 
> (With fixed you can change the pmt bias voltage to change the 
> pulse height.)  
> 
> But maybe you've moved on too... just thinking last night.
> 
> George h. 

If any APD seems to have lower input-referred dark current than any PMT,
something is badly wrong.

APDs are a good six orders of magnitude worse on an area basis.

Cheers

Phil Hobbs

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

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net

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#461359

On Tuesday, May 23, 2017 at 10:38:14 AM UTC-4, Phil Hobbs wrote:
> On 05/23/2017 09:28 AM, George Herold wrote:
> > On Monday, May 22, 2017 at 2:46:27 PM UTC-4, Jon Elson wrote:
> >> George Herold wrote:
> >>
> >>
> >>>
> >>> Huh, I didn't know about Sens-L.  Thanks!  Hey they make one that is
> >>> sensitive in the NIR!
> >>> http://sensl.com/products/r-series/
> >>> I can afford $78 too... if they were in stock.
> >>> (Oh I guess not released yet.  I had to register to look at the data
> >>> sheets.... R-series has ~25% PDE at 800 nm.)  I wonder if they have
> >>> to make them thin, which is why the are not so good in the NIR?
> >>>
> >>> Do you notice any problem with after pulsing?  It's sorta like dark count,
> >>> but a different noise source.
> >> We haven't really seen after pulsing in our (very limited so far) testing.
> >> As long as you don't turn the bias up too high, the dark current pulses are 
> >> well below the type of signals we are using, so they just about drop out of 
> >> the system.  That's way better than our results with vacuum PMTs, where the 
> >> dark current is typically enough that it triggers our discriminators.
> > 
> > Hi Jon, what sort of dark current do you see?  
> > The dark current between individual PMT's can change by more than an
> > order of magnitude.  
> > Do you have an adjustable or fixed threshold level? 
> > (With fixed you can change the pmt bias voltage to change the 
> > pulse height.)  
> > 
> > But maybe you've moved on too... just thinking last night.
> > 
> > George h. 
> 
> If any APD seems to have lower input-referred dark current than any PMT,
> something is badly wrong.
Right, maybe a noisy pmt power supply?  
Or a crappy preamp.  I redesigned a pmt preamp.  A colleague used 
an Amptek A111.  It was not the right choice.  (spendy too.)

George H. 
> 
> APDs are a good six orders of magnitude worse on an area basis.
> 
> Cheers
> 
> Phil Hobbs
> 
> -- 
> Dr Philip C D Hobbs
> Principal Consultant
> ElectroOptical Innovations LLC
> Optics, Electro-optics, Photonics, Analog Electronics
> 
> 160 North State Road #203
> Briarcliff Manor NY 10510
> 
> hobbs at electrooptical dot net
> http://electrooptical.net

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#461364

On 05/23/2017 11:11 AM, George Herold wrote:
> On Tuesday, May 23, 2017 at 10:38:14 AM UTC-4, Phil Hobbs wrote:
>> On 05/23/2017 09:28 AM, George Herold wrote:
>>> On Monday, May 22, 2017 at 2:46:27 PM UTC-4, Jon Elson wrote:
>>>> George Herold wrote:
>>>>
>>>>
>>>>>
>>>>> Huh, I didn't know about Sens-L.  Thanks!  Hey they make one that is
>>>>> sensitive in the NIR!
>>>>> http://sensl.com/products/r-series/
>>>>> I can afford $78 too... if they were in stock.
>>>>> (Oh I guess not released yet.  I had to register to look at the data
>>>>> sheets.... R-series has ~25% PDE at 800 nm.)  I wonder if they have
>>>>> to make them thin, which is why the are not so good in the NIR?
>>>>>
>>>>> Do you notice any problem with after pulsing?  It's sorta like dark count,
>>>>> but a different noise source.
>>>> We haven't really seen after pulsing in our (very limited so far) testing.
>>>> As long as you don't turn the bias up too high, the dark current pulses are 
>>>> well below the type of signals we are using, so they just about drop out of 
>>>> the system.  That's way better than our results with vacuum PMTs, where the 
>>>> dark current is typically enough that it triggers our discriminators.
>>>
>>> Hi Jon, what sort of dark current do you see?  
>>> The dark current between individual PMT's can change by more than an
>>> order of magnitude.  
>>> Do you have an adjustable or fixed threshold level? 
>>> (With fixed you can change the pmt bias voltage to change the 
>>> pulse height.)  
>>>
>>> But maybe you've moved on too... just thinking last night.
>>>
>>> George h. 
>>
>> If any APD seems to have lower input-referred dark current than any PMT,
>> something is badly wrong.
> Right, maybe a noisy pmt power supply?  

Or ridiculously high gain, or a gassy tube, or an IR PMT running
uncooled, or a radium-dial clock on the bench, or horrible capacitive
pickup due to being unshielded, or badly wrong dynode voltages causing
arcing, or boatloads of stray light, or....  Something, anyway.

> Or a crappy preamp.  I redesigned a pmt preamp.  A colleague used 
> an Amptek A111.  It was not the right choice.  (spendy too.)

PMTs don't actually need super nice front ends.  Having a nearly
noiseless 100-120 dB of current gain can easily make a 50-ohm amp
competitive--a million electrons arriving in 20 ns is 8 uA, so a 50 ohm
amp with a 300K noise temperature and 25 MHz BW (20 ns equivalent
width) would have a SNR of

SNR = 10 log[(8uA)**2 * 50R]/(-203.8dBW + 74 dB) = 45 dB

for a single-photon pulse. Minus 3 dB or something due to smearing out
the pulse by sqrt(2).  Still a really easy job for a 50-ohm amp.

Cheers

Phil Hobbs

> 
> George H. 
>>
>> APDs are a good six orders of magnitude worse on an area basis.
>>
>> Cheers
>>
>> Phil Hobbs
>>
>> -- 
>> Dr Philip C D Hobbs
>> Principal Consultant
>> ElectroOptical Innovations LLC
>> Optics, Electro-optics, Photonics, Analog Electronics
>>
>> 160 North State Road #203
>> Briarcliff Manor NY 10510
>>
>> hobbs at electrooptical dot net
>> http://electrooptical.net
> 


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

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net

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#461378

On Tuesday, May 23, 2017 at 11:37:07 AM UTC-4, Phil Hobbs wrote:
> On 05/23/2017 11:11 AM, George Herold wrote:
> > On Tuesday, May 23, 2017 at 10:38:14 AM UTC-4, Phil Hobbs wrote:
> >> On 05/23/2017 09:28 AM, George Herold wrote:
> >>> On Monday, May 22, 2017 at 2:46:27 PM UTC-4, Jon Elson wrote:
> >>>> George Herold wrote:
> >>>>
> >>>>
> >>>>>
> >>>>> Huh, I didn't know about Sens-L.  Thanks!  Hey they make one that is
> >>>>> sensitive in the NIR!
> >>>>> http://sensl.com/products/r-series/
> >>>>> I can afford $78 too... if they were in stock.
> >>>>> (Oh I guess not released yet.  I had to register to look at the data
> >>>>> sheets.... R-series has ~25% PDE at 800 nm.)  I wonder if they have
> >>>>> to make them thin, which is why the are not so good in the NIR?
> >>>>>
> >>>>> Do you notice any problem with after pulsing?  It's sorta like dark count,
> >>>>> but a different noise source.
> >>>> We haven't really seen after pulsing in our (very limited so far) testing.
> >>>> As long as you don't turn the bias up too high, the dark current pulses are 
> >>>> well below the type of signals we are using, so they just about drop out of 
> >>>> the system.  That's way better than our results with vacuum PMTs, where the 
> >>>> dark current is typically enough that it triggers our discriminators.
> >>>
> >>> Hi Jon, what sort of dark current do you see?  
> >>> The dark current between individual PMT's can change by more than an
> >>> order of magnitude.  
> >>> Do you have an adjustable or fixed threshold level? 
> >>> (With fixed you can change the pmt bias voltage to change the 
> >>> pulse height.)  
> >>>
> >>> But maybe you've moved on too... just thinking last night.
> >>>
> >>> George h. 
> >>
> >> If any APD seems to have lower input-referred dark current than any PMT,
> >> something is badly wrong.
> > Right, maybe a noisy pmt power supply?  
> 
> Or ridiculously high gain, or a gassy tube, or an IR PMT running
> uncooled, or a radium-dial clock on the bench, or horrible capacitive
> pickup due to being unshielded, or badly wrong dynode voltages causing
> arcing, or boatloads of stray light, or....  Something, anyway.
> 
> > Or a crappy preamp.  I redesigned a pmt preamp.  A colleague used 
> > an Amptek A111.  It was not the right choice.  (spendy too.)
> 
> PMTs don't actually need super nice front ends.  Having a nearly
> noiseless 100-120 dB of current gain can easily make a 50-ohm amp
> competitive--a million electrons arriving in 20 ns is 8 uA, so a 50 ohm
> amp with a 300K noise temperature and 25 MHz BW (20 ns equivalent
> width) would have a SNR of
> 
> SNR = 10 log[(8uA)**2 * 50R]/(-203.8dBW + 74 dB) = 45 dB
> 
> for a single-photon pulse. Minus 3 dB or something due to smearing out
> the pulse by sqrt(2).  Still a really easy job for a 50-ohm amp.

Right, I didn't say it was hard.  (after all, *I* got it to work first try.)

GH
> 
> Cheers
> 
> Phil Hobbs
> 
> > 
> > George H. 
> >>
> >> APDs are a good six orders of magnitude worse on an area basis.
> >>
> >> Cheers
> >>
> >> Phil Hobbs
> >>
> >> -- 
> >> Dr Philip C D Hobbs
> >> Principal Consultant
> >> ElectroOptical Innovations LLC
> >> Optics, Electro-optics, Photonics, Analog Electronics
> >>
> >> 160 North State Road #203
> >> Briarcliff Manor NY 10510
> >>
> >> hobbs at electrooptical dot net
> >> http://electrooptical.net
> > 
> 
> 
> -- 
> Dr Philip C D Hobbs
> Principal Consultant
> ElectroOptical Innovations LLC
> Optics, Electro-optics, Photonics, Analog Electronics
> 
> 160 North State Road #203
> Briarcliff Manor NY 10510
> 
> hobbs at electrooptical dot net
> http://electrooptical.net

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#461285

On 05/22/2017 10:33 AM, George Herold wrote:
> On Sunday, May 21, 2017 at 8:10:45 PM UTC-4, Winfield Hill wrote:
>> Cursitor Doom wrote...
>>>
>>> Jim Thompson wrote:
>>>
>>>> AKA Flicker Noise
>>>
>>> Yup, pink noise. No jittering/jitterbugging involved. ;)
>>
>>  Actually, I'd say you're wrong.  The zener noise that we
>>  see in avalanche mode (greater then 7 volts or so) is due
>>  to step-wise "microplasma" ns-scale changes in current.
>>  A decade or so ago we fully discussed it here on s.e.d.,
>>  complete with measurements, waveforms, detailed physics
>>  paper references and the works.  Nailed it down.  As it
>>  happens, the jitterbug analogy isn't so far off.
> 
> Those are some nice threads, I went back and read them a few years 
> ago.  Turning lemons into lemonade, a 20V zener baised at ~10uA
> makes a nice noise source out to ~100's of kHz. 
> 
> I've also been reading Hamamatsu app notes on their Silicon PMT.
> Which is really a Si avalanche photodiode in "Geiger-mode" 
> (biased above the breakdown voltage.)  Fun stuff.
> 
> George H. 

I'm in conversation with a big biosci company about cost-reducing their
detection subsystems, so this has come up a lot lately.  "Si PMTs" are
basically an array of APDs wired in parallel and run in Geiger mode.
The idea is that having multiple pixels allows you to extend Geiger mode
to pulses containing more photons without losing resolution.

AFAIK the biggest ones are about 120x120 pixels.  Trouble is, even when
uniformly illuminated they start to become nonlinear at depressingly low
photon numbers--the linearity error is 10% once 10% of the pixels have
fired, because only 90% are available.

You can apply a correction for this that might work adequately up to
about 25%, but it starts to run out of gas pretty fast compared with a
real PMT.  Their dynamic range requirements were much too large for this
to work for them.

Also the dark counts are ridiculously worse--more than 10**6 times worse
on an area basis.

The real advantage of MPPCs is that you can do thresholding, which helps
reject single-pixel events at the expense of sensitivity.  That reduces
the effective dark count rate by a lot.

Cheers

Phil Hobbs


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

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net

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