Combating Zener Jitter

1. More current.

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

2. Filtering.

Cheers

Phil Hobbs

Noisy zener diodes ? Avalanche effect >7V is much noisier than Zener

Am 21.05.2017 um 16:30 schrieb Rafael Deliano:

It gets even better for smaller voltages.

See <

>

for measurements on the NXP BZX84 - CxVy family.

Gerhard

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      | 
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Take away their coffee.

Tim

-- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website:

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

Best solution is not to use them in noise-sensitive applications. The best I've seen, so far, is the LM4140. If there isn't a version with the voltage you need, use an AD706, the only op-amp I've found with guaranteed 1/f speced out to 1/1000 Hz.

Jon

I was going to suggest Valium.

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

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!

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.

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

Huh, I didn't know about Sens-L. Thanks! Hey they make one that is sensitive in the NIR!

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.

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

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

If your customer is gigantic enough, maybe Hamamatsu would sell them the cute little MEMS PMTs.

--

John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com

Wouldn't that be nice! Of course the designer has probably died of old age by now....

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

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.

No worries, I was interested enough to register. (What's one more piece of spam in my inbox...)

George H.