The estimable Wolfgang has been doing some interesting measurements on these Chinese zeners, 2DW23x series. Some of them are much quieter even than an LTZ1000!
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 10510hobbs at electrooptical dot net
Bah! What's that got to do with USA politics?
Cool! Does Wolfgang post here? I use the LM399 in a diode laser current source. (I never measured it's noise... good enough for Jan Hall was good enough for me.) Say totally unrelated, but it is about diode lasers.
We've got a summer intern (cute young lady.) She's been aligning diode lasers for me and I said we should have some Friday afternoon fun. An unscripted (obviously) video. At the highest temperature the Rb vapor is optically 'thick' zero transmission at the absorption peaks.
George H. (if you watch till the end you can tell I've been working on my fiendish laugh... :^)
I don't think so. He sure takes a lot of interesting data though--his plots of the islands of stability for diode lasers (noise and line width vs. T and bias current) are really worth study.
The 399 is pretty good considering that it runs at 45C or something. I use the LM329 as my standard voltage reference, and the LT1021 when I need something better. You really have to watch the thermal convection to get good low frequency noise.
Some years back I was building ultrastable diode lasers for a geophysics start-up in Albuquerque NM. It was for a cool gravimeter that had to work 5000 feet down a 2-inch cased drill hole (38 mm maximum package diameter).
The laser eventually had an Allen variance of 1E-10 at 100,000 seconds, which was pretty slick, I thought. I had my own cubicle since I was there one week a month, so I put a nice brass plaque on the wall that said
DC The Final Frontier
Which it really is, if you need stability. You can't filter your way out of trouble down there!
Now you just have to build a Jacob's ladder and grow long hair.
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.. bookmarking his site. (Not to be read in a few hours!) This page?
I'd love a recommendation for a good 650 nm diode laser. (So many fun projects.. if only I could get someone to pay me for them.)
George h.
Grin, summer time all my hair is gone. (And even in the winter it's mighty thin on top.) Here's the cute intern.
She starts physics grad school at U of Chicago in the fall, so a smart cookie too.
GH
Danish butter variety? She looks more Irish. She's certainly better looking than you (or I) either way. ;)
Cheers
Phil Hobbs
He had to do a lot of selection to find the good ones.
ADR421B is pretty good. 0.05% accurate, 1.75 uV p-p in 10 Hz, 3 PPM tempco. I think it's the jfet equivalent of a bandgap.
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
It would be interesting to try to get hold of the Shanghai Factory 17 folks and find out what they did to make the good ones so good. Buried zeners are an old technology, so suddenly getting a 20 dB improvement in the low frequency noise is pretty big news.
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
Phil, I think I understand that, but please correct me if I'm wrong.
At DC you are stuck with 1/f noise, which doesn't filter away. The only way to get better is to make the base-line 1/f smaller. which (from my experience) is piece dependent. Some parts have a better max DC noise rating.
George H.
Am 16.06.2017 um 19:15 schrieb Phil Hobbs:
It does not come as a surprise that "Zeners" that operate well into the avalanche region are not the king of silence. The LTZ1000 is stable, and that's it.
The silence of the lamps:
My personal favourite is the HP/Agilent/Avago/Broadcom? HLMP6000 when I'm only interested in noise. It is a LED, 10 dB _below_ 1nV/rt Hz above 1 KHz. It also de-classes most other LEDs. (Digikey)
<What makes me wonder is the LT6655. It is a band gap, amplifies small differences as such, but keeps up with the good Z-diodes noise wise. OTOH avalanching is also gain in principle.
Obey the data sheet values for the capacitors, more may be less with funny resonance peaks.
With some op amp filtering you can get down to 1 nV/rt Hz @100 Hz without much ado. I used ada4898 since they happened to lay on the table. There may be more stable ones.
<The plots might be better below 50 Hz or so; the noise of my
20 times ADA4898 preamp rises faster than 1/f, much like GR noise because the input coupling capacitor is too small. I have bought some wet tantalums, but the inrush current when connecting might zener the input transistors. With some care they can survive, but sooner or later I'll be absent-minded. That's the reason behind my multi-FET-preamps.cheers, Gerhard
Thanks, that's interesting. I often use a LED plus an emitter follower to m ake a kinda-sorta-TC 1-V reference. It's about 20 dB quieter than a band ga p, though not as stable.
But where references really differ is in their low frequency noise, down be low 1 Hz where you can't filter it out. I'll be interested to see if Wolfga ng's zeners behave well over time and temperature cycling. The brown goo in those die shots makes me a bit dubious about that.
But hey, at least we're talking electronics. :)
Cheers
Phil Hobbs
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