Low drift, low noise, fast opamp

Hello John,

Ouch, that hurt.

--
Regards, Joerg

http://www.analogconsultants.com

Hello John,

Well, since jitter seems to be an important parameter in marketing your products lower noise could still yield some upsides. In my case there also is plenty of light but it's the subtle variations in it that I have to detect down to the noise level. The noise coming from the LD is another matter, of course, and that I still have to find out. There would be no point in having a super duper receiver when the source has the noise figure of Niagara Falls.

Sometimes you just have to decouple it to muffle the Rf/Ci pole unless the diode is only a pF or so with plenty of bias. I was told to provide for diode brands that can only take 5V bias and that didn't cause happiness here.

So far the common emitter stages I did behaved themselves. Except for logistical things way down the line like obsoleted RF transistors. The best hotrods came from Motorola. Then they spun it off and that was the end of many of these.

The weirdest ones are spec sheets for catheters: Length in cm, acceptable guide wire dimension in mils, shaft diameter in French (some kind af ancient medical unit). All in the same drawing.

I remember bread and butter pudding from England. Yummy. They pronounced it something like bre-a-bu-uh pudding.

--
Regards, Joerg

http://www.analogconsultants.com

that.

I prefer single ended if noise is an issue, you only have the noise from one junction instead of 2 as in an op amp. For the HF stage the stability of junction bias voltage isnt going to be an issue.

DG mosfet is my usual choice. However 1ma is a fair bit and should give you a reasonable voltage at 100mhz accros say 10pf, wich compared to even a modest op amp input voltage noise this should give you considerable SNR. probably enough for 10bit ADC at a rough gues.

The usual high bandwidth cmos op amp TCA circuit with addition of a cmos zero drift op amp keeping the (-) input at 0v by adjusting the (+) input ref point might be worth looking at.

Colin =^.^=

What sort of laser are you using? What wavelength? Some of the VCSELS are horrendously noisy.

5v is nasty. More volts reduces C and increases the field strength, sweeps the holes out better, and makes them faster.

NEC makes wonderful fast transistors still. I wonder if a cascode of a pin diode and a phemt would work. The phemts are very stable. But you'd have to pre-bias enough current to keep the common-gate input impedance down, then you'd have to subtract that back out somewhere downstream.

My recipe winds up in a single-serving ramekin with a layer of smooth custard on the bottom and bread and berries floating on top. It ain't bad.

John

[...]

Hope you have greener fingers than me. After much faffing about, achieved near stability but it required a closed loop gain of 500. (yes, that low Vos comes in useful:) Maybe AD's demo' board is stable. I certainly haven't spotted the 8099 displaying any real world indications of stability or phase margin. john

--
Posted via a free Usenet account from http://www.teranews.com

Hello John,

It is the Sumitomo SLT5411, a DFB module. The datasheets on LDs are IMHO notoriously skimpy. Could write to them but in my experience that usually doesn't yield much in additional info.

In our case 100MHz would be plenty so we'll probably be ok with it.

Yes, NEC is a great source. But for a prototype run their parts can be as hard to get as Infineon's.

Sounds delicious. Yesterday night I wouldn't have been able to eat one more bite. Why am I now hungry again?

This time we were at former neighbors. The husband was taken by a brain tumor about the same time Jim's son passed away. The first Thanksgiving without a loved one is really hard on a family.

--
Regards, Joerg

http://www.analogconsultants.com

Hello Colin,

I grew up with this discrete stuff so it is familiar but for breadboarding it's often a bear.

What we are measuring isn't the absolute signal which will be huge in this case. We are after subtle differences in that signal, and a whole lot more than 60dB. Basically we need to squeeze out all we can get. Of course, I don't yet know what amount of noise will originate at the DFB module. It wouldn't make sense to build a super-quiet front end and then the laser swamps it with its own noise.

Don't need a servo loop anymore because I've split the DC/LF path from the RF path. The DC path is pretty much licked.

--
Regards, Joerg

http://www.analogconsultants.com

Hello John,

Oops. Thanks for the hint. IIUC it seems that the 8099 was a hot potato in terms of getting it stable. In that case I'd rather go discrete.

--
Regards, Joerg

http://www.analogconsultants.com

I think the dfb's are a lot better, less gross mode jumps and such.

Hey, you can get the Sumitomos on ebay for $500!

Did you see Phil's papers on differential detection?

The idea of looking for very small variations in fiber-coupled light levels is terrifying to me. Fiber levels jump all over the place with the slightest change of temperature or positioning or cosmological constant. As Phil says, everything is an etalon.

Mouser seems able to get me NEC parts, even the ones not in their catalog. Or just call CEL... they're usually very helpful.

I noticed that too. Just had bread pudding and pecan pie and Peet's coffee for breakfast, whipped cream on all of the above, and now Mo is making noises about turkey and mashed potatoes revisited.

John

Hello John,

We did, sometimes for a lot less :-)

Yes, Phil's site is absolutely great. In this case it's not just amplitude but also the spectral width that matters since we are riding a slope and measuring amplitude there. But I won't complain, if stuff was always easy the world wouldn't need consultants.

It is indeed a bit terrifying. If there only was some more quantitative data, plus graphs and stuff. Comparing the datasheet of any old 25c opamp with that of a $500 laser diode it is disappointing when you hold those few sheets in hand. All but page 3 and half of page 4 contain ordering information and mechanical data. A pittance.

Mouser is a good store. Often their prices were lower than Digikey. The only thing I don't like about them is the puny search engine.

When I moved to the US I was amazed at the sizes of Turkeys on Thanksgiving. I don't know why, but yesterday they cooked a 26lbs bird for six people. The biggest one I ever did was 18lbs because I can't get a larger one into the Weber barbie. So, we all have lots of meat left over for the next days. But we need a breather so tonight I am going to cook burgers. All from scratch, none of that pre-pressed stuff. But I'll be out in the cold winds for a while to barbeque them. Beer in hand...

--
Regards, Joerg

http://www.analogconsultants.com

achieved

Vos

Donkey's years ago, Ferranti had a 8 pin DIP, 800pV/rootHz, x1000, -3db at

15MHz chip. Modern theorists would have us believe it should have been impossibly unstable but it worked nicely with no problems, even when plugged into a waffle style breadboard. 20 years later and we're offered similar or lesser spec' devices that will (maybe?) only 'work' when integrated into a setup consisting of transmission lines, ground planes and 0403 components. Seems now we have better technologies but inferior designers. Or maybe line managers no longer have the technical nous to call a halt to poor quality work. My trust has been shot. Now have to waste valuable customer time in just confirming that selected new I.Cs are (or are not), actually capable of doing what they say on tin. john

--
Posted via a free Usenet account from http://www.teranews.com

Hello John,

That's why I do a lot of things with discretes. Much less can go wrong if the highest level of integration is a 3-pin SOT23 ;-)

But AD is 'sposed to be the Mercedes-Benz of semiconductor companies...

That is indeed occurring more frequently. In the first ten years of my career I had only one instance where a chip wouldn't perform and the vendor was a quite arrogant about that (was supposed to be operated between 4.75V and 5.25V but wouldn't perform unless fed 6V). In the last

10 years I had half a dozen cases. The last one (a TPS regulator) remains unexplained. Instead of throwing it on PSPICE they kept asking for more and more data from us. So I dumped it.

--
Regards, Joerg

http://www.analogconsultants.com

[snip]

John who?

Hey Joerg, When are you going to join the rest of us in the 21st Century and provide a proper attribution at the beginning of your replies ?:-)

Newsreader setup too complicated for you ?:-)

...Jim Thompson

-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | |

| 1962 | I love to cook with wine. Sometimes I even put it in the food.

Hello Jim,

This ok, then?

Most of my neighbors think I haven't made it into the 21st century. My car doesn't have central lock, no electric windows, we're still gitten the tee-vee from the erriall. Oh, just came back from re-loading the wood stove...

An engineer at a client last week mentioned a movie we've got to see. Only on DVD, told him we don't have a player for that. His reply: "Why am I not surprised?". (I am the guy there who sometimes still designs with, gasp, trainsisters)

--
Regards, Joerg

http://www.analogconsultants.com

Put the date and time in there and you've got it ;-)

I've even got remote locks on the pick-up truck... added after-market.

Not on the truck, but on the Q45... I like 'em, they're convenient.

The Q45 even remembers my seat settings... and the seats feature heating and cooling for my tender tush ;-)

I'm behind a mountain, so radio and TV aren't very good via the aerial.

I've got two fireplaces... the one outside has a draft fan on it so they wind down the hill doesn't blow smoke in your face ;-)

Tape sucks, gets noisy after not too many plays. In my ~300 movie library I'm down to maybe 10 tapes... I've bought DVD replacements for all my favorites.

"trainsisters"? N, HO, or O gauge ?:-)

I still do discrete designs. My Atlanta project is all off-the-shelf stuff.

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
I love to cook with wine.      Sometimes I even put it in the food.

Oh boy. I guess inserting a different reply header means writing some code into some *.js file that is in who-knows-which directory. And me not good programmer. I'll look at the Mozilla site whether there is a shortcut to do that.

Any fellow readers know how to add date&time to the reply header in Mozilla Suite?

Until one croaks, like on my wife's car. Bzzzz - brrrrroar - clunckkk. She had to come straight back home because she didn't want to leave the car in front of the market with one window down.

They aren't good over here either. But what's there to see anyhow?

Storage is worse. After 10-15 years they show the first V-sync gaps. Then again I had numerous CDs delaminate, bloom and whatnot. So I guess that DVDs won't be much better.

We had Fleischmann. I was totally stunned when I visited my girlfriend (now my wife...) for the first time and she had a whole room in her house dedicated to a model railroad. Before moving across the pond we gave it away.

I thought it's all chips now. What's Atlanta about? Got to fly there some more?

--
Regards, Joerg

http://www.analogconsultants.com

Same here. I 'sposed t'same until I sampled their AD9833 DDS. "Sine, Triangle, Square" they say. Great stuff, methinks I'll drive that prototype mixer straight from that square output. No way mate!. Phase jitter so bad that a 'scope has difficulty displaying the waveform. Zilch mention of this in the data sheet.

[...]

Yes. I read the thread. Admit I no longer have your patience in chasing down questionable components. Any component that dares to display 'oddities' is immediately out on it's ear. More and more though, I'm falling back to using those transistor things. They can be a bugger to design with and generate big drawings but aren't 'arf cheap and reliable. john

--
Posted via a free Usenet account from http://www.teranews.com

[snip]

It's right in the set-ups for Agent.

PhD's with soldering irons. Need I say more ?:-)

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
I love to cook with wine.      Sometimes I even put it in the food.

Not for Mozilla :-(

But I did find out how to search across directories so I split the emails into batches like you do. Will figure out the reply header some time but working on a laser thing on the other PC right now.

Ouch. Maybe take some burn gel with you next time.

--
Regards, Joerg

http://www.analogconsultants.com