Fast, Fet, Fifteen (volt rails.. opamp)

Hi all, quick question. I'm looking for a FET opamp to goose up a photodiode circuit. (make it faster) It's got +/-12V power rails, single opamp, and 8-Soic package. The oap827 looks OK,

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Slew rate is a little low. AD825 is better, but noisy... may not matter too much.
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There are the older OPA627/ 637 both kinda spendy.

Is there someone good that I missed? (I have AD825's in stock so will try that first.)

George H.

Reply to
George Herold
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THS4631 is one possibility--200-300 MHz, 900V/us slew, 7 nV flatband noise, 50 pA I_IB.

Cheers

Phil Hobbs

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Dr Philip C D Hobbs 
Principal Consultant 
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Reply to
Phil Hobbs

Great, thanks Phil... (added to DK cart) I maxed out my input current at 20 pA, so missed it*.

At present I've got a 1.5 MHz (GBW) opamp in there, 100 times faster will increase the BW by a factor of ten... I'm not sure I'm allowed to drive that fast. :^) Actually I wonder if that will be too fast? There is a lot of stray capacitance in the circuit... (switched RC gain stages) Big photodiode ~130 pF at -10V.. I'll have to push some numbers around.

George H.

*Hey, DK now let's you put in ranges for certain parameters! When did that happen?
Reply to
George Herold

For medium-speed things that aren't too cost-sensitive, the 10 MHz OPA140 is a pretty sweet part. Its main problem is that the SPICE model is super temperamental--it won't find an operating point unless the supplies are perfectly symmetrical, and frequently not even then.

.savebias newfoo.op internal .loadbias foo.op

is a big help. (You use a command window to copy newfoo.op on top of foo.op when you need a new starting point.)

Cheers

Phil Hobbs

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Dr Philip C D Hobbs 
Principal Consultant 
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Reply to
Phil Hobbs

Huh, I don't know that part. Kinda like the OPA192? Which has low Vos too.

GH

Reply to
George Herold

The OPA140 is a 40V JFET rather than CMOS, so its input CM range doesn't go to V+ but it is RRO. It has really low 1/f noise for a FET--the corner frequency is about 30 Hz.

They both have input noise curves that cut off at 1% of GBW, which worries me.

Cheers

Phil Hobbs

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Dr Philip C D Hobbs 
Principal Consultant 
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Reply to
Phil Hobbs

LT1028 has made you suspicious.

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John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  
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Reply to
John Larkin

Yer darn tootin'.

There I was going along fat dumb and happy, blissfully unaware that datasheets were now written by the marketing department, and *POW*. ;)

Cheers

Phil Hobbs

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Dr Philip C D Hobbs 
Principal Consultant 
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Reply to
Phil Hobbs

Maybe their spectrum analyzer only goes to 100 kHz. I could check the noise of the opa192 to 1 MHz.

George H.

Reply to
George Herold

George, sorry to hijack the thread, but you were looking for "Principles of Operation of the Rubidium Vapor Magnetometer" by A.L. Bloom

I found it at

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You can find many paywalled articles at Sci-Hub:

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More info at

"Subscription Journals Are Doomed Because of Sci-Hub's Big Cache of Pirated Papers, Suggests Data Analyst"

Posted by BeauHD on Thursday July 27, 2017 @07:20PM from the beginning-of- the-end dept.

An anonymous reader quotes a report from Science Magazine: There is no doubt that Sci-Hub, the infamous -- and, according to a U.S. court, illegal

-- online repository of pirated research papers, is enormously popular. But just how enormous is its repository? That is the question biodata scientist Daniel Himmelstein at the University of Pennsylvania and colleagues recently set out to answer, after an assist from Sci-Hub. Their findings, published in a preprint on the PeerJ journal site on July 20, indicate that Sci-Hub can instantly provide access to more than two-thirds of all scholarly articles, an amount that Himmelstein says is "even higher" than he anticipated. For research papers protected by a paywall, the study found Sci-Hub's reach is greater still, with instant access to 85% of all papers published in subscription journals. For some major publishers, such as Elsevier, more than 97% of their catalog of journal articles is being stored on Sci-Hub's servers -- meaning they can be accessed there for free. In a chat with ScienceInsider, Himmelstein concludes that the results of his study could mark "the beginning of the end" for paywalled research.

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Reply to
Steve Wilson

Elsevier, more than 97%

stored on Sci-Hub's

I'm not in favour of pirate sites, but I'm also not in favour of dirtbag ou tfits like Elsevier who prevent the public from reading research that we pa id for. Given what a joke peer-review is these days, their only added val ue is owning journals that confer prestige. (I do a fair amount of reviewin g, and the quality of both the MSes and other reviews has tanked in the las t 15 years.)

Cheers

Phil Hobbs

Reply to
pcdhobbs

outfits like Elsevier who prevent the public from reading research that we paid for. Given what a joke peer-review is these days, their only added v alue is owning journals that confer prestige. (I do a fair amount of review ing, and the quality of both the MSes and other reviews has tanked in the l ast 15 years.)

I think it is plain wrong that the paper I have paid tax for (the insitutio ns are funded that way and the Ph.D stundents likewise), are kept from me

So I have a IEEE subscription. But, many of the papers can be found outside the blocked sites anyway.

EDN also has some funny stuff going on. I get their newsletter emails, and they want me to sign up to see articles. But, just copy the article headlin e to Google and it pops up (they make is seem like the articles are special for EDN, but they are not)

Cheers

Klaus

Reply to
klaus.kragelund

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