Favourite low offset op-amp

Sounds like a job for an auto-zeroing op amp. Linear Technology have been making them for many years, though National Semiconductor and Analog Devices also introduced useful products some years ago.

------------ Bill Sloman, Nijmegen

Snork!

If you wish, but it'd be better to discuss your application and circuit, to see why you need 0.1mV, and if there's a workaround that'll allow you to use cheaper opamps.

TI's OP07DD, 60uV typ, 32.5 cents qty 2500, not bad, good call Spef!

There's no contest, use an OP-07D

Best regards, Spehro Pefhany

Is that term in the Dictionary of Electronics?

John

That's > 10x what I want to pay ! I could live with 100kHz GBWP - lol !

My idea of low cost is around 15 cents per dual op-amp in quantity !

Graham

Pooh Bear a écrit :

One of my favourite opamps is the OPA227. It has an offset of < 75 uV, is reasonable fast (8MHz, 2 V/us Slew Rate, but the OPA228 is faster), and runs off +/- 18 V max. It's a low cost opamp with good characteristics, IMHO. But look out for its input bias, it is around 10 or 100 nA.

Best, Bernhard

That's consumer product for you !

You want to see an itemised BOM ?

Graham

Bill? Did I miss an actual technical contribution by Sloman ?:-)

I love auto-zeroing.

Once upon a time, I even built a micro-voltmeter, using LM324's, to measure voltage drop on PCB tracks, to locate shorts.

Zero, measure, zero, measure....

...Jim Thompson

Ah, yes. DC restorers. I grew up in a radio/TV repair shop ;-)

I used 'HC4016's to do the work. Actually left out a step above, should be...

Zero, measure, hold, zero, measure, hold....

With non-overlap between each, to keep caps from getting tweaked.

...Jim Thompson

Double-emitter choppers.

John

You're showing your age, John. And they weren't all that wonderful... CMOS is MUCH better.

...Jim Thompson

Varicap parametric bridges.

John

What did they call the big-ass ones.

I vaguely remember using some kind of varactor to triple me up to the

...Jim Thompson

It's an onomatopoeia, so probably not.

I think "bang-bang" might be, however. ;-)

Cheers! Rich

Jim, are you mellowing out in your old age? ;-)

You built stuff? I thought all you did was ideate and simulate. ;-) Oh, right - at our age, we don't have time for all that trimming and crap, right? ;-)

Cheers! Rich

Burr-Brown did a very impressive potted-brick opamp using modulated varicaps in the front end; CMRR was about infinite, as the entire input circuit was transformer-coupled. I think Bob Pease did an article on it. I seem to recall that TI did a monolithic varicap opamp at some point... I may have a datasheet in The Dungeon.

Paramps are cool. Somebody did a paper on using ceramics caps as active gain elements, and I have a paper on making nonlinear transmission lines (shock lines) using the nonlinearity of ceramic caps.

Just because I know about this stuff doesn't mean I'm old enough to have experienced it all first-hand.

John

Yes it do ;-)

...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 | |

Reminds me when we first met the daughter-in-law's family.

My son, bride-to-be and her mother show up in the bride's Honda Civic.

They say that father is on the way.

All of a sudden the house is shaking, and this crazy, hippy-looking guy, with a bandanna, comes up the hill on a Harley chopper... so loud that all the neighbors pour out of their houses.

It's the father-of-the-bride. Turns out he's a big-time dealer in Harley parts in LA (now moved to Palm Springs).

Then he took off the bandanna... it had a velcro closure. I gave him a ration of s*it for lack of authenticity ;-)

...Jim Thompson