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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.

+/-17V is a bit high for this sort of amplifier - the Linear Technology LTC1150 is the only one I know of that comes close, with a maximum supply voltage of +/-16V. It isn't cheap - at about $5 in small quantities, while the lower supply voltage parts come in under a dollar. and the input currents aren't all that low, at around a nanoamp, while the lower supply voltage parts claim tens of picoamps, but the input offset voltage is 0.5uV typical, +/-10uV worst case.

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

Reply to
bill.sloman
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Snork!

--
 Thanks,
    - Win
Reply to
Winfield Hill

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.

--
 Thanks,
    - Win
Reply to
Winfield Hill

Hi all,

I have an application where I'm looking for a low input voltage offset op-amp. I'd like 100uV or so typical and don't want to pay much. Lowish input current is desirable too.

Speed isn't an issue, nor is very low noise or single supply operation. In fact I *want* to run it off +/- 17V.

It's not an area I'm intimately familiar with.

Anyone got any suggestions ? Low cost remember !

Cheers, Graham

Reply to
Pooh Bear

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

--
 Thanks,
    - Win
Reply to
Winfield Hill

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

Best regards, Spehro Pefhany

--
"it\'s the network..."                          "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
Reply to
Spehro Pefhany

Is that term in the Dictionary of Electronics?

John

Reply to
John Larkin

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

Reply to
Pooh Bear

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

Reply to
Bernhard.Kramer

That's consumer product for you !

You want to see an itemised BOM ?

Graham

Reply to
Pooh Bear

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

--
|  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.
Reply to
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

--
|  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.
Reply to
Jim Thompson

Double-emitter choppers.

John

Reply to
John Larkin

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

...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.
Reply to
Jim Thompson

Varicap parametric bridges.

John

Reply to
John Larkin

What did they call the big-ass ones.

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

2 meter band. (5W :)

...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.
Reply to
Jim Thompson

It's an onomatopoeia, so probably not.

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

Cheers! Rich

Reply to
Rich Grise

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

Reply to
Rich Grise

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

Reply to
John Larkin
[snip]

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 | |

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

Reply to
Jim Thompson

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