Favourite low offset op-amp

Pooh Bear · May 17, 2005

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

bernhard.kramer@lien.uhp- · May 17, 2005

Pooh Bear a écrit :

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

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

Pooh Bear · May 17, 2005

"bernhard.kramer@lien.uhp-nancy.fr" wrote:

Pooh Bear a écrit :

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

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.

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

Winfield Hill · May 17, 2005

Pooh Bear (Graham) wrote...

Bernhard Kramer wrote:
Pooh Bear a écrit:

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.

One of my favourite opamps is the OPA227. It has an offset of
75uV, 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.

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!

Snork!

--
Thanks,
- Win

Pooh Bear · May 17, 2005

Winfield Hill wrote:

Pooh Bear (Graham) wrote...
Bernhard Kramer wrote:
Pooh Bear a écrit:

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.

One of my favourite opamps is the OPA227. It has an offset of
75uV, 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.

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!

Snork!

That's consumer product for you !

You want to see an itemised BOM ?

Graham

Winfield Hill · May 17, 2005

Pooh Bear wrote...

Winfield Hill wrote:

Pooh Bear (Graham) wrote...
Bernhard Kramer wrote:
Pooh Bear a écrit:

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.

One of my favourite opamps is the OPA227. It has an offset of
75uV, 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.

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!

Snork!

That's consumer product for you !
You want to see an itemised BOM ?

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

Spehro Pefhany · May 17, 2005

On Tue, 17 May 2005 06:53:29 +0100, the renowned Pooh Bear
<rabbitsfriendsandrelations@hotmail.com> wrote:

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

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

Winfield Hill · May 17, 2005

Spehro Pefhany wrote...

On Tue, 17 May 2005, the renowned Pooh Bear wrote:

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.

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

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

--
Thanks,
- Win

John Larkin · May 17, 2005

On 17 May 2005 03:59:34 -0700, Winfield Hill
<hill_a@t_rowland-dotties-harvard-dot.s-edu> wrote:

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!

Snork!

Is that term in the Dictionary of Electronics?

John

Joerg · May 17, 2005

Hello Graham,

If you can afford to do auto-zero as Bill suggested and your opamp
budget really is 15 cents for a dual: Why not use ye olde LM324 and
clamp to zero? Ok, you'd have to spring another 5c or so for a BSS123 to
do the clamping but a quad LM324 can be had for around 10c.

Regards, Joerg

http://www.analogconsultants.com

Joerg · May 17, 2005

Hello Winfield,

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.

Yes. I wish they were teaching this kind of thinking at universities (at
least at mine they didn't). There is almost always a chance to do even
the most challenging designs with jelly bean components. Even though I
prefer M&Ms over jelly beans.

Regards, Joerg

http://www.analogconsultants.com

Jim Thompson · May 17, 2005

On Tue, 17 May 2005 21:11:20 GMT, Joerg
<notthisjoergsch@removethispacbell.net> wrote:

Hello Graham,

If you can afford to do auto-zero as Bill suggested and your opamp
budget really is 15 cents for a dual: Why not use ye olde LM324 and
clamp to zero? Ok, you'd have to spring another 5c or so for a BSS123 to
do the clamping but a quad LM324 can be had for around 10c.

Regards, Joerg

http://www.analogconsultants.com

Bill? Did I miss an actual technical contribution by Sloman ?

480)460-2350 | |
| E-mail Address at Website Fax

Joerg · May 17, 2005

Hello Jim,

Bill? Did I miss an actual technical contribution by Sloman ?

Yes, although he was suggesting the use of an LTC auto-zero amp which
are expensive.

I love auto-zeroing.

Me, too. But I like the old fashioned word "clamping" better. Even the
vintage tube TV sets did that already to set the proper black level.

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....

Way to go. It'll even work with a crude transistor amp.

Regards, Joerg

http://www.analogconsultants.com

Jim Thompson · May 17, 2005

On Tue, 17 May 2005 21:48:26 GMT, Joerg
<notthisjoergsch@removethispacbell.net> wrote:

Hello Jim,

Bill? Did I miss an actual technical contribution by Sloman ?

Yes, although he was suggesting the use of an LTC auto-zero amp which
are expensive.

I love auto-zeroing.

Me, too. But I like the old fashioned word "clamping" better. Even the
vintage tube TV sets did that already to set the proper black level.

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

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....

Way to go. It'll even work with a crude transistor amp.

Regards, Joerg

http://www.analogconsultants.com

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

Spehro Pefhany · May 17, 2005

On Tue, 17 May 2005 21:48:26 GMT, the renowned Joerg
<notthisjoergsch@removethispacbell.net> wrote:

Hello Jim,

Bill? Did I miss an actual technical contribution by Sloman ?

Yes, although he was suggesting the use of an LTC auto-zero amp which
are expensive.

I love auto-zeroing.

Me, too. But I like the old fashioned word "clamping" better. Even the
vintage tube TV sets did that already to set the proper black level.

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....

Way to go. It'll even work with a crude transistor amp.

It actually works *better* with a crude transistor amplifier.

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

John Larkin · May 17, 2005

On Tue, 17 May 2005 21:48:26 GMT, Joerg
<notthisjoergsch@removethispacbell.net> wrote:

Hello Jim,

Bill? Did I miss an actual technical contribution by Sloman ?

Yes, although he was suggesting the use of an LTC auto-zero amp which
are expensive.

I love auto-zeroing.

Me, too. But I like the old fashioned word "clamping" better. Even the
vintage tube TV sets did that already to set the proper black level.

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....

Way to go. It'll even work with a crude transistor amp.

Double-emitter choppers.

John

martin griffith · May 17, 2005

On Tue, 17 May 2005 09:50:06 -0700, in sci.electronics.design John
Larkin <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:

On 17 May 2005 03:59:34 -0700, Winfield Hill
hill_a@t_rowland-dotties-harvard-dot.s-edu> wrote:

Snork!

Is that term in the Dictionary of Electronics?

John

Tis now

martin

After the first death, there is no other.
(Dylan Thomas)

Jim Thompson · May 17, 2005

On Tue, 17 May 2005 15:12:11 -0700, John Larkin
<jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:

On Tue, 17 May 2005 21:48:26 GMT, Joerg
notthisjoergsch@removethispacbell.net> wrote:

Hello Jim,

Bill? Did I miss an actual technical contribution by Sloman ?

Yes, although he was suggesting the use of an LTC auto-zero amp which
are expensive.

I love auto-zeroing.

Me, too. But I like the old fashioned word "clamping" better. Even the
vintage tube TV sets did that already to set the proper black level.

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....

Way to go. It'll even work with a crude transistor amp.

Double-emitter choppers.

John

480)460-2350 | |
| E-mail Address at Website Fax

Jim Thompson · May 17, 2005

On Tue, 17 May 2005 16:05:53 -0700, John Larkin
<jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:

On Tue, 17 May 2005 15:43:53 -0700, Jim Thompson
thegreatone@example.com> wrote:

On Tue, 17 May 2005 15:12:11 -0700, John Larkin
jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:

On Tue, 17 May 2005 21:48:26 GMT, Joerg
notthisjoergsch@removethispacbell.net> wrote:

Hello Jim,

Bill? Did I miss an actual technical contribution by Sloman ?

Yes, although he was suggesting the use of an LTC auto-zero amp which
are expensive.

I love auto-zeroing.

Me, too. But I like the old fashioned word "clamping" better. Even the
vintage tube TV sets did that already to set the proper black level.

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....

Way to go. It'll even work with a crude transistor amp.

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
2 meter band. (5W

480)460-2350 | |
| E-mail Address at Website Fax

Rich Grise · May 17, 2005

On Tue, 17 May 2005 09:50:06 -0700, John Larkin wrote:

On 17 May 2005 03:59:34 -0700, Winfield Hill
hill_a@t_rowland-dotties-harvard-dot.s-edu> wrote:

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!

Snork!

Is that term in the Dictionary of Electronics?

It's an onomatopoeia, so probably not.

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

Cheers!
Rich

Favourite low offset op-amp

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