Low offset, low noise op amp recommendation - Electronic Circuits Projects Diagrams Free

Oznog · 7th October 2004, 02:25 AM

I have a couple of silicon strain gauge pressure sensors which are inherently quite noisy (500Hz - MHz range), but I must have a high accuracy reading out of a 16 bit op amp. Oversampling was not helpful enough, so I need to construct a lowpass filter, but the ADC will have an unacceptable loss of accuracy with the high source impedance.

So, I need to add a 1:1 buffer after the filter. It needs to be as low offset as possible, as well as low noise since the whole point is to lower the noise.

It's powered by a single 5v supply and the signal on one sensor swings to 4.1, but the other can swing to 4.95v, which may mean I need to select another sensor since fewer buffers can go rail-to-rail in 5v (voltage dividers are bad for accuracy so I will be staying away). Power output and supply current are not an issue.

Any recommendations? There's just a crapload of op amps out there and I'm going to looking through specs for awhile.

plot · 7th October 2004, 10:08 AM

Not sure what you meant by 16 bit opamp exactly...

but i use this one often, has low offset, maybe it'll send you in the right direction:
http://focus.ti.com/docs/prod/folder...t/opa2132.html

Optikon · 7th October 2004, 02:30 PM

Quote:

Originally Posted by Oznog

I have a couple of silicon strain gauge pressure sensors which are inherently quite noisy (500Hz - MHz range), but I must have a high accuracy reading out of a 16 bit op amp. Oversampling was not helpful enough, so I need to construct a lowpass filter, but the ADC will have an unacceptable loss of accuracy with the high source impedance.

So, I need to add a 1:1 buffer after the filter. It needs to be as low offset as possible, as well as low noise since the whole point is to lower the noise.

It's powered by a single 5v supply and the signal on one sensor swings to 4.1, but the other can swing to 4.95v, which may mean I need to select another sensor since fewer buffers can go rail-to-rail in 5v (voltage dividers are bad for accuracy so I will be staying away). Power output and supply current are not an issue.

Any recommendations? There's just a crapload of op amps out there and I'm going to looking through specs for awhile.

A couple low noise choices to consider.

LT1028 / LT1037 from linear.com

OP184 from analog.com

OPA228 from ti.com

LM833 from national.com (very nice cost)

MAX4475 from maxim-ic.com

Happy hunting!

Roff · 7th October 2004, 09:25 PM

When you say oversampling, does that mean you already tried software-based filtering?

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7th October 2004, 02:25 AM	(permalink)
Oznog	Low offset, low noise op amp recommendation I have a couple of silicon strain gauge pressure sensors which are inherently quite noisy (500Hz - MHz range), but I must have a high accuracy reading out of a 16 bit op amp. Oversampling was not helpful enough, so I need to construct a lowpass filter, but the ADC will have an unacceptable loss of accuracy with the high source impedance. So, I need to add a 1:1 buffer after the filter. It needs to be as low offset as possible, as well as low noise since the whole point is to lower the noise. It's powered by a single 5v supply and the signal on one sensor swings to 4.1, but the other can swing to 4.95v, which may mean I need to select another sensor since fewer buffers can go rail-to-rail in 5v (voltage dividers are bad for accuracy so I will be staying away). Power output and supply current are not an issue. Any recommendations? There's just a crapload of op amps out there and I'm going to looking through specs for awhile.

7th October 2004, 10:08 AM	(permalink)
plot	Not sure what you meant by 16 bit opamp exactly... but i use this one often, has low offset, maybe it'll send you in the right direction: http://focus.ti.com/docs/prod/folder...t/opa2132.html

7th October 2004, 09:25 PM	(permalink)
Roff	When you say oversampling, does that mean you already tried software-based filtering?