LMP91200: amplifier for differential pH sensor

Bob Day1

Part Number: LMP91200
Other Parts Discussed in Thread: LMP7721, INA116, LMC6042

I am aware of the LMP91200. However, we need to use a fully differential pH probe - see attached diagram - which has the contained liquid as its ground reference. Could you suggest an appropriate low bias matched (dual probably works) diff amp (or other circuit/part) to attain similar results as those of the 91200? Thank you

over 6 years ago

0 Jose Arteaga4 over 6 years ago

TI__Expert 5695 points

HI Bob,
Based you post you can't use the LMP91200 and will need a discrete/ dual amplifier solution. As you imagine there are lots of possible discrete amp solutions that could be used. I am forwarding this post to the amplifiers group to follow up with you.

Regards,
Jose

0 Collin Wells over 6 years ago in reply to Jose Arteaga4

TI__Guru 62095 points

Hello,

Take a look at OPAx128, OPAx129 or LMP7721 for very low input bias current op-amps.

0 Bob Day1 over 6 years ago in reply to Collin Wells

Prodigy 80 points

Thanks, Colin.

Yes, those will work from an input current standpoint, but would like to find either a fully diferential solution (INA116 comes to mind, but that's pushing the $$ edge) or a dual unit. Any other thoughts?

Regards

0 Collin Wells over 6 years ago in reply to Bob Day1

TI__Guru 62095 points

Hi Bob,

I'm not sure that we have a dual instrumentation solution with ultra-low input bias currents.

For a dual-amp consider the LMC6042. The bias currents aren't as low as the LMP7721 but they're still very low.

Amplifiers

Amplifiers forum

LMP91200: amplifier for differential pH sensor