Instrumentation Amplifier Output Error Term "independent of gain"!

Hooman Hashemi

Hello All,

Do any Precision experts here have any opinions on the question posed in the High Speed forum (link below) related to output offset voltage which seems to not-vary with gain?

http://e2e.ti.com/support/amplifiers/high_speed_amplifiers/f/10/p/402095/1425392#1425392

If so, please chime-in on the original E2E site.

Regards,

Hooman

over 10 years ago

0 Pete%20Semig over 10 years ago

TI__Mastermind 25825 points

Hello Hooman,

I believe you are correct with your last post in the aforementioned thread. It is likely that the customer is violating the input common-mode voltage or output swing range of his custom 2-op amp instrumentation amplifier. If one of the op amps (or both) is/are operating in a non-linear region, it would appear as though the gain is incorrect or the output is 'stuck'. Perhaps the customer would be interested in the following articles. Though they discuss 3-op amp instrumentation amplifiers, the idea is the same.

www.edn.com/.../Instrumentation-amplifier-VCM-vs-VOUT-plots--Part-1
www.edn.com/.../Instrumentation-amplifier-VCM-vs--VOUT-plots--part-2
www.edn.com/.../Instrumentation-amplifier-VCM-vs--VOUT-plots--Part-3

I hope this helps.

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Instrumentation Amplifier Output Error Term "independent of gain"!