I want to amplify a bridge signal (with maximum accuracy <50ppm) to feed it to an ADC. Normally, for DC exication, this is done by an INA. But as all INAs have limited CMRR, especially at higher frequencies. So they produce ugly artifacts when the common voltage
is rectangle shaped (~200Hz) and have large swing of up to 14Vpp.
An EMI input filter lowers those artifacts a little, but doesn't make it shorter.
My thought is to use two INAs with opposite inputs paralelled to get a differential signal between the INAs outputs, that can be fed to a fully differential ADC-driver.
The chopping artifacts should be similar on both INAs, so they would become solely common mode, that would be highly attenuated
by the differential ADC-driver. I know that gain mismatch will produce a common-mode signal.
I didn't see such a circuit anywhere as a suggestion. What are the pitfalls / drawbacks of such a circuit?
Is there any other cirquit available to handle this signal best?
(=> see my other unanswered question "AD8429: CMRR worse than stated in data sheet" for oscilloscope pictures)
Any kind of help would be very much appreciated.