CMOS-C Filter before amplifier

[Junus2012]

Hello,

I have a large differential sensor signal of 0.5 Vp-p. I use an ADC of 14 bits with full-scale voltage of 2 Vp-p. Therefore I set the gain of the instrumentation amplifier (In-Amp) to 4 to utilize the full dynamic range of the ADC and thus achieving the highest resolution of 14 bits.

After the In-Amp I use CMOS-C filter. However, now the input to the filter becomes 2 Vp-p, and because it relies on MOS resistor, such amplitude starts to introduce non-linear distortion at this amplitude.

I am thinking to put the filter before the In-Amp, but I face a technical problem with regards to the input common mode range between the filter and the sensor bridge. The alternative possible solution is to place a unity gain In-amp before the filter then I another in-amp with gain 4 after the filter.

I believe that a common approach is to always keep the filter in the last stage, otherwise the amplifier beyond it will amplify the noise level as well depending on its gain value.

I would like to have your discussion on this issue

Thank you in advance

Best Regards

 

[Junus2012]

For some reasons I don't know why my records has been removed from my profile, any way that is not important as the answer to my post