I'm building an adc and amplifier circuit for sensing a differential signal out of a pressure sensor. My plan is to use a circuit very similar to what is seen below:

The total differential output from the pressure sensor will likely be quite small (less than 1mV) so the amplifier will have 30x or 100x gain so I am worried about noise on the output. The frequencies I want to measure are very low (1-30Hz) so I can put in an appropriately designed RC circuit. However, since noise is an issue, I was considering using a Sallen-Key low pass filter on each of the outputs from the amplifier so I can get a sharper drop off.

Does it make any sense to do this? I'm worried that voltage offset errors from the sallen-key amplifiers would change the results of the ADC conversion of the differential signal.

  • 2
    \$\begingroup\$ AD7982 is capable of 1 MSPS. Maybe just oversample your signal and filter in the digital domain? \$\endgroup\$ – The Photon May 12 '16 at 4:37
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    \$\begingroup\$ A bit of noise could be good for you if you are oversampling. atmel.com/images/doc8003.pdf \$\endgroup\$ – efox29 May 12 '16 at 6:17
  • \$\begingroup\$ Thanks for the comments. That's an interesting document. \$\endgroup\$ – viliam May 12 '16 at 16:22

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