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On TI's datasheet, it specifically lists EEG as one of INA332's potential uses.

EEGs are microvolt level signals, and the INA332 has input offsets of +/- 2 milliVolts.

73db CMRR is quite low, but I argue the input offsets make it impossible to measure a microvolt level signal effectively.

This is an instrumentation amplifier "Designed for low cost"... however I would argue it is not difficult, but physically impossible to pick up an EEG signal using this IC.

http://www.ti.com/lit/ds/sbos216b/sbos216b.pdf

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  • \$\begingroup\$ eeg machines were built using tubes, so I suspect its not physically impossible to get these to work.... \$\endgroup\$ – Henry Crun Apr 20 '18 at 0:16
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    \$\begingroup\$ The INA332 may not be the best choice, merely the lowest cost. The AD524 is an excellent instrumentation amp with both input and output offset adjustments, but very expensive. No matter what you use, for EEG you will need to have DC offset null adjustments and maybe a low pass filter as a servo-loop. EEG equipment often uses DSP to extract the wanted signals from background noise. \$\endgroup\$ – Sparky256 Apr 20 '18 at 0:43
  • \$\begingroup\$ You can calibrate it out with software \$\endgroup\$ – EE_socal Apr 20 '18 at 1:02
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    \$\begingroup\$ @EE_socal You made me laugh. Whenever we're in a project meeting to bring out a new instrument solving a uniquely difficult problem that, to date, has never yet been solved (like a temp sensor from -200 C to +1850 C with calibrated accuracy over range at 100 mK for the space shuttle), I always just deal with all the detailed and complex barriers by saying, "Don't worry, we'll just calibrate it out in software." Can't get a sustainable fusion reaction? No problem, "We'll just calibrate that out in software." ;) I've learned to duck pretty well. :) \$\endgroup\$ – jonk Apr 20 '18 at 1:15
  • \$\begingroup\$ The millivolt offsets mentioned are nothing compared to electrode offsets at the skin/electrode junction. \$\endgroup\$ – Scott Seidman Apr 20 '18 at 2:05
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You can decrease or eliminate the offset by changing the voltage on the REF pin, as detailed on page 11 of the datasheet. Since it has a pretty reasonable offset time stability of +-0.4uV/month, this should be fine for eeg (which is apparently 10-100uV externally measured). The temperature stability is a little higher at 5uV/C, but still manageable.

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It would make an OK input stage for an EEG amplifier. It would be backed up with a high pass of low cutoff freq, to remove offset, and op amps for gain.

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