As you see above after the multiplexer there is an instrumentation amplifier IA.
Since this is a differential amplifier IC, its input stage must be a differential pair topology as follows:
Now my questions are:
1-) All the data-acquisition boards I used measured the actual voltage applied, and did not amplify them. Normally if one sets the daq input range to -/+10V, and if one applies 2V with to daq's inputs, the daq will meaure 2V. Here my first question is, what is the need for the IA stage if it doesn't amplify? Is that common mode rejection? And what if the daq used for single-ended inputs? Would the IA still have a use? Why not directly coupled to ADC converter?
2-) If I swing the input voltage to the daq from -10V to 10V this is a large change. Wouldn't it cause non-linearity in the IA's differential input stage(large-signal analysis)? How is this be linearized?