Regarding my previous question, I decided to use a “fully differential amplifier” to obtain a voltage gain of 10. The source and ADC are also differential. The source is unipolar and its output resistance is given as 100 Ohm. I want to amplify the +/-200mV source voltage by gain of 10 or more. ADC input can be set to +/-5V or +/-10V. Below I have drawn the schematics:
Above ADC and the amplifier are just representative. ADC is actually a channel of a differential ended data acquisition board. OPA 1632 represents a fully differential amplifier but it is designed for audio. My freq of interest is not audio, it is actually DC to 150Hz and need low noise as possible.
If this topology is correct, before I start to build this I noticed I have some inexperience about some critical decision.
I summarized the questions for clarity:
I want to use 5 meters of STP cable between the source and ADC. Should the amplifier be right after the source or right before the ADC?
As far as I understand the voltage gain is 1+R3/R1 = 1+R4/R2 where R3=R4 and R1=R2. But what values of resistors are reasonable?
R1, R2, R3 and R4 will have tolerances. In that case how can matched resistor arrays be configured to obtain better CM noise immunity?
(Schematic does not show an anti-aliasing filter)