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My question is simple. I'm designing a circuit and read some articles saying that you need to provide a DC bias current return path. These articles always referenced using them with floating inputs and when ac coupled. I've also seen this referenced in many adc datasheets. I have a return path for the inputs of my amp. My question is do I need a return path between the amp and adc or would that be taken care of innately by the amp?

schematic

simulate this circuit – Schematic created using CircuitLab

My design is like the bottom one. I have quite a few amps connected to the adc so if the resistor is unnecessary that would simplify the design a bit. Thanks for any insight you guys can provide. Not sure if this affects anything but I'm using instrumentation amps.

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  • \$\begingroup\$ a good INA improves can improve CMRR on some ADC's with attention to guarding details in Ap notes and CM range , shielding, filtering with CM chokes etc as required and suppressing interference from. motor pulse currents etc by same methods. Only need R on some uA rail-rail output types as datasheet will specify if required \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Oct 29 '16 at 18:07
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The DC bias can be provided by the opamp. However, some opamps may do better than others. Some ADCs are harder to drive than others. Unless you know how to analyze the opamp and ADC specs, I would use the opamp model that's recommended by the ADC application sheet.

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  • \$\begingroup\$ Ok so if I'm understanding correctly, as long as I know that the inamp can drive the adc I wont have to worry about the resistor (atleast for the dc bias current return path). I chose this amp for its specific qualities so I cant change that. Im not too worried about noise after the amp. \$\endgroup\$ – K Dash Oct 29 '16 at 20:30

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