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Following is a made up example just to make the question clear:

enter image description here

In some cases when using an IC, it requires dual supply for its rails. And in that case such as above circuit, if we had single supply option such as 12V or any single supply instead of +/-6V, how should be the biasing done considering the circuit above?

So the system ground is MCU ground which is the laptop USB ground and in the circuit above the circuit ground and the system ground is same.

But if we use a single supply such as 12V supply, should we bias the negative rail and Vsig with Vcc/2? And how to couple it to MCU/system ground in that case?

Taking the example in the question and showing the modification for it would be better to see in the answer.

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  • \$\begingroup\$ The csse is not very specific. It depends on what the signal source is; what voltage ranges you expect to support on input and output, and which op-amp it is and what it is capable of. \$\endgroup\$
    – Justme
    Jan 3, 2023 at 6:30
  • \$\begingroup\$ It doesn’t have to be opamp but any IC like an inamp requiring dual supply. Take max specs as ideal. Its a question out of curiosity. \$\endgroup\$
    – pnatk
    Jan 3, 2023 at 6:34
  • \$\begingroup\$ It still depends on what your specs are and if the amp has rail to rail inputs and outputs. Because if it doesn't, it kind of makes no sense to split it into +6 and -6 V if the amp can't output 5V for max range, and MCU can't be fed with voltages below 0V. \$\endgroup\$
    – Justme
    Jan 3, 2023 at 6:43
  • \$\begingroup\$ Mcu can be fed by biasing its input. Forget about that part it could be a Daq which can handle negative input as well. You missing the essence of the question. Im not gonna comment more on it. Just skip it let someone else answer. \$\endgroup\$
    – pnatk
    Jan 3, 2023 at 6:58
  • \$\begingroup\$ Voting to close as missing necessary detail, as discussed above. Pnatk, there's at least two people who would seem to be missing the "essence of the question"; could you help us by editing your question then and more explicitly and clearly ask about that? Because to answer the question that you did ask in your question, one would need the info that Justme asked for. \$\endgroup\$ Jan 3, 2023 at 8:41

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But if we use a single supply such as 12V supply, should we bias the negative rail and Vsig with Vcc/2? And how to couple it to MCU/system ground in that case?

No, if you wanted to use a 12 V supply instead of +/- 6 V you would connect the negative of the 12 V supply to where -6 V was, and bias the ground points at Vcc/2.

You would then either have to connect Vcc/2 to the MCU ground or connect the 12 V negative to the MCU ground and capacitively couple the output to the MCU input.

Whatever means you use to derive Vcc/2 would need to be able to supply enough current, depending on the load it could be a resistive divider or a rail-splitter using active devices.

schematic

simulate this circuit – Schematic created using CircuitLab

With this the signal to the MCU would be able to swing both positive and negative probably +/- 4 V to +/- 6 V depending on the opamp, so you would need to make sure that it stays within the capabilities of the MCU input.

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    \$\begingroup\$ Another approach to biasing can be to make the virtual ground (the mid-point between R1 and R2) "soft" instead "stiff". For this purpose, we can remove C1 and Ri and directly connect the inverting input to the midpoint. R1||R2 will serve as Ri. Of course, V1 should be filtered. \$\endgroup\$ Jan 3, 2023 at 16:44

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