Circuit for connecting externally power instrument to MCU
This schematic is rather useless :


It has low input impedance: if the source has, say, 50-100R output impedance, which is common, then your input voltage divider will be off by quite a wide margin.
It has unbalanced input impedances, and thus nearly non-existent CMRR


If you don't need balanced, forget about it, use a voltage divider with much higher resistor values, and a follower. Or no follower, if the bandwidth is now.

If you need a balanced/differential receiver, a much better solution would be a real instrumentation amplifier like  AD8421. Its CMRR is humongous, and as a bonus, it will tolerate input overvoltage up to 40V above the opposite rail, so your inputs will not blow even if your board is unpowered and connected to a powered source.

However, it will not work on your 3V3 supply. 

If you have other supplies on your board, then good. If all you have is 3V3 then you could look for a similar chip which will be compatible with your supply.