I've got two differential driver circuit designs that take a single ended input and provide as output a buffered pair of +1 and -1 times the input and I'm struggling to understand the difference between the two.
In Circuit A, the inverting input to the bottom op-amp (U104B, configured to have gain +1) is attached to ground via R117. This is the "standard" topology as far as I can tell, and I understand how it works. (Note that the labels appear to be wrong, so the upper op-amp output labelled "Diff Out+" has gain -1 and the lower labelled "Diff Out-" has gain +1.)
In Circuit B on the other hand, the equivalent gain +1 op-amp, U12A (the upper one), has its inverting input connected to the input signal via R41. The non-inverting input is also connected to the input signal directly.
Why might someone connect the inverting input of a gain +1 op-amp to the input signal and not to ground like in the "standard" non-inverting op-amp topology? Lower noise perhaps? Better common mode rejection? (I'm not concerned about the op-amp types nor the extra resistors and capacitors at the output and feedback - just the differences between the inputs in the two circuits).