Question: I have a unity gain differential op amp, using a grounded dual supply, with both inputs AC coupled.

Does the inverting input need a dedicated path to ground or can the DC bias current find its way to ground via the power supply?

[![enter image description here](https://i.stack.imgur.com/N8nUx.gif)](https://i.stack.imgur.com/N8nUx.gif)

I've searched around and haven't been able to find much regarding this particular configuration. Most of the information I've found talks about single supplies and/or op amps with only one input AC coupled.

If it matters, the op-amp I'll be using is a TL07X.

Answer: 
You're fine, the inverting input has a path for bias current through the feedback resistor, and of course the non-inverting input has the resistor to ground.

Both inputs have a dc path to ground, which is the important consideration.
The best way to understand and explain circuits in an intuitive way is to show where currents flow (see [my Codidact paper 1](https://electrical.codidact.com/posts/284816)) and what voltages are in circuits ([my Codidact paper 2](https://electrical.codidact.com/posts/284860)).

Here the OP is interested in where the input bias currents flow. That is why I have shown in my Fig. 1 only their paths on a simplified conceptual circuit diagram of a part of an internal op-amp structure.

[![Input bias currents - paths](https://i.stack.imgur.com/s13f5.jpg)](https://i.stack.imgur.com/s13f5.jpg)

Fig. 1. A conceptual op-amp circuit diagram with input bias currents visualized.

It can be supplemented with (thicker) loops representing the collector currents flowing in the input and output stage (see my Fig. 2).

[![Input bias currents - all paths](https://i.stack.imgur.com/OoAEc.jpg)](https://i.stack.imgur.com/OoAEc.jpg)

Fig. 2. A conceptual op-amp circuit diagram with all currents visualized.

It is interesting to see that the input bias current I- entering the inverting op-amp input is provided by both the positive power supply V+ and negative V- (connected in series) while the input bias current I+ entering the non-inverting input is provided only by the negative power supply V-.