I did a bit of searching and I don't get it. What is really the difference between single supply and dual supply op amps? Voltages are just a potential difference. Op amps usually do not have a ground pin so they should have no idea if I am connecting +-15 V or +30V,0V it should still drive the output such that the difference between the inputs is minimal. I understand that you want to keep the input and output voltages close to the mid point of the rails, so the transistors are in their sweet spot. But how can the op amp help with that? And maybe there are issues with power supply/common mode rejection, but if I buy a single supply or a dual supply device what is different in the device that I get (except for the labelling of the pins)? Edit: I had an idea. Is a single supply op amp just a rail-to-rail amplifier that can go to the lower rail, but not necessarily to the upper rail?