I am trying to design a system that needs 0 to 20V precise output span. I just get confused that do we need 1V headroom on the negative supply when outputing a unipolar voltage? The datasheet uses +6V/-1V supplies for the testing of +5V span. So in my case, do I need +21V/-1V supplies or a +21V/0V unipolar supply will be enough?
Thanks a lot,