All FPGAs need at least a low core voltage (e.g. 1.2 V) and a high auxilary and IO supply voltage (e.g 2.5 or 3.3 V). IO voltage supplies are required according to the application and have to be added, if not already present for the basic FPGA supply, e.g. 3.3 V for general logic, 2.5 V for LVDS, 1.8 or 1.5 V for RAM interfaces. As said, you have to select a supply voltage for each bank of IO pins. Simple designs can use an unified supply voltage for all IOs, typically 2.5 or 3.3 V.