I need to output the larger of two voltages (Va, Vb) (both of which could be in a range 0-30V), but drive the circuit using a 5V supply. A simple solution (using op-amps, FETs) is needed. I have looked at solutions using just an op-amp in comparator configuration, or an op-amp driving 2 MOSFETs, but since my Va, Vb could be smaller or greater than 5V, MOSFET switching does not seem to be an option (atleast with a trivial circuit).