A scalable highest available voltage selector circuit determines the highest of n input voltages and connects the highest voltage to an output. The circuit has at least n circuit branches, each of which comprises n−1 “comparator” FETs connected between an input voltage and an output node, and a diode-connected FET connected between the output node and a current source. The junction of the diode-connected transistor and current source provides a control signal used by the other branches. Each of a branch's comparator FETs have their gates connected to a respective one of the other branches' control signals, such that they are driven on regeneratively when the applied input voltage is the highest of the n input voltages. Each branch also includes n−1 “shorting” FETs connected across the diode-connected transistor, arranged to be driven off when the applied input voltage is the highest, but which are otherwise driven on.