A comparator has an input stage having (i) resistor-coupled super source-follower circuits that convert differential input voltages into differential currents and (ii) hysteresis current-injection circuits that inject hysteresis currents into the differential currents. An output stage processes the differential currents to control the comparator output. Common-mode (CM) detection circuits inhibit some of the differential currents from reaching the output stage if the CM voltage is too close to a voltage rail of the comparator. The comparator is able to operate at CM voltages over the entire rail-to-rail range with constant hysteresis voltage.