Lighting system embodiments are provided to energize and calibrate strings of light-emitting diodes. These embodiments are particularly useful for calibration of strings of light-emitting diodes that are arranged to provide backlighting of liquid crystal displays. The systems are structured around the use of a single comparator that is multiplexed to facilitate calibration of a plurality of current sources. The systems can be adapted for use in displays in which different techniques (e.g., “analog dimming” and “pulse-width modulation”) are used to vary the brightness of the display. The systems remove the need for special structures (e.g., fuse arrays, special test equipment, and interfaces).