A display device has an array of display elements (2) each driven by an input provided on a data conductor (6). These inputs are generated by data conductor addressing circuitry (9) which has a plurality of controllable driver circuits (32,34,40), each for providing an input to an associated data conductor. The number of controllable driver circuits is at least one greater than the number required for providing data to all data conductors. A reference driver circuit (30) is used for calibrating at least one of the controllable driver circuits whilst the other controllable driver circuits provide inputs to the data conductors. This provides a reduction in the spread of driver circuit outputs by calibration of the driver circuits using a reference driver circuit.