An active matrix display device has an array of display pixels, each pixel comprising a current-driven light emitting display element (2), a drive transistor (22) for driving a current through the display element and pixel circuitry including an optical feedback element (38) for controlling the drive transistor to drive a substantially constant current through the display element for a duration which depends on the desired display pixel output level and an optical feedback signal of the optical feedback element. An output configuration is applied to the display which includes values for the pixel power supply voltages, the field period and an allowed range of pixel drive levels. The output configuration is varied in response to ageing of the display element. In this device, an output configuration is varied as the device ages, so that the optical feedback system can continue to provide compensation for differential ageing of the display elements for a longer period of use of the display.