In an active matrix electroluminescent display device, a storage capacitor (24) is provided for storing a voltage to be used for addressing a drive transistor (22). A discharge photodiode (27) is provided for discharging the storage capacitor in dependence on the light output of the display element, and an input data voltage applied to the pixel is changed by an amount corresponding to the threshold voltage of the drive transistor. The changed data voltage is applied between the gate and source of the drive transistor.In this device the initial voltage on the gate of the drive transistor is modified so as to remove the dependency of the light output on the threshold voltage, so that threshold voltage variations can be tolerated.