In an active matrix electroluminescent display device a storage capacitor
(24) is provided in each pixel (10) for storing a voltage to be used for
addressing a drive transistor (22) which controls the illumination of the
electroluminescent display element (20) and gated discharge
photosensitive means (36), for example a phototransistor, are provided
for discharging the charge storage capacitor in dependence on the display
element's light output. Operation of the gated photosensitive means is
controlled by the output of an inverter (50) whose input is coupled to
one side of the storage capacitor. Upon the storage capacitor reaching a
predetermined discharge voltage, the gated photosensitive means (36) is
turned on by switching of the inverter, thereby rapidly discharging the
capacitor and turning off the display element. The use of an inverter in
this way ensures a fast, robust, and well controlled switching action to
terminate light output.