Patent ID: 8593379

Claim:
An active matrix electroluminescent display device comprising an array of display pixels, each pixel comprising: an electroluminescent display element; and active matrix circuitry including at least one drive transistor for driving a current through the display element, wherein the device further comprises: means for determining an integrated brightness level of an image to be displayed by a plurality of pixels in a frame period; and means for controlling the at least one drive transistor of each pixel, the controlling depending on a respective input signal providing a drive level for the pixel and depending on the integrated brightness level, wherein the active matrix circuitry comprises current sampling circuitry for sampling an input drive current, the current sampling circuitry having a current sampling transistor in parallel with the at least one drive transistor, each of the current sampling transistor and the at least one drive transistor connected to a respective power supply line, the circuitry being arranged such that each of the current sampling transistor and the at least one drive transistor can supply current to the display element, wherein at least one of the supply voltages of the power supply lines is variable in dependence on the integrated brightness level of the image to be displayed in the frame period.