An active matrix LED display device uses optical feedback for controlling the pixel drive transistors (2). The LED display elements are controlled to provide a pulsed output, and the optical feedback element (66,68) is controlled cyclically such that, for constant illumination of the optical feedback element (66,68) during a cycle, there is a substantially zero net output charge flow. This arrangement uses pulsed light output, and arranges the optical feedback to operate only in response to a corresponding pulsed light input. In this way, ambient light, which will be uniform over the time period of the cycle of operation, will not influence the optical feedback system. In this way, the system is not influenced by ambient light conditions.