An active matrix electroluminescent display device comprises an array of
display pixels. In each pixel, a first switch connects power from a power
supply line to the display element and a second switch routes current
from a current-measurement supply line to the display element. The gate
voltage applied to a drive transistor is controlled by a feedback system,
such that control voltage is controlled in closed loop manner to achieve
the desired current. The control voltage can then be used for subsequent
addressing of the pixel.