Active matrix display devices and methods of driving the same

An active matrix display device comprises an array of pixels arranged in rows and columns and a column driver circuit for providing pixel drive signals to the columns of pixels. The column driver circuit comprises an array of current source circuits, a respective current source circuit being provided for each column of pixels, and each current source circuit comprises a current source (70; 80; 90), an output driver (71), a storage capacitor (72) connected to the output of the output driver; and a supply switch (78) for controlling the time during which the current source supplies current to or drains current from the storage capacitor (72), thereby determining the output voltage of the output driver.; The device further comprises a mapping means (86) for deriving from a pixel drive level a digital value which represents a time period for the control of the supply switch (78) of each current source circuit.