Active matrix display devices
An active matrix display device, such as an AMLCD, having sets of row and column address conductors ( 18, 19 ) connected to an array of colour picture elements ( 12 ) arranged in columns of one colour and with adjacent columns being of different colours, and drive means ( 21, 23, 25 ) for supplying selection and data signals to the sets of address conductors uses a plurality of serial charge redistribution digital to analogue conversion means ( 30 ) to convert multi-bit digital data signals supplied to the column address conductors ( 19 ) into analogue voltage levels for use by the picture elements. Each conversion means uses the capacitances of two column conductors between which charge is shared by conversion switches ( 31 ). The two column conductors associated with a conversion means are selected to be column conductors associated with picture elements columns of the same colour, preferably adjacent column conductors associated with the same colour. This leads to reduced conversion errors and consequential unwanted display artefacts.
1 . An active matrix display device comprising a row and column array of picture elements, sets of row and column address conductors for selecting rows of picture elements and providing data signals to the picture elements of a selected row respectively, drive means for supplying selection signals and multi-bit digital data signals respectively to the set of row address conductors and the set of column address conductors, in which the multi-bit digital data signals supplied to the column address conductors are converted into analogue voltage levels for use by the picture elements by a plurality of serial charge redistribution digital to analogue conversion means, each conversion means comprising at least first and second capacitances interconnectable by at least one conversion switch and between which charge is shared, and in which the first and second capacitances of a conversion means are provided by the capacitances of two column address conductors, wherein the picture elements in a column are of the same colour and adjacent columns of picture elements are of different colours, and wherein the first and second capacitances of a digital to analogue conversion means comprise column address conductors associated with the same colour of picture elements.
2 . An active matrix display device according to claim 1 , wherein the two column conductors of a conversion means comprise adjacent column conductors associated with the same colour picture elements.
3 . An active matrix display device according to claim 1 , wherein for each conversion means the picture elements in a row associated with the conversion means are connected to different row address conductors.
4 . An active matrix display device according to claim 3 , wherein the picture elements in a column are connected alternately to the different row address conductors.
5 . An active matrix display device according to claim 1 , wherein the device comprises a liquid crystal display device.