Abstract: An active matrix display device comprises an array of display pixels provided over a common substrate. Each pixel has a voltage-programmed current source circuit, a drive transistor and a light sensitive device for sensing the display element light output. The light sensitive device provides a current dependent on the display element output, and the light sensitive device and the current source circuit define a feedback control loop which controls the voltage provided to the gate of the drive transistor. This pixel circuit uses a current source circuit to provide a gate voltage to a drive transistor. This enables the current source circuit to operate at low current levels, and therefore under low voltage stress.

Abstract: An active matrix display includes a display element for producing a visual output when the display element is driven with a constant current, and drive circuitry for controllably driving a substantially constant current through the display element. The drive circuitry includes a two-transistor inverter having an inverter input and a common node output, and the common node output of the inverter is connected, directly or indirectly, to supply or control the current passing through the corresponding display element.

Abstract: A matrix display device (60) comprises an array of pixels for producing a display output in response to drive signal voltages using an inversion drive scheme. Display artefacts, especially flicker, are corrected for by connecting together, in parallel, two pixels (31), previously addressed with respective drive signal voltages of opposite polarity, and measuring a residual voltage caused by a difference in charge stored on the two pixels due to a DC offset present in the pixels. The measured voltage is used to modify subsequent drive signal voltages for the pixels in order to reduce the measured voltage, i.e. towards zero, thus reducing display artefacts caused by the DC offset in the pixels. The invention is particularly applicable to transmissive type liquid crystal display devices.

Abstract: An electroluminescent (EL) display device comprises an array of display pixels, each display pixel comprising an EL display element and a driving circuit. A digital pixel drive signal determines whether the pixel is on or off, and a selected one of a plurality of supply voltages is switched to the EL display element. This device enables a digital drive scheme to be implemented, but the provision of a plurality of different supply voltages enables a grey scale to be implemented without requiring time or area ratio systems to be employed. Alternatively, the device of the invention can allow time or area ratio techniques to be improved.

Abstract: An active matrix electroluminescent (EL) display device comprises a matrix array of display cells (10) arranged in rows and columns, each cell comprising an EL display element (20) and driving circuitry. The cells are arranged in groups (12) which may constitute pixels. Each group of cells forms a series arrangement arranged so a data signal applied to the first cell in a series arrangement, via an associated data line (14), can be transferred to a neighbouring cell in the same group, and so on for subsequent cells in the group, upon application of a control signal applied to an associated control line (15). This device enables a digital drive scheme to be implemented. The provision of grouped display cells arranged so as to be driven in this way enables a grey scale to be implemented using fewer data lines (14) than usual.

Abstract: An electroluminescent (EL) display device comprises an array of display pixels, each display pixel comprising an EL display element and a driving circuit. A digital pixel drive signal determines whether the pixel is on or off, and a selected one of a plurality of supply voltages is switched to the EL display element. This device enables a digital drive scheme to be implemented, but the provision of a plurality of different supply voltages enables a grey scale to be implemented without requiring time or area ratio systems to be employed. Alternatively, the device of the invention can allow time or area ratio techniques to be improved.

Abstract: An EL display device is operable in analogue and digital modes. In the analogue mode a current is supplied to the EL display elements (2) in dependence on a data signal (6) supplied to the pixel, and in the digital mode one of two voltages is provided across the EL display elements in dependence on the data signal supplied to the pixel. This enables the display to have a low power standby mode in which a digital drive scheme is implemented. This is particularly appropriate for static images and preferably for images without grey scales. The first mode is the normal current addressing mode.

Abstract: A matrix display device (60) comprises an array of pixels for producing a display output in response to drive signal voltages using an inversion drive scheme. Display artefacts, especially flicker, are corrected for by connecting together, in parallel, two pixels (31), previously addressed with respective drive signal voltages of opposite polarity, and measuring a residual voltage caused by a difference in charge stored on the two pixels due to a DC offset present in the pixels. The measured voltage is used to modify subsequent drive signal voltages for the pixels in order to reduce the measured voltage, i.e. towards zero, thus reducing display artefacts caused by the DC offset in the pixels. The invention is particularly applicable to transmissive type liquid crystal display devices.