Abstract: A transistor control circuit (74) comprises a source-gated thin film transistor (70), an input for receiving a drive voltage representing a desired control of the source-gated transistor and a current source (82) for causing a known current to pass through the source-gated transistor (70). A first capacitor (78) stores a resulting gate-source voltage of the source-gated transistor when the known current is passed through the source-gated transistor. The drive voltage is modified using the resulting gate-source voltage, and the modified voltage is used in the control of the source-gated transistor. This control can provide a translational shift in the operating characteristics of the transistor, and it has been found that this can compensate for ageing of the transistor, for non-uniformity between different devices, and for temperature variations.

Abstract: A photo transistor has an active region spaced from a source by barrier. A drain is laterally spaced from the active region. Light incident on the active region creates electron-hole pairs. Holes accumulate at the barrier and modulate the effective barrier height to electrons. A gate reset voltage then is applied to gate which lower the barrier allowing the holes to escape.

Abstract: A transistor has a source electrode (22) on the opposite side of a semiconductor body layer (10) to a gate electrode (4) insulated from the body layer (10) by gate insulator (8). The source electrode (22) has a potential barrier to the semiconductor body layer (10), for example a Schottky barrier. At least one drain electrode (54) is also connected to the semiconductor body layer (10). A suitable source-drain voltage and gate voltage depletes the region of the semiconductor body layer adjacent to the source electrode (22), and then source-drain current is controlled by the gate voltage.

Abstract: A photo transistor has an active region spaced from a source by barrier. A drain is laterally spaced from the active region. Light incident on the active region creates electron-hole pairs. Holes accumulate at the barrier and modulate the effective barrier height to electrons. A gate reset voltage then is applied to gate which lower the barrier allowing the holes to escape.

Abstract: A photo transistor has an active region spaced from a source by barrier. A drain is laterally spaced from the active region. Light incident on the active region creates electron-hole pairs. Holes accumulate at the barrier and modulate the effective barrier height to electrons. A gate reset voltage then is applied to gate which lower the barrier allowing the holes to escape.

Abstract: A photo transistor has an active region (24) spaced from a source (28) by barrier (26). A drain (20) is laterally spaced from the active region (24). Light incident on the active region creates electron-hole pairs. Holes accumulate at the barrier and modulate the effective barrier height to electrons. A gate reset voltage then is applied to gate (4) which lower the barrier allowing the holes to escape.

Abstract: A method of making a source-gated transistor is described, in which a gate (4) is provided on substrate (2) followed by gate insulator (6) and semiconductor layer (8). The layer is patterned to align the source with the gate (4) using photoresist (12) and back illumination through the substrate (2) with the gate (4) acting as a mask. The distance between source and drain may also be self-aligned using a spacer technique.

Abstract: In an active matrix display, each pixel has a storage capacitor for storing a voltage to be used for addressing a drive transistor. A discharge transistor is provided for discharging the storage capacitor thereby to switch off the drive transistor. The timing of this is controlled by a light-dependent device which is illuminated by the display element. The drive transistor is controlled to provide a constant light output from the display element, and the duration is controlled in dependence on the data voltage. Optical feedback is used to alter further the timing of operation of the discharge transistor to provide ageing compensation of the display element and compensation for changes in the drive transistor.

Abstract: A transistor control circuit (74) comprises a source-gated thin film transistor (70), an input for receiving a drive voltage representing a desired control of the source-gated transistor and a current source (82) for causing a known current to pass through the source-gated transistor (70). A first capacitor (78) stores a resulting gate-source voltage of the source-gated transistor when the known current is passed through the source-gated transistor The drive voltage is modified using the resulting gate-source voltage, and the modified voltage is used in the control of the source-gated transistor This control can provide a translational shift in the operating characteristics of the transistor, and it has been found that this can compensate for ageing of the transistor, for non-uniformity between different devices, and for temperature variations.

Abstract: A method of making a source-gated transistor is described, in which a gate (4) is provided on substrate (2) followed by gate insulator (6) and semiconductor layer (8). The layer is patterned to align the source with the gate (4) using photoresist (12) and back illumination through the substrate (2) with the gate (4) acting as a mask. The distance between source and drain may also be self-aligned using a spacer technique.

Abstract: A color display device based on dielectrophoresis is described. The device includes a dielectrophoretic mixture comprising semi-insulating particles of each of the subtractive primary colors cyan (32), magenta (34) and yellow (36) in a semi-insulating liquid (24). The dielectrophoretic frequency characteristics of the particles are the same or similar for particles of the same color but different between the three colors. In particular, the transition frequency (f0) is different for each color, or two colors may have the same transition frequency (f0) if one has a reversed sense dielectrophoretic frequency characteristic. Also the speeds of the particles are the same for particles of the same color but different between the three colors. The pixels are driven with alternating voltages of different frequencies (f1, f2, f3, f4) and duration determined such that different proportions of the different colors of particles are moved, dependent upon their transition frequencies and speeds.

Abstract: A matrix display has pixels 2 each including a programmable memory element 30 arranged in parallel across capacitance 28. The voltage on the capacitance controls a display element 25. The arrangement can be run in a normal mode, with all of the memory elements 30 in a high resistance state so that the matrix display can be driven dynamically. Alternatively, in a static (low power) mode of operation, the memory elements 30 are programmed with a static image which may be displayed without driving the data lines 6.

Abstract: A matrix array display device has an array of pixels on a substrate which each have a display element, such as an electroluminescent display element. An associated control circuit including a storage capacitor and a light sensing element are connected thereto for regulating charge stored on the capacitor and responsive, for example, to light emitted from the display element so as to regulate operation of the display element. The light sensing elements include thin film semiconductor devices each having a strip of semiconductor material with laterally-spaced, doped, contact regions and the associated storage capacitor is formed by a conductive layer extending substantially transversely of the strip over one contact region with intervening dielectric material. A predetermined relationship between the storage capacitor and photosensitive device characteristics is then ensured even though dimensional variations in component layers may occur due to manufacturing tolerances.

Abstract: An active matrix electroluminescent display device in which the drive current through an electroluminescent display element (20) in each pixel (10) in a drive period is controlled by a driving device (22) based on a drive signal applied during a preceding address period and stored as a voltage on an associated storage capacitor (36). In order to counteract the effects of display element ageing, through which the light output for a given drive signal level diminishes over time, the pixel includes electro-optic discharging means (40) coupled to the storage capacitor and responsive to the display element's light output to leak stored charge and to control the integrated light output of the display element in the drive period. For improved control, the discharging means is arranged to rapidly discharge the capacitor at a controlled point in the drive period, upon the drive of the display element falling to a low level. A photoresponsive transistor can conveniently be utilised for this purpose.

Abstract: An active matrix electroluminescent display device in which the drive current through an electroluminescent display element (20) in each pixel (10) in a drive period is controlled by a driving device (22) based on a drive signal applied during a preceding address period and stored as a voltage on an associated storage capacitor (36). In order to counteract the effects of display element ageing, through which the light output for a given drive signal level diminishes over time, the pixel includes electro-optic discharging means (40) coupled to the storage capacitor and responsive to the display element's light output to leak stored charge and to control the integrated light output of the display element in the drive period. For improved control, the discharging means is arranged to rapidly discharge the capacitor at a controlled point in the drive period, upon the drive of the display element falling to a low level. A photoresponsive transistor can conveniently be utilised for this purpose.

Abstract: A color display device based on dielectrophoresis is described. The device includes a dielectrophoretic mixture comprising semi-insulating particles of each of the subtractive primary colors cyan (32), magenta (34) and yellow (36) in a semi-insulating liquid (24). The dielectrophoretic frequency characteristics of the particles are the same or similar for particles of the same color but different between the three colors. In particular, the transition frequency (f0) is different for each color, or two colors may have the same transition frequency (f0) if one has a reversed sense dielectrophoretic frequency characteristic. Also the speeds of the particles are the same for particles of the same color but different between the three colors. The pixels are driven with alternating voltages of different frequencies (f1, f2, f3, f4) and duration determined such that different proportions of the different colors of particles are moved, dependent upon their transition frequencies and speeds.

Abstract: An active matrix electroluminescent display device in which the drive current through an electroluminescent display element (20) in each pixel (10) in a drive period is controlled by a driving device (22) based on a drive signal applied during a preceding address period and stored as a voltage on an associated storage capacitor (36). In order to counteract the effects of display element ageing, through which the light output for a given drive signal level diminishes over time, the pixel includes electro-optic discharging means (40) coupled to the storage capacitor and responsive to the display element's light output to leak stored charge and to control the integrated light output of the display element in the drive period. For improved control, the discharging means is arranged to rapidly discharge the capacitor at a controlled point in the drive period, upon the drive of the display element falling to a low level. A photoresponsive transistor can conveniently be utilised for this purpose.

Abstract: A matrix display has pixels 2 each including a programmable memory element 30 arranged in parallel across capacitance 28. The voltage on the capacitance controls a display element 25. The arrangement can be run in a normal mode, with all of the memory elements 30 in a high resistance state so that the matrix display can be driven dynamically. Alternatively, in a static (low power) mode of operation, the memory elements 30 are programmed with a static image which may be displayed without driving the data lines 6.

Abstract: A display device has an array of pixels comprising light emitting display elements, for example EL elements, carried on a substrate and associated light sensing elements responsive to light emitted by the display elements. The light sensing elements each comprise a gated photosensitive thin film device such as a TFT structure or a lateral gated pin device having a semiconductor layer with contact regions laterally spaced on the substrate and separated by a gate controlled region. A part of the associated display element extends over the gate controlled region with an electrode of the display element serving as the gate of the photosensitive device thereby ensuring good optical coupling between the display element and the photosensitive device and enabling the gate to be appropriately biased. Such an arrangement enables, for example, the provision of electro-optic feedback control in the pixel in comparatively simple manner.

Abstract: A thin film capacitor is provided with a thin film protection element to protect the capacitor from damage that can result due to the occurrence of an electrostatic discharge event. The thin film capacitor includes two conductive film portions forming capacitor plates and a dielectric film forming the capacitor dielectric. The protection element may take the form of a thin film diode or a series of thin film diodes connected electrically in parallel with the thin film capacitor. The whole device can be fabricated using a stoichiometric silicon nitride layer to produce the capacitor dielectric and a non-stoichiometric silicon rich silicon nitride layer to provide the diode semiconductor material. One diode is formed by one capacitor plate, the semiconductor layer and an upper diode contact.