Abstract: A digital to analogue converter includes at least one capacitor for storing an analogue output voltage resulting from the digital to analogue conversion. The converter further includes an output switch arrangement coupling the at least one capacitor to an output of the converter. The output switch arrangement is operated a plurality of times for each digital to analogue conversion, so that the analogue output voltage is switched to the output of the converter a plurality of times for each digital to analogue conversion. Each switching operation reduces the influence of an output load capacitance on the output signal. As a result smaller components can be used in the converter to achieve a given output signal resolution.

Abstract: A large-area electronic device, such as an AMLCD, has switching TFTs (T.sub.p) in a matrix and circuit TFTs (T.sub.s) in a peripheral drive circuit. Both the TFTs (T.sub.p, T.sub.s) comprise a field-relief region (130) which has a lower doping concentration (N-) than their drain region (113) and which is present between their channel region (111) and the drain region (113). This field-relief region (130), at least over most of its length, overlaps with the gate (121) in the circuit TFTs (T.sub.s) so as to reduce series resistance in the field-relief region (130) by conductivity modulation with the gate (121). However, the drain region (113) in the switching TFTs (T.sub.p) is offset from overlap with their gate (121) by at least most of the length of their field-relief region (130). This field-relief offset permits the switching TFTs (T.sub.p) to have a lower leakage current than the circuit TFTs (T.sub.s).

Abstract: A matrix display device having an array of picture elements (12) which each comprise a serial charge redistribution D to A converter circuit that includes two transistors (30, 31) and two capacitors (34, 35), at least one of which comprises an electro-optic, e.g. liquid crystal, display element, and which are driven by switching signals and digital data signals from a drive circuit (21, 25) via row and column address conductors (18, 19) respectively. The two transistors of a picture element are of complementary type, e.g. n and p TFTs, connected to the same row conductor and operable in sequence by the switching signal on the row conductor (18). The drive circuit (21) is consequently simplified and the vertical scan direction can readily be reversed.

Abstract: In an LCD or other electronic device, thin-film circuit elements on a substrate (100) form a sample-and-hold or other sampling circuit (10). The circuit (10) comprises a TFT (Ts) as a sampling transistor and preferably another TFT (T2) to compensate for displacement currents in charging and discharging the insulated gate (12) of the sampling TFT. Even when T2 is included, a slow drift in output voltage (Vo) is observed when Ts switches off, and this limits use of the circuit, especially in large area active-matrix devices. In accordance with the invention this slow drift is removed or significantly reduced by injecting minority carriers into the channel region of Ts (and T2) from a doped opposite-type region (119) or Schottky contact region (119) which is forward biased via a thin-film supply line (129). The minority carriers neutralise majority carriers which are being slowly released by thermal emission from trapping states in the TFT body.

Abstract: A shift register or other electronic drive circuit, for an LCD or other active matrix device includes a series of circuit blocks each having redundancy in the form of parallel circuit paths. When the circuit is turned on, self-testing and redundancy selection is carried out by individual test and control arrangements which are associated with the circuit blocks. The test and control arrangements may comprise memory elements, such as a bistable, which electrically program themselves in response to their electrical testing of the circuit paths so as to generate a control signal at an output coupled to one or more output switches. The output switches control which of the parallel circuit paths provides an output to the active matrix device. Each test and control arrangement also comprises a routing circuit controlled by the control signal, for transmitting the correct serial output of that circuit to all serial inputs of a next circuit block.

Abstract: Thin-film circuits comprising e.g. TFTs have inferior performance as compared with monolithic integrated circuits, and this inferior performance limits their use for e.g. drive circuits in large-area electronic devices such as an active matrix liquid-crystal display. In accordance with the invention, feedback with an external amplifier (150) is used to enhance the performance of a thin-film circuit. The feedback is taken from parallel nodes (40) of sequential stages (T1) of the circuit so that a common feedback line (51) and common external amplifier (150) can be used, thus reducing the number of substrate terminals and external connections required. Various buffers may be included between the feedback line (51) and the feedback terminal (56) to reduce the capacitive load on the line (51).

Abstract: An active matrix display device having an array of picture elements (12) comprising capacitive display elements, for example, liquid crystal elements, driven by row and column drive circuits (21,25) via row and column conductors (18,19) in which the column drive circuit (25) supplies multi-bit digital data signals to the column conductors (19) and in which each picture element is configured as a serial charge redistribution digital to analogue converter circuit for providing the analogue voltage required by the display element. The converter circuit can comprise two switching devices (T1,T2), e.g. TFTs, and two capacitors obtained by dividing the display element into two sub-elements (CP1,CP2). Row conductors (18) may be shared between adjacent rows of picture elements.

Abstract: A matrix display device comprises a row and column array of picture elements (12) each of which consists of a display element (14), e.g. a LC display element, connected in series with a two-terminal non-linear device 15, such as a MIM, between associated row and column address conductors (16,17) to which selection and data signals are applied by a scanning signal drive circuit (20) and a data signal drive circuit (22) respectively, and a reference element circuit (34), comprising a non-linear device (35) in series with a capacitor (36), forming part of a feedback arrangement through which picture element drive voltages are controlled (25) so as to compensate for the effects of aging of the non-linear devices. The reference circuit is driven like the picture elements, with a scanning signal waveform and voltage signal (V.sub.A) applied to opposite sides, and the picture element drive voltages are adjusted in accordance with predetermined changes in the voltage across the capacitor (36).

Abstract: A matrix liquid crystal display device of the kind having a light shielding matrix (18) in the form of a grid of electrically conductive material carried on the same plate (11) as one set of address conductors (20) and separated therefrom by an insulating layer (21), further includes a conductive band (30) which extends around and contacts the periphery of the grid (18) and exhibits less resistance per unit length than the portions (19) of conductive material constituting the grid, and which is connected at a plurality of points to a predetermined potential, e.g. ground, whereby cross-talk effects due to capacitive couplings between the matrix and the address conductors are reduced.

Abstract: A matrix liquid crystal display device of the kind having a light shielding matrix (18) in the form of a grid of electrically conductive material carried on the same plate (11) as one set of address conductors (20) and separated therefrom by an insulating layer (21), further includes a feedback circuit arrangement, comprising for example a high gain differential amplifier (40), connected to the matrix which is responsive to voltages on the matrix to apply a correcting voltage tending to maintain the matrix at a predetermined potential, e.g. ground, whereby cross-talk effects due to capacitive couplings between the matrix and the address conductors are reduced.

Abstract: The image sensor (1a) has a transparent substrate (2) supporting a two dimensional array (3) of photosensitive and switching elements (4) with switching signal conductors (5) and data signal conductors (6) connected to the photosensitive and switching elements (4) for enabling individual photosensitive elements to be accessed. The photosensitive and switching elements (4) and the conductors (5 and 6) are arranged such that at least half of the area of the image sensor is transparent during operation. Each photosensitive element is electrically coupled to a respective capacitor (7) for storing charge generated as a result of light being incident on the photosensitive element. The capacitors (7) are formed so as to be transparent and so as to occupy a significant part of the entire area of the array (3).

Abstract: In a matrix display apparatus for displaying video signal of two or more different standards, such as PAL and NTSC standards comprising a display panel (10), for example, a liquid crystal display panel, having a row and column array of picture elements (12), a column driver circuit (22) for sampling lines of an applied video signal (25) and supplying data signals to the panel (10), a row driver circuit (20) for scanning the rows of picture elements in turn, and a control circuit (21) controlling the timing of the operations of the row and column driver circuits (20,22), the row driver circuit (20) is controlled by signals ST,CLK so as to scan the rows of picture elements at a rate which is a function of the number of rows in the panel (10) and the field period of the applied video signal.

Abstract: A touch sensor array system includes a row and column array of individual sensing elements each of which has a bistable circuit arranged to adopt one of the other of its two stable state in dependence upon whether or not a touch input, by e.g. a stylus or finger, exists at the sensing element location. The rows of sensing elements are periodically reset in sequence by a scanning address circuit and the states of their bistable circuits are determined at regular intervals related to resetting by a detection circuit using active matrix addressing of the sensing elements. Each sensing element includes a switching device. The array of sensing elements is fabricated using thin film, e.g. TFT, technology so that high resolution is possible. The system can be used as an overlay to a display device, e.g. a matrix liquid crystal display device.