Abstract: Methods and apparatus for measuring current are provided. In one arrangement, a first charge amplifier integrates a current to be measured. A processing circuit filters an output from the first charge amplifier using a first low pass filter module and a second low pass filter module. A second charge amplifier integrates a current derived from the filtered output from the first charge amplifier. The apparatus is configured to reset the first charge amplifier at the start of each of a plurality of sensing frames. The processing circuit obtains at least a first sample of the output from the first charge amplifier in each sensing frame. The sampling of the first sample alternates from one sensing frame to the next sensing frame between sampling via the first low pass filter module and sampling via the second low pass filter module.

Abstract: Methods and apparatus for measuring current are provided. In one arrangement, a first charge amplifier integrates a current to be measured. A processing circuit filters an output from the first charge amplifier using a first low pass filter module and a second low pass filter module. A second charge amplifier integrates a current derived from the filtered output from the first charge amplifier. The apparatus is configured to reset the first charge amplifier at the start of each of a plurality of sensing frames. The processing circuit obtains at least a first sample of the output from the first charge amplifier in each sensing frame. The sampling of the first sample alternates from one sensing frame to the next sensing frame between sampling via the first low pass filter module and sampling via the second low pass filter module.

Abstract: Methods and apparatus for measuring current are provided. In one arrangement, a first charge amplifier integrates a current to be measured. A processing circuit filters an output from the first charge amplifier using a first low pass filter module and a second low pass filter module. A second charge amplifier integrates a current derived from the filtered output from the first charge amplifier. The apparatus is configured to reset the first charge amplifier at the start of each of a plurality of sensing frames. The processing circuit obtains at least a first sample of the output from the first charge amplifier in each sensing frame. The sampling of the first sample alternates from one sensing frame to the next sensing frame between sampling via the first low pass filter module and sampling via the second low pass filter module.

Abstract: Arrangements are disclosed for measuring small electrical currents with high sensitivity, for example in the context of sensing molecular entities, for example via interactions between the molecular entities and a membrane protein inserted in an amphiphilic membrane. In one arrangement there is provided a current sensing circuit (52) configured to integrate the current output by a sensor element (56) during each of a plurality of sensing frames (62). In each sensing frame (62) first and second analogue samples of the integral are taken during first and second time windows (71,72). A readout circuit (54) processes the first and second analogue samples to output a digital output signal representing the current output by the sensor element (56). The processing comprises analogue to digital conversion processing and output processing. The output processing is performed exclusively during periods outside of the first and second time windows.

Abstract: Arrangements are disclosed for measuring small electrical currents with high sensitivity, for example in the context of sensing molecular entities, for example via interactions between the molecular entities and a membrane protein inserted in an amphiphilic membrane. In one arrangement there is provided a current sensing circuit (52) configured to integrate the current output by a sensor element (56) during each of a plurality of sensing frames (62). In each sensing frame (62) first and second analogue samples of the integral are taken during first and second time windows (71,72). A readout circuit (54) processes the first and second analogue samples to output a digital output signal representing the current output by the sensor element (56). The processing comprises analogue to digital conversion processing and output processing. The output processing is performed exclusively during periods outside of the first and second time windows.

Abstract: An active matrix LED display has a light-dependent device for detecting the brightness of the display element and threshold voltage measurement circuitry for measuring a threshold voltage of a pixel the drive transistor. Compensation for ageing of the display element is thus provided by an optical feedback path, and compensation for drive transistor threshold variations is provided by measurement of the threshold voltage. This provides a reliable compensation scheme for the threshold voltage variations, while also providing ageing compensation.

Abstract: A method is provided of determining the pixel drive signals to be applied to the pixels of an array of light emitting display elements arranged in rows and columns, with a plurality of the pixels in a row being supplied with current simultaneously along a respective row conductor. Target pixel drive currents are determined from a model of the pixel current-brightness characteristics. These are modified to take account of the voltage on the respective row conductor at each pixel resulting from the currents drawn from the row conductor by the plurality of pixels and the dependency of the pixel brightness characteristics on the voltage on the row conductor at the pixel. This addresses the problem of horizontal cross-talk that occurs in active matrix LED displays due to the finite output impedance of the current providing TFTs as well as the finite resistance of metals used to form power supply lines.

Abstract: An active matrix electroluminescent display device has pixels using an amorphous silicon or microcrystalline silicon drive NMOS transistor (22) connected between the anode of the display element (2) and a power supply line (26). A storage capacitor (24) is connected between the anode of the display element and the gate of the drive transistor (22). An amorphous silicon or microcrystalline silicon second drive NMOS transistor (30) supplies a holding voltage to the anode of the display element (2). This arrangement enables the voltage across the display element to be held while the transistor gate drive voltage is stored on the storage capacitor. This enables an accurate current source pixel circuit to be implemented using NMOS transistors.

Abstract: In an active matrix electroluminescent display device, comprising an array of display pixels, each pixel comprises an electroluminescent display element, active matrix circuitry including at least one drive transistor for driving a current through the display element, means for determining an overall brightness level of an image to be displayed in a frame period, means for controlling the at least one drive transistor of each pixel in dependence on, (1) a respective input signal providing a drive level for the pixel, and (2) the overall brightness level. The novel arrangement is capable of controlling the pixels to limit the maximum currents drawn by the pixels, thereby limiting cross-talk effects resulting from voltage drops along row or column conductors. If an image is bright, the pixel drive levels across the image, or at least part of the image, can be reduced, so that the maximum brightness is reduced.

Abstract: An active matrix display panel comprises a substrate, an array of pixel circuits being arranged in a matrix of at least one column and a plurality of rows on the substrate, each pixel circuit comprising a light-emitting element, capable of emitting light of an intensity determined by the value of a current passed through it, and at least one column line, each column line arranged to conduct a reference current, provided by a current driving circuit, when connected to the panel. The pixel circuits in a column are divided into a plurality of groups of at least one pixel circuit. The active matrix display panel comprises at least one current mirror circuit associated with a first group, comprising a first current mirror, arranged to mirror a reference current flowing through a column line to a first current mirror output.

Abstract: An active matrix display device has an array of display pixels, each pixel comprising a current-driven light emitting display element (2), a drive transistor (22) for driving a current through the display element and pixel circuitry including an optical feedback element (38) for controlling the drive transistor to drive a substantially constant current through the display element for a duration which depends on the desired display pixel output level and an optical feedback signal of the optical feedback element. An output configuration is applied to the display which includes values for the pixel power supply voltages, the field period and an allowed range of pixel drive levels. The output configuration is varied in response to ageing of the display element. In this device, an output configuration is varied as the device ages, so that the optical feedback system can continue to provide compensation for differential ageing of the display elements for a longer period of use of the display.

Abstract: An active matrix display device comprises an array of display pixels, with each pixel comprising an EL display element, a light-dependent device for detecting the brightness of the display element and a drive transistor circuit for driving a current through the display element. The drive transistor is controlled in response to the light-dependent device output so that ageing compensation can be implemented. The light-dependent device is located laterally of the area of light emitting material of the EL display element. In this way, the light-dependent device does not cause step coverage problems and can be integrated into the pixel layout without affecting the pixel aperture. Furthermore, the light dependent device can extend alongside the full length of the area of light emitting material so that it receives light input from a large part of the display element area.

Abstract: An active matrix display device stores a transistor drive voltage on a storage capacitor (24; Cs). A light-dependent device (27) effects discharge of the storage capacitor in dependence on the light output of the light emitting display element (2). Power is provided to each pixel from a first power line (26), and one of the light dependent device and the storage capacitor is coupled to a second power supply line (50), to which a varying voltage is provided during a pixel illumination period. By varying the voltage on one of the power supply lines, the discharge characteristics of the capacitor by the optical feedback system are altered to provide compensation for the light-dependent device leakage currents.

Abstract: Each pixel of an active matrix electroluminescent display device has a first amorphous silicon drive transistor for intermittently driving a current through the display element and a second amorphous silicon drive transistor for intermittently driving a current through the display element. The aging effect of amorphous silicon TFTs can be reduced by sharing the driving of the display element between two drive transistors. Providing a duty cycle reduces the on-time for each drive transistor, but also provides a period during which there can be some recovery of the TFT characteristics.

Abstract: A method of manufacturing a color active matrix display device comprises forming islands over a rigid carrier substrate, forming a plastic substrate over the rigid carrier substrate, forming an array of pixel circuits over the plastic substrate and forming a display layer over the array of pixel circuits. The rigid carrier substrate is then released from the plastic substrate and the plastic substrate then has channels defined by the islands. These are filled to define color filter portions. The formation of a plastic substrate on a rigid carrier, with the use of a subsequent lift off process, enables the circuit arrays to be made on very thin plastic sheets. The color filters can then be made on the outside of the LC cell. Depressions are formed in the plastic substrate registered to the circuit array, and these are filled in with color filter material, for example by ink jet printing.

Abstract: An electroluminescent (EL) display device has current-driven pixels and is operable in at least two phases within each frame period. In one phase, one of a first plurality (31) of analogue drive currents can be driven through EL display element. In another longer phase, one of a second plurality (33) of analogue drive currents is independently driven through the EL display element. This device combines a time ratio method with an analogue drive scheme. A shorter phase may provide the higher resolution (smaller) increments and one longer phase may provide lower resolution (larger) increments. Low brightness outputs can be achieved with a higher drive current, but over a short duration, which reduces non-uniformity in the pixel output.

Abstract: An active matrix display panel comprises a substrate, an array of pixel circuits being arranged in a matrix of at least one column and a plurality of rows on the substrate, each pixel circuit comprising a light-emitting element, capable of emitting light of an intensity determined by the value of a current passed through it, and at least one column line, each column line arranged to conduct a reference current, provided by a current driving circuit, when connected to the panel. The pixel circuits in a column are divided into a plurality of groups of at least one pixel circuit. The active matrix display panel comprises at least one current mirror circuit associated with a first group, comprising a first current mirror, arranged to mirror a reference current flowing through a column line to a first current mirror output.

Abstract: An active matrix electroluminescent display has means for interrupting the drive of current through the display element. Row driver circuitry for the display has a shift register and logic arrangement (50, 54) for generating the drive voltage for the interrupting means, and which includes a pulse having a duration which can be varied up to substantially the full field period less the address period. The signal or signals propagated through the shift register arrangement (50) control the pulse duration. This arrangement provides reduced driver complexity to allow control for the row by row addressing of the pixels with control of the overall light emission period of each row. The control enables a scrolling addressing scheme to be implemented.

Abstract: The pixels of an active matrix display device have a current-driven light emitting display element, a drive transistor for driving a current through the display element, a storage capacitor for storing a pixel drive voltage to be used for addressing the drive transistor, a light-dependent device for detecting the brightness of the display element, and driver circuitry for providing data signals to the pixel external to the pixel array. This provides a pixel with optical feedback to compensate for display element ageing. The driver circuitry has a processing means for processing the feedback brightness signals and derives from them a threshold voltage for the drive transistor of the pixel as well as information relating to the performance of the display element, for ageing compensation.

Abstract: In an active matrix electroluminescent display device, an overall brightness level of an image to be displayed in a frame period is determined. A drive transistor of each pixel is controlled in dependence on an input drive signal for the pixel and on the overall brightness level, for example using a signal processor (30) to vary the pixel drive signals. This arrangement can control the pixels to limit the maximum currents drawn by the pixels, thereby limiting the cross talk effects resulting from voltage drops along row or column conductors. If an image is bright, the pixel drive levels across the image (or at least a part of the image) can be reduced, so that the maximum brightness is reduced.