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: An active matrix electroluminescent display device uses a stepped voltage waveform to the input of the pixel, the stepped voltage waveform being voltage-shifted by a previously stored pixel drive voltage before application to the gate of a drive transistor. The level of the voltage shift determines the duty cycle with which the display element is driven, and thereby controls the grey level output. The height of the steps in the stepped voltage waveform is greater than the voltage width of linear operating region of the drive transistor, so that a selected step of the stepped waveform defines a transition from the drive transistor between fully on and fully off. In this way, the drive transistor is never driven in the linear region.

Abstract: An active matrix electroluminescent display device comprises an array of display pixels. In each pixel, a first switch connects power from a power supply line to the display element and a second switch routes current from a current-measurement supply line to the display element. The gate voltage applied to a drive transistor is controlled by a feedback system, such that control voltage is controlled in closed loop manner to achieve the desired current. The control voltage can then be used for subsequent addressing of the pixel.

Abstract: An active matrix electroluminescent display device has a current sampling resistor within each pixel in series with the display element. A feedback signal represents the voltage drop across the current sampling resistor and the pixel drive signals are modified in dependence on the feedback signal to control the current driven through the display element. In this way, threshold compensation is provided, whilst enabling a single voltage-driven drive transistor to be employed.

Abstract: Driver circuitry of each pixel provides pixel drive currents to respective LED display elements of the pixels of a display. An output transistor arrangement for each column drive circuit within a pixel has a plurality of output transistors (70, 72, 74) in parallel, and one or more of these are selected in order to provide desired output characteristics. Thus, the output of each column drive circuit can be tuned to provide desired output characteristics. In order to select an output transistor, fusible links of non selected transistors may be broken, or further transistors may connect selected transistors to a gate control line while non-selected transistors are connected to a de-select line.

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: An active matrix electroluminescent display device has a current sampling resistor within each pixel in series with the display element. A feedback signal represents the voltage drop across the current sampling resistor and the pixel drive signals are modified in dependence on the feedback signal to control the current driven through the display element. In this way, threshold compensation is provided, whilst enabling a single voltage-driven drive transistor to be employed.

Abstract: An active matrix electroluminescent display device uses a stepped voltage waveform to the input of the pixel, the stepped voltage waveform being voltage-shifted by a previously stored pixel drive voltage before application to the gate of a drive transistor. The level of the voltage shift determines the duty cycle with which the display element is driven, and thereby controls the grey level output. The than the voltage width of linear operating region of the drive transistor, so that a selected step of the stepped waveform defines a transition from the drive transistor between fully on and fully off. In this way, the drive transistor is never driven in the linear region.

Abstract: An active matrix electroluminescent display device comprises an array of display pixels. In each pixel, a first switch connects power from a power supply line to the display element and a second switch routes current from a current-measurement supply line to the display element. The gate voltage applied to a drive transistor is controlled by a feedback system, such that control voltage is controlled in closed loop manner to achieve the desired current. The control voltage can then be used for subsequent addressing of the pixel.

Abstract: A zero result detector for detecting a zero result in the sum of a first operand A, a second operand B and a carry bit Cin operates by calculating {overscore (A)} and {overscore (A)}+1 and then comparing one of these with B (Cin=O, {overscore (A)}; Cin=1, {overscore (A)}+1) in dependence upon Cin. If the comparison shows equality, then the zero detect result Z is true.