Abstract:
A technique for suppressing affect of irregularities of transistor characteristics in a signal line drive circuit. The signal line drive circuit includes a first current source circuit 437 and a second current source circuit 438, each having capacity means and supply means. According to a sampling pulse supplied from a shift register 418 and a latch pulse supplied from outside, the capacity means converts the total of currents supplied from n video signal constant current sources 109 into a voltage. The supply means supplies current based on the converted voltage. Thus, current output is performed according to a video signal, not depending on the transistor characteristics. The current values supplied from the n video signal constant current sources are set to 20, 21, ..., 2n, thereby enabling expression of gradation.
Abstract:
An active matrix electroluminescent display device has an array of current-driven electroluminescent display elements (10), for example comprising organic electroluminescent material, whose operations are each controlled by an associated switching means (10) to which a drive signal for determining a desired light output is supplied in a respective address period and which is arranged to drive the display element according to the drive signal following the address period. Each switching means comprises a current mirror circuit (30, 32, 38) in which the same transistor (30) is used to both sense and produce the required drive current for the display element (20) with the gate of the transistor being connected to a storage capacitance (30) on which a voltage determined by the drive signal is stored. This allows variations in transistor characteristics over the array to be compensated and improved uniformity of light outputs from the display elements to be obtained.
Abstract:
An active matrix display device is disclosed. The display includes individual driver circuits for each pixel (100) to provide accurate, high resolution gray scale rendering and an almost 100 % duty cycle. The pixel circuit drivers (Figures 1(10), 2(20), 3(30), 4(40), 5(50), 6(60), 7(70) and 8(80)) minimize factors known to limit gray scale resolution, such as variations in threshold voltage, voltage drops in connecting lines and from leakage currents, and large peak currents. The present invention includes a line driver functioning initially as a low impedance voltage driver (Figure 6(60)), then converting to a high impedance current driver (Figure 6(60)). A method of driving a pixel (100) with sufficient circuitry to substain the pixel's light output at a gray level determined by the input data fed to the pixel (100) is also disclosed. The display is capable of processing both digital and anolog input data.