Search

Oxide TFTs have a negative threshold voltage (Vth), which can become even more negative in response to DC or AC stress. Therefore, these voltage stresses can cause severe leakage current in a scan driver. In this paper, a scan driver with dynamic threshold voltage control (DTVC) is proposed to minimize the leakage current and enlarge operating margin. Effectiveness of DTVC was verified with a 14-inch AMOLED.

Using available panel clam on 68 countries covering the years 1998-2006, we measure the sensitivity of per capita re-al GDP co change in each of the live social technologies by six country groups: OECD. Asia NlEs, developing countries, BRCs, less-developed countries, and Korea. The regression results suggest that each of the live social technologies in this paper (i.e., anti-corruption, deregulation, property rights, government size, and law) is positively related co per capita real GDP. The regression results also suggest that per capita real GOP is more elastic with respect to each of the five social technologies than IT as a proxy for physical technology in the group of relatively rich countries. It is evident that per capita real CDP is elastic with respect to social technologies in Korea. This implies that co speed up Korea's advancement, improving social technology may be crucial.

An on-glass integrated scan driver is proposed for oxide thin film transistors TFTs with negative threshold voltage. A coupling capacitor and a TFT for setting the initial voltage to the gate of a TFT were added to minimize the off-state current. Simulated and measured results indicate that the proposed scan driver shows no ripple and fast rise time/fall time of scan outputs. Circuit operation was verified with a 14-inch AMOLED panel.

An 8b source driver for 2.0 inch QVGA active-matrix OLEDs is fabricated using LTPS TFTs. This driver uses an 8b DAC that is separated into two parts, a 1-to-3 DEMUX, and a pre-charge method. This scheme reduces the source driver size by 40%. The maximum DNL is under 1LSB. The output voltage variation of the source driver is less than 1 LSB even though the variation of the threshold voltage is plusmn0.5V

— Large-sized active-matrix organic light-emitting diode (AMOLED) displays require high-frame-rate driving technology to achieve high-quality 3-D images. However, higher-frame-rate driving decreases the time available for compensating Vth in the pixel circuit. Therefore, a new method needs to be developed to compensate the pixel circuit in a shorter time interval. In this work, image quality of a 14-in. quarter full-high-definition (qFHD) AMOLED driven at a frame rate of over 240 Hz was investigated. It was found that image degradation is related to the time available for compensation of the driving TFT threshold voltage. To solve this problem, novel AMOLED pixel circuits for high-speed operation are proposed to compensate threshold-voltage variation at frame rates above 240 Hz. When Vth is varied over ±1.0 V, conventional pixel circuits showed current deviations of 22.8 and 39.8% at 240 and 480 Hz, respectively, while the new pixel circuits showed deviations of only 2.6 and 5.4%.

— Amorphous-oxide thin-film-transistor (TFT) arrays have been developed as TFT backplanes for large-sized active-matrix organic light-emitting-diode (AMOLED) displays. An amorphous-IGZO (indium gallium zinc oxide) bottom-gate TFT with an etch-stop layer (ESL) delivered excel lent electrical performance with a field-effect mobility of 21 cm2/V-sec, an on/off ratio of >108, and a subthreshold slope (SS) of 0.29 V/dec. Also, a new pixel circuit for AMOLED displays based on amorphous-oxide semiconductor TFTs is proposed. The circuit consists of four switching TFTs and one driving TFT. The circuit simulation results showed that the new pixel circuit has better performance than conventional threshold-voltage (VTH) compensation pixel circuits, especially in the negative state. A full-color 19-in. AMOLED display with the new pixel circuit was fabricated, and the pixel circuit operation was verified in a 19-in. AMOLED display. The AMOLED display with a-IGZO TFT array is promising for large-sized TV because a-IGZO TFTs can provide a large-sized backplane with excellent uniformity and device reliability.

An active matrix organic light emitting diode pixel circuit and its driving scheme for high frame frequency are proposed for implementation of a 3D display. The proposed pixel circuit can compensate the threshold voltage distribution of low temperature poly silicon-thin film transistors at high-speed operation of 240Hz or more. According to the simulation, current deviation of 1.73% and 3.94% are obtained at frame rates of 240Hz and 480Hz when Vth distribution is ±0.5 V.

Amorphous oxide thin film transistor (TFT) arrays have been developed as TFT backplanes for large size active-matrix organic light emitting diode (AMOLED) displays. An amorphous IGZO (Indium Gallium Zinc Oxide) bottom gate TFT with an etch-stop layer (ESL) delivered excellent electrical performance with field- effect mobility of 21 cm2/V-s, an on/off ratio of >108, and subthreshold slope (SS) of 0.29V/dec. A full color 19-inch AMOLED display has been developed using the amorphous IGZO TFT backplane.

With an excimer laser annealing (ELA) process, maximum display size is limited by the laser beam length because performance variations of the transistors in the overlapped regions cannot be sufficiently compensated to remove the brightness non-uniformity. In this paper, a redundant pixel line design is proposed to remove overlap mura. A 4.82″ AMOLED was successfully fabricated in order to verify the panel design method.