Design of an organic pixel addressing circuit for an active-matrix OLED display

In this paper, we present a design of a flat-panel display (FPD) based on organic light-emitting diodes (OLEDs) and on organic thin-film transistors (OTFTs). Addressing mode, circuit topology, layout, and drive scheme are developed in order to reach the desired frame rate and to control the gray levels against the threshold voltage dispersions of OTFTs and OLEDs. The design shows that the current OLED and OTFT technology are suitable for FPD technology, though setting serious constraints on driver design.     

A new a-Si:H TFT pixel circuit compensating the threshold voltage shift of a-Si:H TFT and OLED for active matrix OLED

We propose a new hydrogenated amorphous silicon thin-film transistor (a-Si:H TFT) pixel circuit for an active matrix organic light-emitting diode (AMOLED) employing a voltage programming. The proposed a-Si:H TFT pixel circuit, which consists of five switching TFTs, one driving TFT, and one capacitor, successfully minimizes a decrease of OLED current caused by threshold voltage degradation of a-Si:H TFT and OLED. Our experimental results, based on the bias-temperature stress, exhibit that the output current for OLED is decreased by 7% in the proposed pixel, while it is decreased by 28% in the conventional 2-TFT pixel.     

A new a-Si:H thin-film transistor pixel circuit for active-matrix organic light-emitting diodes

We propose a new pixel circuit using hydrogenated amorphous silicon (a-Si:H) thin-film transistors (TFTs), composed of three switching and one driving TFT, for active-matrix organic light-emitting diodes (AMOLEDs) with a voltage source method. The circuit simulation results based on the measured threshold voltage shift of a-Si:H TFTs by gate-bias stress indicate that this circuit compensates for the threshold voltage shifts over 10000 h of operation.     

A novel current-scaling a-Si:H TFTs pixel electrode circuit for AM-OLEDs

Hydrogenated amorphous silicon thin-film transistor (a-Si:H TFT) pixel electrode circuit with a function of current scaling is proposed for active-matrix organic light-emitting displays (AM-OLEDs). In contrast to the conventional current mirror pixel electrode circuit, in this circuit a high data-to-organic light-emitting device (OLED) current ratio can be achieved, without increasing the a-Si:H TFT size, by using a cascade structure of storage capacitors. Moreover, the proposed circuit can compensate for the variations of TFT threshold voltage. Simulation results, based on a-Si:H TFT and OLED experimental data, showed that a data-to-OLED current ratio larger than 10 and a fast pixel programming time can be accomplished with the proposed circuit.     

Current-source a-Si:H thin-film transistor circuit for active-matrix organic light-emitting displays

In this letter, we describe a four thin-film-transistor (TFT) circuit based on hydrogenated amorphous silicon (a-Si:H) technology. This circuit can provide a constant output current level and can be automatically adjusted for TFT threshold voltage variations. The experimental results indicated that, for TFT threshold voltage shift as large as /spl sim/3 V, the output current variations can be less than 1 and 5% for high (/spl ges/0.5 /spl mu/A) and low (/spl les/0.1 /spl mu/A) current levels, respectively. This circuit can potentially be used for the active-matrix organic light-emitting displays (AM-OLEDs).     

Readout circuit for CMOS active pixel image sensor

The design and simulation results of a new readout circuit for a CMOS active pixel image sensor are presented. This scheme removes the fixed pattern noise and reduces the signal degradation while offering an increase in readout speed, compared with the conventional approach     

A new current scaling pixel circuit for AMOLED

A new active-matrix organic light-emitting diode (AMOLED) pixel design, composed of four polycrystalline silicon thin-film transistor (poly-Si TFT) and one capacitor, is proposed by employing a novel current scaling scheme. The simulation results, based on the measured characteristics of an OLED and poly-Si TFTs, show that the proposed pixel design would scale down the data current more effectively, so as to guarantee a lower charging time compared with the conventional current mirror structure, as well as successfully compensate the variation of the electrical characteristics of the poly-Si TFTs, such as the threshold voltage and mobility.     

Simulation of pixel voltage error for a-Si TFT LCD regarding thechange in LC pixel capacitance

LC pixel capacitance C_lc, which changes with the director of liquid crystal molecules as a function of external applied voltage, has a most important impact on the pixel voltage error Δ V_p and therefore on the electro-optics (E-O) characteristics of the LC pixel for an a-Si TFT LCD. In this paper, the pixel voltage error has been simulated for 10.4" VGA (640×480) and SVGA (800×600) a-Si TFT LCD, and in this simulation, we especially took into account the change in LC dielectric constant. We found that Δ V_p changes with the data voltage V_p. In addition, E-O characteristics of LC pixel for an a-Si TFT LCD has been investigated. The result shows that the effect of Δ V_p on E-O characteristics is significant when V_p ranges from the threshold voltage to the saturation voltage     

高功放高压联锁电路改进与测试

高压联锁性能的好坏直接影响设备能否正常工作。通过分析CPI高功放（HPA）的延时加高压程序、高压联锁电路和交流延时器工作原理,研究出一种新改进的高压联锁电路方案和用于交流延时器的测试方法。分析阐述表明,该方案和测试方法克服了CPI高功放的高压联锁方案的弊端。另外,根据分析结果设计了延时测试电路,它可对交流延时器性能参数进行定量测试。     

Characterization of AMOLED pixel circuit without power line

We fabricated and evaluated the simple active matrix organic light emitting diode (AMOLED) pixel circuits without power line and proved that it is useful for the AMOLED display. Without power line in the pixel circuit we got higher-aperture ratio of emission area than the pixel with power line and the pixel with high aperture ratio can give a long life time due to lower current density of organic light emitting diode. However, the lack of power line requires the verification of the driving scheme of the pixel circuit. After fabrication of two types of AMOLED with and without power line in the pixel, we evaluated the pixel currents under various conditions. The operation of the pixel circuit without power line gave similar characteristics to that of the pixel circuit with power line. By the comparison, we verified that the pixel without power line is acceptable for the application to the AMOLED display combined with feedback compensation scheme for the uniform brightness.     

In-process functional testing of pixel circuit in AM-OLEDs

This paper presents a functional testing scheme using a two-thin-film-transistor (TFT) pixel circuit of an active-matrix organic light-emitting display (AM-OLED). This pixel circuit and the co-operative electrical testing scheme can not only evaluate the characteristics of each TFT, but also determine the location of line and point defects in the TFT array. Information on defects can be used in a unique repair system that cutting and repairing these defects. Furthermore, the functional testing scheme can be applied as a part of yield management of the AM-OLED array process.     

10 /spl Omega/ 370 V high voltage switches for line circuit application

The authors describe the integration of 8 high-voltage switches together with their low-voltage polygate CMOS control logic in an 18-pin package, the HVX chip. This custom IC is intended to be used as a switching cross-point between the subscriber line and circuit equipment in digital telephony. The high-voltage DMOS is processed in a dielectrically isolated substrate, and allows the switches to have both terminals floating with respect to the low-voltage circuitry. A novel control circuit guarantees that the switch status will be defined under all circumstances.     

A new pixel circuit for active matrix organic light emitting diodes

We propose a new thin-film-transistor (TFT) pixel circuit for active-matrix organic light-emitting diode (AMOLED) composed of four TFTs and two capacitors. The simulation results, based on the device performances measured for an OLED and a poly-Si TFT, indicate that the proposed circuit has high immunity to the variation of poly-Si TFT characteristics     

磷酸处理ITO基底对有机发光二极管性能的改善

用10%、15%、20%3种浓度(体积分数)的磷酸分别对ITO玻璃进行处理,四探针测试表明其面电阻基本不变,原子力显微镜观测到酸处理后的ITO表面形貌更加平坦,紫外-可见光光谱显示出磷酸处理几乎不影响可见光透过率;以之为基底制备了典型结构(ITO/TPD/Alq/Al)有机发光二极管(OLEDs),并对其光电性能进行了测试,结果表明在经过浓度为15%的磷酸处理过的ITO玻璃上制备的OLEDs表现出最好的光电性能,其发光最大亮度和发光效率分别是未经酸处理的ITO上器件的近2倍。     

微伏级直流电压信号放大电路设计

针对微伏级直流电压信号测量过程中存在信噪比低、测量精度不高和抗干扰能力差的问题,设计一种以TLC2652为核心器件的放大测量电路,实现了对5~45μV范围内电压信号的精准放大。电路采用低通滤波电路、陷波电路降低内部噪声与外部干扰;采用隔离电路,隔离测量端对采集端的影响;采用线性稳压芯片进行电源模块的设计,提高测量精度并降低功耗。经仿真实验验证,说明所设计的微伏级直流电压信号放大电路具有抑制共模干扰、抑制温漂、稳定性好、抗干扰性强等特点,测量精度达到0.044%。     

实用电压测量电路的设计

对电压测量电路的基本要求是其应具有高输入阻抗,文章设计了几种实用的电压测量电路,即场效应管差分式电路、高阻型集成运放构成的电路、高稳定度与高增益集成运放构成的电路.这些电压测量电路具有很高的输入阻抗,因而可有效地减小测量误差,提高准确度.     

The effect of size on photodiode pinch-off voltage for small pixel CMOS image sensors

The electron potential of a photodiode in a CMOS image sensor should be designed precisely since the charge capacity of the photodiode decreases as the pixel area shrinks. The pinch-off voltage of a photodiode, which also affects the electron capacity, is dependant on the doping profile of the pn junction as well as the size of the photodiode. The pinch-off voltage is lower in a smaller photodiode. A simple method that uses the lateral depletion of a photodiode for an estimate of the pinch-off voltage in small photodiodes is proposed, and is compared to the measured experimental data. Two constants are used to account for the doping profile and photodiode size. The measurement data shows the error of the estimation of the pinch-off voltage to be <0.05 V.     

Improvement of GaN-based light-emitting diode by indium-tin-oxide transparent electrode and vertical electrode

A sapphire-etched vertical-electrode nitride semiconductor (SEVENS) light-emitting diode (LED) is fabricated by means of a selective chemical wet-etching technique. The SEVENS-LED formed on sapphire substrate exhibits excellent device performance compared to a conventional NiAu lateral-electrode (LE) GaN-based LED formed on the same sapphire substrate. The integral light-output power of SEVENS-LED is /spl sim/7 mW, which is 1.75 times stronger than that of the conventional NiAu LE-LED (/spl sim/4 mW). The external quantum efficiency of SEVENS-LED is estimated to be approximately 13%.     

旋转元件动态微电压测试电路设计

在旋转元件进行动态测试过程中,信号传输以及测试元件供电需要电线由动态旋转状态装换为静态,这样信号以及供电才能顺利实现.在为电压信号测试过程中,信号较容易受到外界干扰,信噪比较低;需要一个微型并且稳定的多通道信号放大器对信号进行放大.本文利滑环,基于AD620微型放大器设计出一个三通道微型放大器电路来实现对信号的准确采集.     

高性能PTCR电极浆料生产工艺的改进

通过增加分散剂松香的用量，提高了欧姆银浆的关键中间体材料银泥的质量稳定性。将压滤法应用于银泥洗涤工艺，既节省了设备投资，又避免了设备腐蚀。在欧姆银浆中掺入１０％的活性铝粉，降低了浆料成本，而且增强了浆料的工艺适应性。表层银浆的配制采用辊轧工艺替代球磨工艺，并对有机载体进行了调整，提高了生产效率，改善了膜层光洁度。