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1.
Amorphous silicon thin film transistor circuit integration for organic LED displays on glass and plastic 总被引:2,自引:0,他引:2
Nathan A. Kumar A. Sakariya K. Servati P. Sambandan S. Striakhilev D. 《Solid-State Circuits, IEEE Journal of》2004,39(9):1477-1486
This paper presents design considerations along with measurement results pertinent to hydrogenated amorphous silicon (a-Si:H) thin film transistor (TFT) drive circuits for active matrix organic light emitting diode (AMOLED) displays. We describe both pixel architectures and TFT circuit topologies that are amenable for vertically integrated, high aperture ratio pixels. Here, the OLED layer is integrated directly above the TFT circuit layer, to provide an active pixel area that is at least 90% of the total pixel area with an aperture ratio that remains virtually independent of scaling. Both voltage-programmed and current-programmed drive circuits are considered. The latter provides compensation for shifts in device characteristics due to metastable shifts in the threshold voltage of the TFT. Various drive circuits on glass and plastic were fabricated and tested. Integration of on-panel gate drivers is also discussed where we present the architecture of an a-Si:H based gate de-multiplexer that is threshold voltage shift invariant. In addition, a programmable current mirror with good linearity and stability is presented. Programmable current sources are an essential requirement in the design of source driver output stages. 相似文献
2.
Device and circuit level optimization for high performance a-Si:H TFT-based AMOLED displays 总被引:1,自引:0,他引:1
Active matrix organic light-emitting diode (AMOLED) displays with amorphous hydrogenated silicon (a-Si:H) thin-film transistor (TFT) backplanes are becoming the state of art in display technology. Though a-Si:H TFTs suffer from an intrinsic device instability, which inturn leads to an instability in pixel brightness, there have been many pixel driving methods that have been introduced to counter this. However, there are issues with these circuits which limit their applicability in terms of speed and resolution. This paper highlights these issues and provides detailed design considerations for the choice of pixel driver circuits in general. In particular, we discuss the circuit and device level optimization of the pixel driver circuit in a-Si:H TFT AMOLED, displays for high gray scale accuracy, subject to constraints of power consumption, and temporal and spatial resolution. 相似文献
3.
Striakhilev D. Nathan A. Vygranenko Y. Servati P. Lee C.-H. Sazonov A. 《Display Technology, Journal of》2006,2(4):364-371
Amorphous silicon (a-Si) thin-film transistor (TFT) backplanes are very promising for active-matrix organic light-emitting diode displays (AMOLEDs) on plastic. The technology benefits from a large manufacturing base, simple fabrication process, and low production cost. The concern lies in the instability of the TFTs threshold voltage (VT) and its low device mobility. Although VT-instability can be compensated by means of advanced multi-transistor pixel circuits, the lifetime of the display is still dependent on the TFT process quality and bias conditions. A-Si TFTs with field-effect mobility of 1.1 cm2/Vmiddots and pixel driver circuits have been fabricated on plastic substrates at 150 degC. The circuits are characterized in terms of current drive capability and long-term stability of operation. The results demonstrate sufficient and stable current delivery and the ability of the backplane on plastic to meet AMOLED requirements 相似文献
4.
Sakariya K. Ng C.K.M. Servati P. Nathan A. 《Electron Devices, IEEE Transactions on》2005,52(12):2577-2583
Electronics reliability testing is traditionally carried out by accelerating the failure mechanisms using high temperature and high stress, and then predicting the real-life performance with the Arrhenius model. Such methods have also been applied to organic light-emitting diode (OLED) testing to predict lifetimes of tens of thousands of hours. However, testing the active matrix OLED thin-film transistor (TFT) backplane is a unique and complex case where standard accelerated testing cannot be directly applied. This is because the failure mechanism of pixel circuits is governed by multiple material and device effects, which are compounded by the self-compensating nature of the circuits. In this paper, we define and characterize the factors affecting the primary failure mechanism and develop a general method for accelerated stress testing of TFT pixel circuits in a-Si AMOLED displays. The acceleration factors derived are based on high electrical and temperature stress, and can be used to significantly reduce the testing time required to guarantee a 30 000-h display backplane lifespan. 相似文献
5.
6.
有机发光二极管显示器(OLED)正越来越多地用于中小尺寸的显示,但在大尺寸方面进展缓慢,因为在有源大尺寸方面对OLED的稳定性和均匀性要求较高,需要设计像素补偿电路。各研究机构提出了像素补偿电路用于改善OLED的均匀性和稳定性等问题,文中对目前采用有源OLED的α-Si TFT和p-Si TFT的各种像素补偿电路进行了分析。分析结果表明,文中设计方案取得了一定的效果,但尚存不足。 相似文献
7.
《Electron Device Letters, IEEE》2009,30(4):377-379
8.
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 相似文献
9.
A new a-Si:H TFT pixel circuit compensating the threshold voltage shift of a-Si:H TFT and OLED for active matrix OLED 总被引:1,自引:0,他引:1
Jae-Hoon Lee Ji-Hoon Kim Min-Koo Han 《Electron Device Letters, IEEE》2005,26(12):897-899
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. 相似文献
10.
《Microelectronics Journal》2015,46(10):923-927
In this paper, pixel circuit using mirroring structure with Indium–Gallium–Zinc oxide (IGZO) thin film transistors (TFTs) for active matrix organic light emitting diode (AMOLED) display is proposed. This pixel circuit consists of only four TFTs, and one capacitor. Due to the mirroring structure, characteristic of the driving TFT can be precisely sensed by the sensing TFT, which is deployed in a discharging path for gate electrode of the driving TFT. This discharging process is strongly dependent on threshold voltage (VT) and effective mobility of the sensing TFT. Circuit operating details are discussed, and compensation effects for threshold voltage shift and mobility variations are verified through numerical derivation and SPICE simulations. Furthermore, compared with conventional schematics, the proposed pixel circuit might have much simplified external driving circuits, and it is a promising alternative solution of high performance AMOLED display. 相似文献
11.
A field-effect thin-film transistor (TFT) with two gates, which are charge and voltage gates, is introduced. By applying a proper voltage to the voltage gate, the device is biased at a desired operating point or turned on and off, whereas the amount of charge deposited on the charge gate, which is embedded inside the dielectric, shifts the threshold voltage and therefore modulates the drain-source current. Such device finds application in sensor circuits, particularly high resolution sensor arrays, where it replaces both the transconducting amplifier and the addressing switch transistor, thus reducing transistor count per pixel. Device structure, operation, and characteristics are derived and discussed. A planar configuration of the charge-gated TFT was fabricated by using top-gate amorphous silicon TFTs and implemented in a 100-mum -pitch two-transistor active pixel sensor test structure. 相似文献
12.
A New Poly-Si TFT Current-Mirror Pixel for Active Matrix Organic Light Emitting Diode 总被引:1,自引:0,他引:1
《Electron Device Letters, IEEE》2006,27(10):830-833
A new poly-Si thin-film-transistor (TFT) current-mirror-active-matrix-organic-light-emitting-diode (AMOLED) pixel, which successfully compensates for the variation of the threshold voltage as well as mobility in the excimer laser annealed poly-Si TFT pixel, is designed and fabricated. The OLED current$(I_ OLED)$ of the proposed pixel does not depend on the operating temperature. When the temperature of pixel is increased from 27$^circhboxC$ to 60$^circhboxC$ , the$I_ OLED$ of the new pixel circuit composed of four TFTs and one capacitor increases only about 1.5%, while that of a conventional pixel composed of two TFTs and one capacitor increases about 37%. At room temperature, nonuniformity of the$I_ OLED$ in the proposed circuit was also considerably suppressed at around 9%. We have successfully fabricated a 1.2-in AMOLED panel$(hbox96 times hbox96 times hboxred green blue)$ to evaluate the performance of the proposed pixel. A troublesome residual image caused by the hysteresis phenomenon of the poly-Si TFT was almost eliminated in the proposed AMOLED panel as a result of current programming. 相似文献
13.
Active-matrix organic light-emitting-diode (AMOLED) displays based on amorphous hydrogenated silicon (a-Si:H) thin-film transistors (TFTs) are the state of the art in display technology, owing to the feasilibility of low-cost fabrication and accessability to well-established TFT-LCD fabrication. While the a-Si:H TFT offers excellent matching of device properties over large areas, it suffers from a gate-bias-dependent threshold voltage shift in time, leading to grayscale inaccuracies. In order to counter this problem, many compensation circuits have been designed. The purpose of the compensation circuit is to estimate the threshold voltage shift in driver TFTs and apply a correction so as to maintain a constant brightness. However, all of the compensation circuits designed to date suffer from low spatial and temporal resolution and reliability issues or high cost due to the use of custom-made CMOS technology. In this paper, we focus on building AMOLED display systems solely based on a-Si:H TFT technology along with the use of off-the-shelf CMOS components to lower costs. Furthermore, we achieve high spatial and temporal resolution and high yield with the use of a two-TFT voltage programmed pixel circuit along with a statistical based external calibration circuit. 相似文献
14.
Jae-Hoon Lee Woo-Jin Nam Sang-Hoon Jung Min-Koo Han 《Electron Device Letters, IEEE》2004,25(5):280-282
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. 相似文献
15.
Recent advances in organic light emitting diode (OLED) device efficiencies are making the amorphous silicon (a-Si) backplane a viable solution for a large range of display sizes. This paper presents the possibilities and design challenges of a-Si active-matrix organic light-emitting-diode (AMOLED) backplanes for applications ranging from small full color cell phone displays to HDTV screens. An analytical model for the minimum pixel-area, and hence the maximum resolution for both bottom and top emitting AMOLED architectures is presented in terms of the a-Si thin-film transistor (TFT) device parameters, the process design-rules, and the pixel circuit parameters. It is established that the lower device mobility of a-Si TFTs is no longer the limiting factor. For instance, in a 20' W/SXGA panel with full color red-green-blue subpixels, the state-of-the-art TFT processes yield a square pixel size of /spl sim/266 /spl mu/m. Further, quantitative analysis of charge-injection/charge-feedthrough error in the pixel, and the maximum allowable leakage current for the TFT is also presented. 相似文献
16.
In this paper, four different driver circuits for an active matrix organic light-emitting diode (AMOLED) pixel based on thin film transistor (TFT) technology are analyzed and compared. In particular, the comparison analyzed accuracy, driving speed, power consumption and area occupied. Moreover, in order to allow array simulations, the RC equivalent models of the pixel were also derived. The results were achieved considering a QVGA display (320×240), a line frequency of 60 Hz, and were verified by simulations with AIM-SPICE. 相似文献
17.
Seon Pyo Hong Dong Sung Moon Byung Seong Bae 《Analog Integrated Circuits and Signal Processing》2012,70(1):157-162
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. 相似文献
18.
Driving schemes for a-Si and LTPS AMOLED displays 总被引:5,自引:0,他引:5
Design of stable active matrix organic light-emitting diode (AMOLED) displays comes with significant challenges that stem from the electrical property of the backplane materials, line parasitics in the matrix, and the opto-electronic property of the organic light-emitting diode (OLED). This paper reviews voltage and current programming schemes for AMOLEDs. Following a systematic review of pixel circuits, design considerations are examined for both current and voltage schemes with focus on stability and programming speed for both amorphous silicon (a-Si) and low temperature polysilicon (LTPS) pixel circuits. In particular, spatial parameter variations and stability, which hinder reliable operation of AMOLED display backplanes, are discussed. Analysis shows that while driving schemes reported hitherto maybe suitable for small and medium size displays, new schemes are critically needed for large-area high-resolution AMOLED displays. 相似文献
19.
KeeChan Park Jae-Hong Jeon YoungIl Kim Jae Beom Choi Young-Jin Chang ZhiFeng Zhan ChiWoo Kim 《Solid-state electronics》2008,52(11):1691-1693
An active-matrix organic light-emitting diode (AMOLED) display based on the polycrystalline silicon backplane technology has been fabricated that employs a new pixel circuit to compensate for the variation in the threshold voltage of the thin film transistors (TFT). The new pixel circuit also copes with the voltage drop in the supply line and a very high contrast ratio can be achieved. The uniformity of the new AMOLED display is remarkably improved compared with the basic two-TFT pixel structure, and it can be readily applied in the mass production of commercial AMOLED displays. 相似文献
20.
Two improved four thin-film-transistors (TFTs) pixel electrode circuits based on hydrogenated amorphous silicon (a-Si:H) technology have been designed. Both circuits can provide a constant output current level and can be automatically adjusted for TFT threshold voltage variations. The circuit simulation results indicate that an excellent linearity between the output current and input current can be established. An output current level higher than ~5 μA can be achieved with these circuits. This current level can provide a pixel electrode brightness higher than 1000 cd/m2 with the organic light-emitting device (OLED) having an external quantum efficiency of 1%. These pixel electrode circuits can potentially be used for the active-matrix organic light-emitting displays (AM-OLEDs) 相似文献