A new threshold‐voltage compensation technique of poly‐Si TFTs for AMOLED display pixel circuits

Abstract

Abstract— A new threshold‐voltage compensation technique for polycrystal line‐silicon thin‐film transistors (poly‐Si TFTs) used in active‐matrix organic light‐emitting‐diode (AMOLED) display pixel circuits is presented. The new technique was applied to a conventional 2‐transistor—1‐capacitor (2T1C) pixel circuit, and a new voltage‐programmed pixel circuit (VPPC) is proposed. Theoretically, the proposed pixel is the fastest pixel with threshold‐voltage compensation reported in the literature because of the new compression technique implemented with a static circuit block, which does not affect the response time of the conventional 2T1C pixel circuit. Furthermore, the new pixel exhibits all the other advantages of the 2T1C pixel, such as the simplicity of the peripheral drivers and improves other characteristics, such as its behavior in the temperature variations. The verification of the proposed pixel is made through simulations with HSpice. In order to obtain realistic simulations, device parameters were extracted from fabricated low‐temperature poly‐Si (LTPS) TFTs.

Analysis of the current conduction in poly-Si thin film transistors

“…Compared with a-Si thin film transistors (TFTs), poly-Si TFTs with the high mobility and driving current are a better choice for flat panel displays. Poly-Si TFTs are widely used as pixel transistors and are suitable for realizing the peripheral circuits in the active-matrix liquid crystal displays (AMLCDs) [2] and activematrix organic light-emitting diode (AMOLED) [3] displays. Moreover, poly-Si TFTs have attracted much attention for their applications in memories [4] and sensors [5].…”

A New Voltage-Programmed Pixel Circuit for Enhancing the Uniformity of AMOLED Displays

“…So, the anode potential of OLED should be considered in the design of AMOLED pixel circuit. Several voltage-programmed pixel circuits have been developed to solve the nonuniformity problem for AMOLED displays [5]- [8]. In [5], Goh et al proposed a new four-TFT and one-capacitor a-Si:H TFT pixel circuit with a voltage source method to compensate for the threshold-voltage shift of a-Si:H TFTs.…”