Voltage Driving Scheme Using Three TFTs and One Capacitor for Active-Matrix Organic Light-Emitting Diode Pixel Circuits

This work presents a new active-matrix organic light-emitting diode (AMOLED) pixel circuit with a novel driving scheme that is based on low-temperature polycrystalline-silicon thin film transistors (LTPS TFTs). The proposed circuit that consists of one driving TFT and two switching TFTs, which are all p-type, can successfully compensate for not only variations in the TFT threshold voltage but also the current-resistance (IR) voltage drop in the power line. The functionality of the pixel circuit for the array structure and the uniformity of organic light-emitting diode (OLED) current are verified using H-Simulation Program with Integrated Circuit Emphasis (HSPICE). According to the results of a simulation, over the entire range of tested data voltages (-4.5 to -2.5 V), the relative errors of the OLED current of the proposed circuit are below 1.2% when the driving TFT threshold voltage varies from -0.5 to +0.5 V.