3T0.5C Compensating pixel circuit with all p-type LTPS-TFTs for AMOLED displays

Abstract

A novel pixel circuit with low-temperature polycrystalline-silicon thin-film transistors (LTPS-TFTs) for driving active-matrix organic light-emitting diode (AMOLED) displays is proposed. The pixel circuit is built on two adjacent pixels with six p-type LTPS-TFTs and a capacitor, and thus the equivalent circuit is 3T0.5C in each layout area, which has a superior aperture ratio. The pixel circuit can compensate for the threshold voltage (VTH) deviation of the driving TFT and provide a reverse bias on the OLED to ameliorate the OLED’s lifetime. The simulation results show that the pixel circuit can provide a stable driving current to AMOLED displays and the average error rate of the driving current was 1.8% when the driving TFT threshold voltage deviated by ±0.33 V. Therefore, the proposed pixel circuit with a superior aperture ratio can show high immunity to the driving TFT threshold voltage deviation and significantly improve the uniformity of brightness of AMOLED displays.