An equivalent 4T1C pixel circuit compensating threshold voltage variation and mobility variation

A design for voltage-programming pixel circuit using amorphous InGaSi Zinc Oxide Thin-Film Transistors to improve the performance of AMOLED displays was presented in this paper. The circuit includes a TFT driver, 5 TFTs, and 2 capacitors. The circuit is built on the two neighboring pixels. A drive TFT and a switching TFT are shared by two neighboring pixels. Thus, an equivalent four transistors and one capacitor (4T1C) pixel circuit is obtained for one pixel. In this circuit, at the threshold voltage extraction stage, the threshold voltage of the transistor is determined. At the data input stage, the discharge voltage associated with the mobility is produced. The electrical circuit is designed to compensate for changes in both threshold voltage and mobility, thereby preventing image flicker. Simulation results indicate that when there is a threshold voltage variation of ±0.5 V, the OLED current error rate is kept below 4.7%, and below 4.1% when the mobility changes by ±30%.