Threshold-voltage-compensation methods for AMOLED pixel and analog buffer circuits

Abstract

New pixel-circuit designs for active-matrix organic light-emitting diodes (AMOLEDs) and a new analog buffer circuit for the integrated data-driver circuit of active-matrix liquid-crystal displays (AMLCDs) and AMOLEDs, based on low-temperature polycrystalline-silicon thin-film transistors (LTPS-TFTs), were proposed and verified by SPICE simulation and measured results. Threshold-voltage-compensation pixel circuits consisting of LTPS-TFTs, an additional control signal line, and a storage capacitor were used to enhance display-image uniformity. A diode-connected concept is used to calibrate the threshold-voltage variation of the driving TFT in an AMOLED pixel circuit. An active load is added and a calibration operation is applied to study the influences on the analog buffer circuit. The proposed circuits are shown to be capable of minimizing the variation from the device characteristics through the simulation and measured results.