An a-IGZO TFT pixel circuit with improved current mirror for active matrix organic light emitting diode displays

Abstract

Active matrix organic light emitting diode (AMOLED) displays based on amorphous indium-gallium-zinc oxide thin-film transistor (a-IGZO TFT) pixel circuit encounter problems as instability of threshold voltage (VT) under gate voltage bias-stress, the non-uniformity of mobility (μ) resulting from the large area TFT scale fabrication, and OLED degradation, etc. In this paper, we proposed a current compensation method. An improved current mirror is designed to overcome the channel length modulation effect of TFTs. The SPICE simulation results show that the proposed scheme not only effectively compensates for non-uniformity related with deviations of VT and μ in a-IGZO TFTs, the OLED degradation, but also guarantees a good linearity between IDATA and IOLED.