Novel Current-Scaling Current-Mirror Hydrogenated Amorphous Silicon Thin-Film Transistor Pixel Electrode Circuit with Cascade Capacitor for Active-Matrix Organic Light-Emitting Devices

Abstract

We proposed the hydrogenated amorphous silicon thin-film transistor (a-Si:H TFT) pixel electrode circuit with current-scaling function which is suitable for active-matrix organic light-emitting displays (AM-OLEDs). In contrast to the conventional current-mirror circuit, this circuit with the cascaded storage capacitors can provide a high data-to-organic light-emitting device (OLED) current ratio without increasing the a-Si:H TFT size. Moreover, since the number of signal line is reduced in the proposed pixel electrode circuit, the pixel electrode layout and the driving scheme can be simplified in comparison to previously reported cascade capacitor circuit. Finally, the proposed circuit can compensate for the threshold voltage variation of the driving TFT as well as the device geometric size mismatch and temperature effect.