A Small-Area and Low-Power Scan Driver Using a Coplanar a-IGZO Thin-Film Transistor With a Dual-Gate for Liquid Crystal Displays

This letter proposes a small-area and low-power scan driver using a coplanar amorphous indium-gallium-zinc oxide (a-IGZO) thin-film transistor (TFT) with a dual gate for TFT liquid crystal displays. The size of the pull-up TFT of the proposed scan driver is reduced by 30% when the ON-current of the coplanar a-IGZO TFT with a dual gate increases by 65%, when compared with the coplanar a-IGZO TFT with a single gate at a Vgs of 10 V and a Vds of 10 V. This reduced size of the pull-up TFT decreases the capacitance of the clock signal (CLK) bus line. Owing to the reduced capacitance, the resistance of the CLK line can be increased while maintaining the resistance and capacitance delay of the CLK, and thereby the width of the CLK bus line can be reduced. Moreover, the dual gate, which forms an overlapped capacitor to bootstrap the gate voltage of the pull-up TFT, can further reduce the area of the scan driver. The width and measured power consumption of the fabricated scan driver with the proposed TFT are 2.63 mm and 2.41 W, which are both reduced by 20% compared with those of the scan driver with the conventional TFT.