Depletion-Mode a-IGZO TFT Scan Driver With a Single Negative Power Source for Low-Power AMOLED Displays

초록

In this paper, we proposed an ultra low-power scan driver circuit based on amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs) for active-matrix organic light-emitting diode (AMOLED) displays. To achieve low-power consumption without additional control signals or power sources, the proposed scan driver employed a single negative power source and a series-connected two-transistor (STT) structure, enabling stable operation even in depletion mode under a Delta V-TH of -1.2 V. Furthermore, extra clock signals with a frequency equal to the frame rate were applied to the pull-down unit to suppress circuit malfunctions caused by threshold voltage shifts in a-IGZO TFTs. The fabricated single-stage scan driver was designed with an area of 402 mu m & times;40 mu m, and experimentally confirmed stable sequential shifting operation across a wide range of clock frequencies from 64.8 kHz up to 194.4 kHz. The simulated power consumption of the proposed scan driver with 2160 stages was calculated as 19.5 mW at the frame rate of 120 Hz.

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