Active matrix touch sensor detecting time-constant change implemented by dual-gate IGZO TFTs

Abstract

The dual-gate IGZO TFT is proposed to be used in an active matrix touch sensing circuit. The circuit contains only one TFT with a RC low-pass filter, since the dual-gate IGZO TFT can be controlled by both its top and bottom gates. The simplest structure maximizes the sensing pad area in the pixel. A touch event on the sensing pad forms a capacitance and thus increases the RC time-constant of the scan pulse fed to the gate of TFT. Thus, a significant transient ON current is generated to be the sensing signal. The current is so large that it can be easily read out and thus the power and cost of peripheral ICs can be reduced. In this paper, the robustness of the circuit to environment in operations is discussed. (c) 2012 Elsevier Ltd. All rights reserved.