HP Labs Technical Reports



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Dynamic Characterization of a-Si TFT-LCD Pixels

Aoki, Hitoshi

HPL-96-19

Keyword(s): amorphous, Si, TFT, modeling, AMLCD, pixel simulation


Abstract: A dynamic analysis of an amorphous silicon (a-Si) Thin-Film-Transistor-Liquid-Crystal-Display (TFT-LCD) pixel is presented using new a-Si TFT model and new Liquid Crystal (LC) capacitance models for SPICE simulators. This analysis is useful to all Active Matrix LCD designers for evaluating and predicting the performance of LCD's. The a-Si TFT model is developed to simulate important a-Si TFT characteristics such as off-leakage current, threshold voltage shift due to voltage stress and temperature, localized states behavior, and bias- and frequency-dependent gate-to-source and gate-to-drain capacitance. In addition, the LC Capacitance model is developed using simplified empirical equations. The modeling procedure is useful to TFT and LCD designers who need to develop their own models. Since our experiments simulate critical TFT-LCD transient effects, such as the voltage drop due to gate-to-source capacitance and dynamic off-leakage current, it is possible to accurately characterize TFT-LCD's in the time domain. The analysis and models are applicable to today's optical characterizations of Flat-Panel-Displays (FPD's).

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