[paper] Model for TFT Used in a CMOS Inverter Amplifier

Adelmo Ortiz-Conde^a, CarlosÁvila-Avendaño^b, Jesús A.Caraveo-Frescas^b, Manuel A.Quevedo-López^b and Francisco J.García-Sánchez^a

A polylogarithmic model for thin-film transistors used in a CMOS inverter amplifier

Solid-State Electronics

Volume 188, February 2022, 108218

DOI: 10.1016/j.sse.2021.108218

   
a Solid State Electronics Laboratory, Universidad Simón Bolívar, Caracas 1080, Venezuela
b Materials Science and Engineering Department, University of Texas at Dallas, Richardson, TX 75080, USA

Abstract: This article presents a generalization of a transregional polylogarithmic model, previously proposed for continuously describing the transfer characteristics of polycrystalline and amorphous Thin Film Transistors (TFTs) at all levels of inversion. The present generalization entails including the necessary drain voltage dependencies to be able to describe also the output characteristics. The model is tested by using it in the design and analysis of a CMOS inverter amplifier consisting of poly-Si n- and p-channel TFTs fabricated at low temperature and pressure. The transistors are biased below threshold so that the CMOS amplifier circuit operates in weak conduction, having in mind energy saving considerations. The validity of the proposed model has been ascertained by comparing model simulations to actual measured data from individual poly-Si TFTs and from the CMOS amplifier circuit. The simulations of the CMOS inverter amplifier are compared to the results obtained using look-up table-type simulations.

Fig: Normalized current with respect to its maximum value versus gate bias for two different values of drain bias (top). The curve for the higher drain bias (blue dash line) is shifted to the right of that for the lower drain bias (red continuous line), indicating that VT increases as VDS increases. The corresponding Y function versus gate bias (bottom) illustrates a similar increase of VT with VDS. 

Acknowledgment: The authors would like to thank the reviewers and the editor for their valuable work, which has led to a significant improvement in the quality of this article.