Design of thin-film fully-depleted SOI CMOS analog circuits significantly outperforming bulk implementations

Abstract

Although the reduction of parasitic capacitance and the feasibility of diffusion resistors and capacitors free of junction effects have long been recognized as advantages for the realization of analog circuits on SOI substrates, few SOI analog circuits have been reported mainly because the kink effect severely degrades the output characteristics of thick-film SOI MOSFETs and thereby the performances of analog circuits. Operational amplifier solutions such as the use of body contacts, twin-gate devices or gain-boosting have been proposed but offer little improvement over bulk CMOS counterparts, with the exception of the resistance to elevated temperatures. In the present paper we propose new design models and techniques which, by exploiting the smaller subthreshold swing and body factor of thin-film fully-depleted (FD) SOI MOSFETs, could provide a major breakthrough in order to boost the performances of SOI CMOS analog circuits substantially over bulk implementations, especially in the field of low-voltage low-power applications.