| In the last decade, CMOS technology has experienced rapid advancement as the minimum feature size has been steadily scaled down to a sub-micro region, so that today the channel length for MOS FET devices range from 0.8 um to 0.13 um. Unity current gain frequency ƒT of an NMOS FET has increased from 10 GHz to 90 GHz. When the channel length of an NMOS FET is 0.5 um or shorter, both transconductance and unity current gain frequency is comparable to and can even surpass that of a traditional GaAs MESFET radio frequency (RF) active device. This has opened new application areas for traditional digital CMOS technology. Today, CMOS is one of the technology choices for radio frequency integrated circuits (RFIC), featured by its low cost and more circuit functionalities in a single chip. However, the CMOS process faces some challenges in RF applications. In particular, one of those challenges is the low Q of RF passive components due to the substrate loss caused by conductive silicon.;In this work, 0.5 um CMOS active devices have been characterized in comparison with their GaAs counter part - MESFETs. The RF inductor on a SiO2-silicon substrate has been explored in a systematic way using different resistivity silicon wafers. The microstrip line on a SiO2-silicon substrate and other CMOS passive components, such as capacitors and resistors, have also been studied. Finally a 0.5 um CMOS fiber-optic preamplifier has been designed and measured to evaluate the RF integrated circuit performance in CMOS. Very low noise performance was achieved compared to other published results that used a similar gate length CMOS process, and a new two-stage transimpedance amplifier topology was adopted for an optical system preamplifier design. A transimpedance amplifier's performance, with the same circuit topology, has also been explored, by circuit simulation, in a 0.35 um channel length CMOS process. |
