TABLE OF CONTENTS There has been tremendous progress in consumer RF products with the availability of SiGe BiCMOS and CMOS technologies with good passive elements. Therefore, there is an increasing trend to migrate applications from SiGe BiCMOS to a pure CMOS technology, especially in the sub-10 GHz range. Exploring the design space to create acceptable circuits with MOSFETs will need device models and design kits that are accurate over a wide range of frequency and bias conditions. Since HBTs have been used extensively in RF applications, accurate high-frequency models and design tools are already available.
Most high volume consumer wireless applications still operate below 10 GHz in carrier frequency, and therefore high f T can be potentially traded for significant savings in power. A similar argument can also hold for SiGe HBTs, where f T can exceed 350 GHz [170]. As CMOS technology scales into the sub-100 nm nodes, RF performance can approach that of SiGe, for example, a f T = 243 GHz and f max = 208 GHz for n-MOSFET [171].
A comparison of speed and power performance of the state-of-the-art CMOS and SiGe RF transistors has also been reported by Jagannathan et al. [172]. Figure 10.28 shows the Gummel ( V c = V b = 0 V) and subthreshold I V ( V ds = 1 V) of the HBT and n-FET respectively. Current in the FET at high gate bias is limited by velocity saturation and mobility...
