10-40GHz design in SiGe-BiCMOS and Si-CMOS –udlinking technology and circuits to maximizeudperformance

摘要

This paper reviews the relevance of theudwidely used device metrics fT, fmax as well as the recentlyudintroduced device metrics fA and fcross for broadband circuituddesign. Usually, IC processes are benchmarked on the basisudof their fT and fmax. For most circuit applications however,udthere is only an indirect relation between fT, fmax and circuitudbandwidths. Since the differential pair amplifier is a keyudbuilding block in broadband circuits, the metric fA providesuda nearly direct relation to broadband circuit performance.udThis is demonstrated via the maximum operating frequencyudof a current-mode logic frequency divider, processed in 3udgenerations of a BiCMOS process. Metric fcross is valuableudfor the design of circuits employing a cross-coupleduddifferential pair as active negative resistance, such as in LCVCOs.udThe metrics can be expressed in terms of transistorudparameters (e.g., Rb, Cbc, …), allowing to derive a linkudbetween circuit performance and technology. Based on ourudexperience, we evaluate IC processes on the basis of fT, fAudand fcross rather than fT and fmax.