Novel inspection-based mid-band derivations for CMOS cascodes and g m-boosted topologies along-with simplified compound structure gain-analysis

Abstract

This article demonstrates simplified mid-band derivations for CMOS cascode and gm-boosted cascode. While the cascode mid-band analysis is addressed in some textbooks through varying brief treatments, it is provided in this paper in a more in-depth and consolidated form using an easy approach. The detailed analysis of gm-boosted cascode stage is mostly not available in textbooks (or any Web source) despite being an important analog building block in achieving gain enhancements. The mid-band analysis of this stage is made easy in this paper using a simple short circuit and inspection technique. There is no need to write or solve lengthy equations. Transformation of dependent current sources through "opportunistic short circuits" is utilized often in achieving this ease in derivation. An interesting new concept of "Algebraic ground" or "Meta-ground" is introduced in relation to the gm-boosted cascode. Some novel compound cascode stages with simplified approach to their mid-band derivations is also provided. Additional insight is also provided through a comparison of the cascode with the gm-boosted cascode using the simplified models and derivations which is rarely available elsewhere.