Jun 21, 2011 posted by Achal 0
Cascode (shown in Fig. 1) is well known and widely used circuit for creating large-impedances in integrated circuits. Cascode circuits also provide another advantage i.e. isolation between input and output ports and thereby reducing the Miller-effect and as a result cascodes have a good frequency performance. And when impedances achieved from cascode circuits are not good enough, we go on to use active-cascodes or regulated-cascodes. Even though cascodes are affected by the limitations of headroom (voltage swing), there are work-arounds for this problem that have been figured out by circuit designers (the smart engineers again). The question that I want to discuss here is – how did someone (must be a genius) think of this circuit which provides an elegant area-efficient solution for achieving large impedances consequently large voltage gains?