Two novel cross-cascode Differential amplifiers

Abstract

Two novel cascode circuits, the Differential Cross-Cascode and Differential Cross-Follower, is proposed and investigated. Its fundamental distinction from the Differential Ordinary Cascode consists in the input signal voltage being applied simultaneously to the inputs of common emitter/source and common base/gate stages, and besides the inputs of CE/CS and CB/CG being cross-coupled. We show that the input signal is amplified in the input circuit, furthermore the input impedance and the current gain increase considerably and the bandwidth is essentially expanded. Simulation results of such a cascode designed with IBM BJT and FET transistors are presented. The actually obtained bandwidths (BJT-18.7 GHz, FET-7.8 GHz) proved as predicted to be more than twice as wide as compared with the bandwidth of the ordinary cascode (BJT-8.6 GHz, FET-3.4 GHz). ©2004 IEEE.