Two novel cross-cascode differential amplifiers
Yu. M. Bruck, Michael Zelikson · 2005
Two novel cascode circuits, the differential cross-cascode and differential cross-follower, are proposed and investigated. Their fundamental distinction from the differential ordinary cascode consists of the input signal voltage being applied simultaneously to the inputs of common emitter/source and common base/gate stages, and in addition the inputs of CE/CS and CB/CG are cross-coupled. We show that the input signal is amplified in the input circuit, and 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 actual 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).