Abstract

In this paper we present two topologies for differential high-sensitivity comparators, suitable to be implemented in GaAs MESFET/HEMT technologies. Both topologies use positive feedback to compensate for the moderate specific transconductance of GaAs devices, and differ for the implementation of the summation node. The linear and non-linear behaviour of the circuits are analysed, in order to define limitations due to process parametric dispersion using state of art technologies. Circuit simulations are reported to estimate slew rate performance. The topology based on the cascade of two differential cells shows better slew rate performance and results not very sensitive to process parameter dispersion, whereas the topology based on the shunt connection of two differential pairs is more sensitive to process variations but allows to electronically control its DC transfer function.