High performance two-stage bootstrapped GaAs comparator with gain enhancement

A high performance GaAs pHEMT comparator using a double cascode self-bootstrapping configuration with gain enhancement is proposed and investigated in this paper. An improved active load using D-mode HEMT devices is discussed so that the differential-mode input can be further reduced. Fully differential input pair can be realized by either E or D mode FETs. The comparator operates with a single power supply and generates a single output with a buffer stage for driving a large load or subsequent stages. With newly designed comparator, not only small propagation delay of 339 psec, but also high output voltage swing 1.5 V have been demonstrated. Analysis of the adapted comparator circuit and optimization of all transistor sizes for its best performance is also presented in detail. The overall performance is on par with prior attempts.