A custom integrated circuit comparator for high-performance sampling applications

The authors report on the design and performance of an application-specific integrated circuit (ASIC) comparator that has been optimized for equivalent-time waveform sampling applications. The comparator, which has been fabricated with an 8.5 GHz f_T , bipolar silicon process, features a bandwidth of >2 GHz, a settling-time accuracy of 0.1% in 2 ns, and almost total elimination of `thermal tails´ in the settling response. Several novel design features that have been used to achieve this level of performance are presented. The comparator can be used in a sampling system for both frequency-domain measurements, e.g. wideband RMS voltage measurements, and high-accuracy time-domain pulse measurements