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/sub 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.>