A custom integrated circuit comparator for high-performance sampling applications

The design and performance of an application specific integrated circuit (ASIC) comparator that has been optimized for equivalent-time waveform sampling applications is reported. 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. The design has eliminated thermal effects, common in other comparators, than can cause errors and affect the voltage settling time. 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