A COMPARISON OF 2 TYPES OF SINGLE FLUX QUANTUM COMPARATORS FOR A FLASH ADC WITH 10 GHZ INPUT BANDWIDTH

We compare the SQUID wheel/quantum Flux Parametron (QFP) comparator to a new Rapid Single Flux Quantum (RSFQ) compatible design. Both have b een simulated to demonstrate similar to 0.5 ps threshold accuracy whic h would permit the construction of a flash analog-to-digital converter with six effective bits of resolution at 10 GHz input bandwidth, over three times better than the best performance demonstrated with any te chnology. At lower input frequencies, both designs have demonstrated t hat a 10-bit flash ADC is possible. Although simulations of the QFP-ba sed design are more accurate at high signal slew rates due to its symm etry, the RSFQ-based design has a better signal-to-noise ratio and a f aster and more flexible clocking scheme which ultimately prove to be m ore important.