Josephson analog-to-digital converter using self-gating-AND circuits as comparators

This paper describes the comparator stage of a Josephson junction 4-bit A/D converter. It utilizes the periodic nature of SQUID's to make a 4-bit A/DC with only four comparators for parallel conversion. A new design for a symmetrical three-junction SQUID provides identical lobes beyond the four required. The necessary short aperture time is obtained by imbedding the SQUID's in self-gating-AND circuits that detect the input signal only during the rising edge of the clock. A binary resistor divider provides the correct proportions of the input signal to the four comparators. Both computer simulation results and low-frequency test results are presented.