Superconducting A/D converters based on Josephson binary counters

A/D converters (ADC) based on Josephson binary counters are demonstrated in all-Nb technology. These A/D converters use a single SQUID as the flux quantizer front-end with a minimum quantization level equivalent to 2 mu A of input current. A 10-b unidirectional ADC and a 5-b tracking ADC are reported. Both circuits have been tested at 1 MS/s sampling rate with very low power consumption. They also exhibit good linearity within the full dynamic range tested.