EXPERIMENTAL IMPLEMENTATION OF THE 8 BIT ANALOG-TO-DIGITAL CONVERTER

Two bit Single Flux Quantum (SFQ) Analog to Digital Converter (ADC) has been recently realized and successfully tested. The new design and the improved fabrication technique of superconducting microcircuits has allowed us to expand the number of bits up to eight. This converter consists of a comparator and reversible ripple counter. The comparator is loaded with two SFQ transmission lines which independence from the input signal. Non-destructive read-out of the counter contents is carried out by SFQ/DC converters which is connected to the each counter bit. The integrated circuit is fabricated using 4 mu Nb-AlOx-Nb trilayer technology with critical current density about 1000 A/cm2. Careful investigation of the ADC input circuits have been performed.