Digital and analog measurements of HTS SFQ RS flip-flops and shift register circuits

We fabricated reset-set(RS) flip-flops and shift registers by using YBCO bi crystal junctions and tested their operations by using a computer-controlle d digital measurement set-up and an analog measurement set-up. The RS flip- flop circuits operated successfully at temperatures up to 71K. The RS flip- flop circuit was observed over 600 computer-generated clock cycles with nea rly no errors. The circuits were reset or set during each clock cycle. By u sing an analog measurement technique, we operated the RS flip-flop circuits at frequencies of up to 500Hz. Since our probe was not designed for high s peed operation, the test speed was limited to this frequency. Although we c ould not operate the shift register completely we observed flux propagation in the shift register.