SFQ-to-level logic conversion by HTS Josephson drivers for output interface

Latching-type driver circuits integrated with high-temperature superconductivity (HTS) junctions and two types of resistor were fabricated. These circuits could successfully perform latching operation by means of a single-flux-quantum (SFQ) signal input. Ramp-edge-type HTS junctions were fabricated by interface engineering and showed a hysteretic current-voltage characteristics under a temperature of 50 K. The critical current (I/sub c/) of these 5-micron-wide junctions was about 0.2 mA and the I/sub c/R/sub n/ product was about 1.7 mV at 4.2 K. The circuits included two types of resistors, which were made of RF-magnetron-sputtered indium-tin-oxide (ITO) and Au films. A driver with a parallel 2-junction-stack could convert an SFQ pulse, which was transformed through several Josephson transmission lines (JTL's) from a DC/SFQ circuit, to a 2.3-mV level signal.