Design and fabrication of a HTC quasi-one junction SQUID based comparator for a 4-bit superconductive flash A/D converter

The design of a quasi-one-junction superconducting quantum interference device (SQUID)-based comparator for an all HTC superconductive 4-b flash analog-to-digital (A/D) converter is proposed and discussed. Ramp-type junctions of YBCO/PBCO/YBCO are used. The inductance can be realized by a stripline between the junctions. Simulations by the PSCAN package show correct behavior of the quasi-one-junction SQUID (QOS) up to frequencies of approximately 1 GHz. The output voltage pulses are periodic with the input current, as expected. In the dynamic simulations, output voltage pulses are observed at an applied flux of around (2m-1) Phi /sub 0//2. Tile junctions in the QOS are structured on two ramp-edges. The operating frequencies will be below 1 MHz in this first design. A first realization uses the YBa/sub 2/Cu/sub 3/O/sub 7-x/ (YBCO) superconductor and PrBa/sub 2/Cu/sub 3/O/sub 7-x /(PBCO) as junction barrier and electrode interlayer material. On a 10-mm*10-mm SrTiO/sub 3/