Flux-to-Voltage transfer function of the series-SQUID array with grain-boundary Josephson junctions

The factors affecting the flux-to-voltage transfer function of the series-SQUID array with grain-boundary Josephson junctions were investigated. By using the proposed critical-current-modulation model, it is found that the voltage swing of the series-SQUID array is suppressed greatly by the spread in critical currents of Josephson junctions. For the inductance L = 80 pH and the logarithmic average critical current 2I/sub ave/ = 20 /spl mu/A of the component SQUID, the allowed spread in critical currents of Josephson junctions is 0.4I/sub ave/ to 2.2I/sub ave/ for achieving the low flux noise with the series SQUID array.