Magnetically coupled Josephson D/A converter

Precise, accurate DIA conversion becomes increasingly difficult at high fre quencies, especially for low-power de,ices, The authors have developed a su perconducting DIA converter based on the Josephson effect. Following a desi gn of Hamilton ct al. [1], they have added magnetic coupling of the digital input lines to simplify the input interface. In addition, they have conver ted to a balanced two superconducting quantum interference device (SQUID) u nit cell, which allows input-to-output isolation and isolation between inpu t lines while doubling output voltages. Their initial demonstration consist s of a 2-bit NbN D/A pumped at 12 GHz, producing output levels of 0, 50, 10 0, and 150 microvolts into a 50-ohm load with low-speed digital input.