Magnetically coupled Josephson D/A converter
Precise, accurate D/A conversion becomes increasingly difficult at high frequencies, especially for low-power devices. The authors have developed a superconducting D/A converter based on the Josephson effect. Following a design of Hamilton et al. (1995), they have added magnetic coupling of the digital input lines to simplify the input interface. In addition, they have converted to a balanced two superconducting quantum interference device (SQUID) unit cell, which allows input-to-output isolation and isolation between input lines white doubling output voltages. Their initial demonstration consists of a 2-bit NbN D/A pumped at 12 GHz, producing output levels of 0, 50, 100, and 150 microvolts into a 50-ohm load with low-speed digital input.