SNS programmable voltage standard

Superconductor-Normal-Superconductor (SNS) junctions have been used in the design and fabrication of a 1-V rapidly programmable voltage standard. The superconducting circuit is a series array of 32 768 Nb-PdAu-Nb junctions with taps that divide the array into a binary sequence of smaller array segments with a minimum segment size of 128 junctions. The 16-GHz drive frequency is set by the characteristic frequency of the junctions. A computer-controlled 8-channel bias system controls the current in each segment and allows the rapid selection of any one of 513 discrete voltage levels. The system is designed for fast dc measurements and the synthesis of precise ac waveforms.