Nb/Al/sub 2/O/sub 3//Nb-Josephson voltage standards at 1 volt and 10 volt

Series array Josephson voltage standards in Nb/Al/sub 2/O/sub 3//Nb technology producing stable reference voltages up to 12 V with step amplitudes of about 70 mu A are reported. The 1-V standard chips contain 2000 tunnel junctions, and the 10-V standard chips 20,000 junctions. The 10-v design has been optimized to reduce the total circuit area to 10 mm*27 mm and the total active tunnel junction area to only 7 mm*13 mm The incident microwave power at 70 GHz is distributed over 64 parallel stripline paths. At 10 V, the voltage steps are usually stable for 30 min. The best result achieved was 80 min. This, allows the long-term output voltage recording of a series connection of Weston cells, the direct calibration of 10-V Zener reference standards, linearity measurements of digital voltmeters, and the determination of the noise spectra of Zener references and Weston cells.<>