Operating margins for a pulse-driven programmable voltage standard

We have designed and fabricated a Josephson voltage standard where the voltage can be rapidly and continuously programmed by changing the repetition frequency of a pulse drive. Simulations are made to optimize the operating margins of the circuit for different pulse waveforms. The response of a 1000-junction array of Nb-PdAu-Nb junctions is measured, and constant-voltage step heights are characterized as a function of the pulse amplitude, pulse width, and frequency. A dc bias range of 0.62 mA is demonstrated over a continuous voltage-tunable range from -6.2 mV to +6.5 mV.