RSFQ-based D/A converter for AC voltage standard

Digital to analog converters based on the Josephson effect are promising fo r voltage standards, because they produce voltage steps with ultimate preci sion and stability. In this paper, we describe a project to develop a Josep hson D/A converter designed for synthesizing a sinusoidal waveform with met rological accuracy. The D/A converter is based on RSFQ (Rapid Single Flux Q uantum) logic circuits, and consists of a frequency multiplier (FM), a puls e distributor (PD), and a number of voltage multipliers (VMs). Each VM circ uit, corresponding to the n-th bit digital code, multiplies the number of S FQ pulses by a factor of 2(n). By gating the input SFQ pulses from the FM t o the VMs using the PD circuits, a programmable output voltage is obtained. Possible sources of uncertainties in the measurement of the rms value of t he synthesized sine wave are discussed.