Simulation Analysis and Energy-Saving Techniques for ERSFQ Circuits

Energy-efficient rapid single flux quantum (ERSFQ) circuits have become a viable alternative for the implementation of superconducting circuits due to a large amount of static power consumption in RSFQ circuits. ERSFQ circuits are built upon the popular RSFQ logic circuits by replacing the power-dissipating resistor bias network with a bias network consisting of active devices. In this paper, a simulation study of ERSFQ biasing scheme is carried out by building simulation test benches for both synchronous and asynchronous ERSFQ circuits. A study is carried out to present the optimum value of biasing inductance, influence of the feeding Josephson transmission line (FJTL) and the effect of its size, the effect of the feeding clock frequency, and the effect of the circuit operating frequency. An innovative clock-choking mechanism using magnetic Josephson junctions is also proposed for the FJTL in the case of no logic circuit activity for a current-recycling circuit block, which would help in eliminating the dynamic power consumed due to the switching of bias junctions in a logic circuit. Simulation results for current recycling ERSFQ circuits are presented along with a strategy for implementing large superconducting circuits.