Frequency Limitation Due to Switching Transition of the Bias Current in Bidirectional RSFQ Logic

Abstract

Switching time limitations of the ac bias current of Josephson junctions in bidirectional rapid single flux quantum (RSFQ) logic circuits are investigated in order to determine the limits to the maximum possible operating frequency. We introduce a new approach based on modifying the bias current parameters and determining the inductance values in the circuit for reducing the switching transition time of the bias current through the junctions. We have simulated and optimized the timing and the operation of the bidirectional nondestructive readout and Josephson transmission line cells in this respect to demonstrate the results of utilizing the proposed approach. We successfully reduced the unwanted spike-type signals across the inductances which are made through the transitions during the fast switching times limiting the operation frequency. This is while we have also removed the consequent destructive spikes at the output. We have included the effects of other determining parameters of the circuit in this investigation and found their relatively optimal values to improve the temporal behavior of the bidirectional RSFQ cells. The results of the proposed approach leading to the fastest possible operation of the considered gates obtained in this work are thoroughly reported.