Measurement and Simulation Study of RSFQ OR gate

There are several simulation programs in studying superconductor RSFQ (Rapid Single flux Quantum) electronic devices, which include WRspice, WinS, PSCAN, and JSIM. Even though different research groups use different simulation programs, it is not well known about which program gives the simulation results closer to the measurement values. In this work, we used both WRspice and WinS to simulate RSFQ OR gate and to compare the results from the different simulations. This comparison would help in deciding which program is better in the RSFQ circuit design. In the confluence buffer, which is the one of the main components of the DR gate, the measured bias margins were ${\times}23.2%$, while the margins from the simulations were ${\pm}35.56%$ from WRspice and it 53.1% from WinS. However, with the actual fabricated circuit parameters WRspice gave ${\pm}27%$. In WinS the circuit did not operate. We concluded that WRspice is more reliable.