Performance Analysis of the Josephson dc Flip-Flop

A linear analytical model of the Josephson dc flip-flop is proposed. It describes both the Baechtold's and Hebard's flip-flops. The output signal line is treated as either a single inductance or a transmission line with a finite impedance. The former leads to the lumped model, while the latter leads to the distributed model. The lumped model gives the load condition for successful reset. This is given as a relationship between the CR and L / R time constant, where C is the device capacitance, L is the load inductance, and R is the load resistance. The switching delay is also described as a linear function of the CR and L / R. With the distributed circuit model, the load condition for successful reset is Zo > R. Minimum delay is obtained at Zo = R. Grounding one end of the output signal line reduces the delay more than the nongrounded configuration. The scalar relationship of the switching delay and the power consumption to the design rule is also discussed.