Power supply regulators for Josephson logic

Josephson logic circuits require a high frequency (f up to 1 GHz) trapezoidal, regulated power supply waveform with an amplitude on the order of 6-12mV (1). This can be formed from an incoming sinusoidal waveform at f/2 by using two or four Josephson tunnel junctions in series as the regulating device. Alternating current is supplied to a number of such regulators located at electrically equivalent positions on a logic chip by a transformer distribution system (2). The regulator with its highly nonlinear current-voltage characteristic clips the incoming ac to produce a trapezoidal current waveform that is supplied to the logic gates [Figs. 1 (a) and 1(b)]. Logic functions are performed when the voltage across the regulator is in the positive and negative regulated regions; the latching logic devices reset as the polarity reverses. The three key concerns in the design of the regulator are duty cycle, skew, and voltage regulation.