Josephson modified variable threshold logic gates for use in ultra-high-speed LSI

Abstract

A gate family called modified variable threshold logic (MVTL) is proposed. The OR gate is a two-junction interferometer with one magnetically coupled control line. Magnetic coupling and current injection are used to switch the logic state of the gate. By optimizing the gate parameters, an operating margin of +or-43% and a switching speed of 2.5 ps/gate are obtained. the gate area is 30 mu m*24 mu m with a 1.5- mu m minimum junction diameter. The gate family consists of an OR gate, a single-junction AND gate, and a timed inverter (TI) that consists of the OR gate, a junction, and resistors. The delay time of the gate operated in the actual circuit was found to be less than 10 ps. Circuits having up to 1000 gates, the critical path model of a 16-bit*16-bit multiplier, and a 16-bit arithmetic logic unit have been successfully operated. When the Josephson gate is operated with three-phase power, it is possible to construct any sequential circuit without the complex latch circuit required to prevent the race condition for one- or two-phase power supplies.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>