An efficient design for reversible Wallace unsigned multiplier

Abstract

Today, reversible logic can be used for designing low-power CMOS circuits, optical data processing, DNA computations, biological researches, quantum circuits and nanotechnology. Sometimes using of reversible logic is inevitable such as build quantum computers. Reversible logic circuits structure is much more complicated than irreversible logic circuits. Multiplication operation is considered as one of the most important operations in the ALU unit. In this paper, we have proposed two 4 × 4 reversible unsigned multiplier circuits in which Wallace tree method is used to reduce the depth of circuits. In first design, the partial products circuit is designed using TG and FG gates so that TG is used to produce the partial products and FG for fan-out. In the second design, TG and PG gates are used to produce the partial products and no fan-out is required. Moreover, we have used PG gate and Feynman' block as reversible half-adder (HA) and full-adder (FA) in the summation network, respectively. In the first design, the main purpose is to decrease the depth of the circuit and increase the circuit speed. In the second design we would attempt to improve quantum parameters the number of garbage outputs, constant inputs and quantum cost. The evaluation results show that the first design, in terms of delay, is the fastest circuit. Also, the second design in terms of the number of constant inputs, garbage outputs and quantum cost is better than other designs.