Pipelined Carry Lookahead Adder Design in Quantum-dot Cellular Automata

Quantum-dot cellular automata (QCA) is a novel nanotechnology for electronic circuits. The QCA cell is a funda- mental building block. QCA circuits are different from transistor circuits mainly because the basic computational gate is a majority gate and interconnections consume time and area. It's easy to design a pipelined circuit and coplanar wire crossings for a two dimensional structure, but complex designs consume more time due to the wire. The estimation of timing is difficult until the layout is finished. This paper proposes a pipelined carry lookahead adder design in QCA. Using the QCADesigner, 4, 16, and 64 bit carry lookahead adders are designed and simulated. Those designs are compared with ripple carry adders according to the complexity, area, and timing. The final layouts show modular designs and small delays for the carry lookahead adder.