An optimal design of full adder based on 5-input majority gate in coplanar quantum-dot cellular automata

Abstract

Quantum-dot cellular automata (QCA) is one of the alternative technologies that enable nanoscale circuit design with high performance and low power consumption features. In this aspect, QCA wire crossing is a challenging task in the coplanar QCA fabrication, as defects appear to be inherent due to two cell types in single layout structure. This work showcases an extensive structural and power analysis of previous 5-input majority gates. It has been found that the existing 5-input majority gates are not power efficient and the structures are not well optimized. To overcome this, we have proposed a new low-complexity coplanar 5-input majority gate, which consumes less power compared to prior designs. To evaluate the usefulness of proposed gate a new one bit full adder circuit is presented. The proposed full adder is more robust and enjoys single layer wire crossing, via clock phasing, which requires only one type of cell. The results show that the proposed full adder performs equally well compared to existing multilayer designs and performs better in case of previous coplanar full adder designs in all aspects. Our design achieves 20% improvement in cell count and consumes 7% less area in comparison to the best single layer design. QCADesigner tool is used to validate the layout of the proposed designs and QCAPro power estimator tool is used to evaluate the power dissipation of all considered designs.