Three Input Logic Synthesis And Circuit Design In Qca

Integrated circuit technology has been developing rapidly followed Moore's Law since the advent of complementary metal oxide semiconductor(CMOS).The feature size of devices is getting smaller with the advancement of technology.The physical basis of the circuits changes when the size decreases to a certain degree.Issues such as extremely high density,high power consumption,complex arrangement of wires and interference of circuits begin to occur.Hence,a novel device which can replace traditional CMOS devices is demanded.As an emerging nano-device,Quantum-dot Cellular Automata(QCA)becomes a hot topic for low energy dissipation,small area and high frequency.Traditional circuits can be implemented from And or Or gate to adders,multipliers,memories and so on.Thus,QCA has a bright prospect.For traditional circuits,Boolean function expressions generally divided into SOP or POS are the most efficient way to describe circuits.Since QCA circuits have a unique device,namely the majority gate,a new type of logic expression is needed to describe the circuit functions.The paper is devoted to studying how to convert traditional logic functions from Boolean expressions to the majority gate logical expressions.Two classical conversion methods are introduced in this paper.One is the standard function method based on cube,which can be classified as three inputs and four inputs.The three-input standard function is optimized using proposed methods.And verification and realization are made in the four-input standard function.The other method is logic synthesis based on functions,which also can be classified as three inputs and four inputs.The three-input logic synthesis includes the method that searching for f1,f2 and f3,Boolean nonadjacent method and three-input nodes network synthesis method based on exhaustive search.Four-input conversion method is fourinput function table checking method.Each method illustrates the conversion process with an example.The motorized conversion from all the three-input Boolean function expressions to the majority logical expressions is achieved.The proposed three-input majority logical expressions is optimized in terms of majority gates,inverters and logic layer compared with existing three-input logic synthesis methods.The correctness is verified by full adders and frequently-used three-input circuits.The cases are simulated by QCADesigner,which demonstrates that functionality of all the cases is correct.