Quantum-dot Cellular Automata (QCA) technology has become a promising and
accessible candidate that can be used for digital circuits implementation at
Nanoscale, but the circuit design in the QCA technology has been limited due
to fabrication high-defect rate. So, this issue is an interesting research
topic in the QCA circuits design. In this study, a novel 3-input Fault
Tolerance (FT) Majority Gate (MG) is developed. Accordingly, an efficient
1-bit QCA full adder is developed using the developed 3-input MG. Then, a
new 4-bit FT QCA Ripple Carry Adder (RCA) is developed based on the proposed
1-bit FT QCA FA. The developed circuits are implemented in the QCA Designer
tool version 2.0.3. The results indicate that the developed QCA circuits
provide advantages compared to other QCA circuits in terms of double and
single cell missing defect, area and delay time.