An Optimized Counter Design using T Flip-Flop in Quantum-Dot Cellular Automata Technology

Conventional CMOS technology have lot of limitations and serious challenges threat this technology when scaled to a nano-level. Several alternative technologies have been proposed as solutions to overcome limitations and challenges encountered by CMOS. Quantum dot-cellular automata (QCA) is an emerging nanotechnology for the development of logic circuits such as combinational and sequential circuits.QCA seems to be best alternative to the conventional complementary metal-oxide semiconductor (CMOS) technology.QCA is a new computing paradigm in nanotechnology that can implement digital circuits with outstanding features such as ultralow power consumption, faster switching speed and extremely density structure . In this paper , a novel area efficient and optimized QCA layout design of sequential circuit T flip flop is proposed by which the QCA layout area has reduced by 57% , cell count improved by 56% in comparison with the earlier best designs. The use of proposed T flip flop in designing sequential circuits like synchronous 2 bit up counter,3 bit up counter and 4 bit up counter has reduced the QCA layout area by 65%,64% and 68% respectively where as QCA cell count are reduced by 53%, 62% and 59%.. The sequential circuits flip flop and counters are designed using three input XOR gate and are implemented by QCA layout. The paper also present the use of proposed T flip flop designed with 3 input XOR gate in designing not only synchronous binary up counters but also in synchronous binary down counter provides a significant reduction in the hardware and complexity than the existing methods. These circuits are simulated using computer aided design tool QCA Designer 2.0.3, which is a design and simulation tool for quantum dot cellular automata. The aim is to maximize the circuit density and focus on a QCA layout that uses minimal number of cells