DESIGN OF LOW POWER HIGH SPEED CNTFET ADDER SUBTRACTOR

Abstract

Multi-valued logic design itself is not sufficient to achieve the performance improvement in digital system design in nanotechnology. The need to replace silicon devices with some more efficient new devices are required so as to meet the power improvements in the nanoscale region. Among various devices explored, CNTFET is the most promising alternative to replace conventional MOS transistors. These nano devices have the benefits of low power consumption due to reduced leakage component, ballistic transport operation even at low supply voltages makes them suitable for high frequency and low voltage applications. MVL circuitry has soared in popularity because the threshold voltage of the CNFET device is somewhat adjustable by the diameter of carbon nanotubes. CNFET is used for high performance, high stability and low-power circuit designs as an alternative material to silicon in recent years. Carbon Nanotube Filed-Effect Transistor (CNFET) is one of the promising alternatives to the MOS transistors. The geometry- dependent threshold voltage is one of the CNFET characteristics, which is used in the proposed design. In this paper, we present a novel high speed Adder-subtractor cell using CNFETs based on XOR gates and multiplexer. Proposed design uses fourteen transistors, ten for full adder and four to modify the cell for subtraction. Simulation results show significant improvement in terms of delay and area saving with respectively compared to the latest design. Simulations were carried out using HSPICE based on CNFET model with optimized design parameters. All designs are simulated at 32nm CNFET with HSPICE. The simulation results show that on average, speed enhancement and area saving of 48% and 11% can be achieved with optimized parameters design over default values of these parameters. The cumulative benefits of the novel adder-subtractor design based CNFET result in an PDP reduction by a factor of 41%.