Quaternary full adder cells based on carbon nanotube FETs

Abstract

This study presents two quaternary full adder cells using multithreshold carbon nanotube field effect transistors (CNTFETs). The first proposed design is based on quaternary multiplexers and has a regular structure. The second proposed approach is based on new efficient quaternary-to-binary and binary-to-quaternary radix converters, which considerably reduces the design complexity and leads to higher energy efficiency. In the proposed designs chirality of the CNTFETs is utilized for threshold voltage control. Extensive simulation results using HSPICE and the Stanford CNTFET model at 32 nm feature size are reported to demonstrate that the proposed quaternary full adders perform correctly under severe process voltage and temperature variations. The results also show that the proposed design using radix converters achieves up to 80 % lower PDP as compared with its CNTFET-based quaternary multiplexer-based counterpart.