Performance of CMOS and Floating-Gate Full-Adders Circuits at Subthreshold Power Supply

To reduce power consumption in electronic designs, new techniques for circuit design must always be considered. Floating-gate MOS (FGMOS) is one of those techniques and has previously shown potentially better performance than standard static CMOS circuits for ultra-low power designs. One reason for this is because FGMOS only requires a few transistors per gate and still retain a large fan-in. Another reason is that CMOS circuits becomes very slow in subthreshold region and are not suitable in many applications while FGMOS can have a shift in threshold voltage to increase speed performance. This paper investigates how the performance of an FGMOS fulladder circuit will compare with two common CMOS full-adder designs. Simulations in a 120 nm process shows that FGMOS can have up to 9 times better EDP performance at 250 mV. The simulations also show that the FGMOS full-adder is 32 times faster and have two orders of magnitude higher power consumption than that for CMOS.