Design of low power and high speed Carry Select Adder using Brent Kung adder

Abstract

In this paper, Carry Select Adder (CSA) architectures are proposed using parallel prefix adders. Instead of using dual Ripple Carry Adders (RCA), parallel prefix adder i.e., Brent Kung (BK) adder is used to design Regular Linear CSA. Adders are the basic building blocks in digital integrated circuit based designs. Ripple Carry Adder (RCA) gives the most compact design but takes longer computation time. The time critical applications use Carry Look-ahead scheme (CLA) to derive fast results but they lead to increase in area. Carry Select Adder is a compromise between RCA and CLA in term of area and delay. Delay of RCA is large therefore we have replaced it with parallel prefix adder which gives fast results. In this paper, structures of 16-Bit Regular Linear Brent Kung CSA, Modified Linear BK CSA, Regular Square Root (SQRT) BK CSA and Modified SQRT BK CSA are designed. Power and delay of all these adder architectures are calculated at different input voltages. The results depict that Modified SQRT BK CSA is better than all the other adder architectures in terms of power but with small speed penalty. The designs have been synthesized at 45nm technology using Tanner EDA tool.