8-bit Brent-Kung Adder

The Brent-Kung adder is a parallel prefix adder that requires 2(log2N)-1 stages.It was originally proposed as a simple and regular design of a parallel adder that addresses the problems of connecting gates in a way to minimize chip area. Accordingly, it is considered one of the better tree adders for minimizing wiring tracks, fanout, and gate count and is used as a basis for  any other networks. The operation of parallel prefix adders depends on the notion of group carry propagate and generate signals.In essence, a group of bits generate a carry when its carry is true independent of the carry-in and propagate a carry when its carryout is true when there is carry-in.