Four different types of Adders are used to construct an 8-bit adder. The characteristic of each full adder in terms of delay is as follows –

Type	Symbol	Carry generation	Sum generation
A	FAA	18 nsec	42  nsec
B	FAB	32 nsec	23  nsec
C	FAC	27 nsec	169 nsec
D	FAD	23 nsec	72  nsec

The structure of the FA is as follows:

The maximum no of addition per second that the above adder can perform is –