Adder delay

Ripple-carry adder is logically correct, but may be slow.

Each circuit requires a finite amount of time to give stable outputs when inputs change.

Circuits are working in parallel, but it takes a finite amount of time before the

carry-in from one circuit is available for the next one to use.

Assume time T for each FA to generate output.

n-bit ripple carry adder has O(n) delay: nT

Speed can be improved by using "carry-lookahead":

compute carries in parallel