In class we learned that a carrylookahead adder is faster th

In class we learned that a carry-lookahead adder is faster than a ripple-carry adder. Could you explain why sometimes a designer might still choose a ripple-carry adder instead of a carry look ahead adder?

Solution

The Delay of Ripple carry adders is high compare to Carry look ahead adder . But creating carry look ahead Logic is more complex when the number of Bits is more than 4 bits compare to Ripple carry  .If the design logic get complex the system .its lead complexity to test the circuits which cause the amlfunction in output.So for larger system comapre to speed complexity is more important. thats why designer choosing ripple carry adder