Question

Why is a fast-look-ahead carry circuit used in the 7483 4-bit full-adder?

(a) To decrease the cost

(b) To make it smaller

(c) To slow down the circuit

(d) To speed up the circuit

I got this question in an interview for internship.

My enquiry is from 4-Bit Parallel Adder/Subtractor topic in section Arithmetic Circuits of Digital Circuits

Answer 1

Right choice is (d) To speed up the circuit

For explanation: A Carry Look Ahead (CLA) Adder is a type of adder that reduce the propagation delay. A fast Carry Look Ahead Adder is more fast than a normal CLA. Since, it is easy to implement and can be implemented on any types of chip and have the capability to reduce propagation delay, which helps in increasing the speed of 7483 4-bit full-adder.