Question

Which of the following logic families has the shortest propagation delay?

(a) S-TTL

(b) AS-TTL

(c) HS-TTL

(d) HCMOS

This question was posed to me in an internship interview.

Question is taken from Digital Integrated Circuits in chapter Boolean Algebra and Minimization Techniques and Logic Gates of Digital Circuits

Answer 1

Right option is (b) AS-TTL

For explanation: AS-TTL (Advanced Schottky) has a maximum clock frequency that is 105 MHz. So, the propagation delay will be given by 1/105 sec which is the lowest one. It is followed by S-TTL and HCMOS in terms of increasing propagation delay.