Question

Which of the following combinations of logic gates can decode binary 1101?

(a) One 4-input AND gate

(b) One 4-input AND gate, one inverter

(c) One 4-input AND gate, one OR gate

(d) One 4-input NAND gate, one inverter

This question was posed to me in an interview.

My doubt is from Combinational Circuits topic in section Combinational Circuits of Digital Circuits

Answer 1

The correct choice is (b) One 4-input AND gate, one inverter

For explanation: For decoding any number output must be high for that code and this is possible in One 4-input NAND gate, one inverter option only. A decoder is a combinational circuit that converts binary data to n-coded data upto 2^n outputs.