Kerala Engineering Architecture Medical (KEAM) 2008 Entrance Examination Questions on Digital Circuits

As usual, simple questions were asked from the section on digital circuits in KEAM 2008 Examination. Here is the question which appeared in the Engineering Entrance question paper:

The combination of the following gates produces

(a) AND gate

(b) NAND gate

(c) NOR gate

(d) OR gate

(e) NOT gate

The first gate is a NAND gate. The second gate also is a NAND gate. But it functions as a NOT gate since its inputs are shorted. So we have a NAND followed by a NOT and hence the combination functions as an AND gate.

Here is the question which appeared in the Kerala Medical Entrance (2008) question paper:

The output Y when all the three inputs are first high and then low, will respectively be

(a) 1, 0

(b) 1, 1

(c) 0, 0

(d) 0, 1

(e) 1, –1

When all the three inputs are high the NAND gate following the AND gate has both inputs at high level. The output Y of the NAND is therefore low. When all the three inputs are low the NAND gate has both inputs low and hence the output is high. The correct option is (d).

You will find AIEEE 2008 and AIPMT 2008 questions on digital circuits with solution here.