# Logic Gates

 Question 1
In the circuit shown below, X and Y are digital inputs, and Z is a digital output. The equivalent circuit is a A NAND gate B NOR gate C XOR gate D XNOR gate
GATE EE 2019   Digital Electronics
Question 1 Explanation:
The Boolean expression for the output of the digital circuit is shown below The above expression is of XOR gate.
 Question 2
In the logic circuit shown in the figure, Y is given by A Y = ABCD B Y = (A + B)(C + D) C Y = A + B + C + D D Y = AB + CD
GATE EE 2018   Digital Electronics
Question 2 Explanation: Question 3
For a 3-input logic circuit shown below, the output Z can be expressed as A $Q+\bar{R}$ B $P\bar{Q}+R$ C $\bar{Q}+R$ D $P+\bar{Q}+R$
GATE EE 2017-SET-2   Digital Electronics
Question 3 Explanation: $Z=\overline{\overline{P\bar{Q}}\cdot Q\cdot \overline{Q\cdot R} }$
$\;\;=P\bar{Q}+\bar{Q}+Q R$
$\;\;=\bar{Q}(P+1)+QR$
$\;\;=\bar{Q}+QR$
$\;\;=(\bar{Q}+Q)(\bar{Q}+R)$
$\;\;=\bar{Q}+R$
 Question 4
Which of the following logic circuits is a realization of the function F whose Karnaugh map is shown in figure  A A B B C C D D
GATE EE 2014-SET-1   Digital Electronics
Question 4 Explanation: $F=\bar{A}\bar{C}+BC$
 Question 5
A bulb in a staircase has two switches, one switch being at the ground floor and the other one at the first floor. The bulb can be turned ON and also can be turned OFF by any one of the switches irrespective of the state of the other switch. The logic of switching of the bulb resembles
 A and AND gate B an OR gate C an XOR gate D a NAND gate
GATE EE 2013   Digital Electronics
Question 5 Explanation:
Truth table of XOR gate is, So, from the XOR gate truth table, it is clear that the bulb can be turned ON and also can be turned OFF by any one of the switched irrespective of the state of the other switch.

There are 5 questions to complete.