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GATE-2012 ECE Q7 (digital)

Posted By Krishna Sankar On January 23, 2013 @ 6:23 am In GATE | No Comments

Question 7 on digital from GATE (Graduate Aptitude Test in Engineering) 2012 Electronics and Communication Engineering paper.

Q7. The output Y of a 2-bit comparator is logic 1 whenever the 2 bit input A is greater than 2 bit input B. The number of combinations for which output is logic 1 is

(A) 4

(B) 6

(C) 8

(D) 10

Solution

Let’s write all the 16 possible combinations of A and B and count the number of times A is greater than B. Can easily see that the count is 16.

A B Out
0 0 0
0 1 0
0 2 0
0 3 0
1 0 1
1 1 0
1 2 0
1 3 0
2 0 1
2 1 1
2 2 0
2 3 0
3 0 1
3 1 1
3 2 1
3 3 0
TOTAL 6

Alternately, pick each value of A and count the number of instances when A is greater than B. The count is 0 + 1 + 2 + 3 for A = 0,1,2,3 respectively.

Based on the above, the right choice is (B) 6

 

References

[1] GATE Examination Question Papers [Previous Years] from Indian Institute of Technology, Madras http://gate.iitm.ac.in/gateqps/2012/ec.pdf [1]

 

 


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