Previous GATE Questions on Logic Gates (1987 to Till Date)

1988

1.       For the circuit shown below, the output F is given by

Answer:     B

                              Solution :     https://www.youtube.com/watch?v=PvXtxYyx0VI

2.       Minimum number of 2 input NAND gates required to implement the function given below is

        a.       3

        b.      4

        c.       5

        d.      6

Answer:    B
                               Solution :    https://www.youtube.com/watch?v=pLnpil_Lp6I

1989

1.       Indicate which of the following logic gates can be used to realized all possible combinational logic functions :

        a.       OR gates only

        b.      NAND gates only

        c.       EX-OR gates only

        d.      NOR gates only

Answer:    B & D
                              Solution :  https://www.youtube.com/watch?v=zOkL4jMirYM

1993

1.       For the logic circuit shown in figure, the output Y is equal to

Answer:    B

Solution:  https://www.youtube.com/watch?v=yv328aRJc8o

2.       Boolean expression for the output of XNOR logic gate with inputs A and B is

        a.       AB’ + A’B

        b.      (AB)’ + AB

        c.       (A’ + B)(A + B’)

        d.      (A’ + B’)(A + B)

Answer:    C

Solution: https://www.youtube.com/watch?v=m0IvVDDvYtE

1994

1.       The output of a logic gate is ‘1’ when all its inputs are at logic ‘0’. The gate is either

        a.       a NAND or an EX-OR gate

        b.      a NOT or an EX-NOR gate

        c.       an OR r an EX-NOR gate

        d.      an AND or an EX-OR gate

Answer:    B

Solution:  https://www.youtube.com/watch?v=XLbC1IS__J0

1995 

1.       The output of the circuit shown in figure is equal to

Answer:    B

Solution: https://www.youtube.com/watch?v=f86allXIvS0

2.       The minimum number of NAND gates required to implement the Boolean function  A + AB’ + AB’C  is equal to

        a.       Zero

        b.      1

        c.       4

        d.      7

Answer:    A

Solution: https://www.youtube.com/watch?v=ZxI6mFEl4Hc

1997

1.       The output of the logic gate shown is 

        a.       0

        b.      1

        c.       A

        d.      A’

Answer:   D
                 Solution :     https://www.youtube.com/watch?v=k8wTh4Irumg 

1998

1.       The minimum number of 2 input NAND gates required to implement the Boolean function Z = AB’C, assuming that A, B and C are available, is

        a.       Two

        b.      Three

        c.       Five

        d.      Six

Answer:    C

                 Solution :      https://www.youtube.com/watch?v=BmAe0gRSr_U   

2000

1.       For the logic circuit shown in the figure, the required input combination (A,B,C) to make the output X = 1 is

 

        a.       1, 0, 1

        b.      0, 0, 1

        c.       1, 1, 1

        d.      0, 1, 1

Answer:    D

                 Solution :    https://www.youtube.com/watch?v=XdpX7qOFqBM

2.       For the logic circuit shown, the simplified Boolean expression for the output Y is

        a.       A + B + C

        b.      A

        c.       B

        d.      C

Answer:    C

                 Solution :    https://www.youtube.com/watch?v=DarZRBeGCdA

 2001

1.       In the figure, the LED

        a.       Emits light when both S₁ and S₂ are closed.

        b.      Emits light when both S₁ and S₂ are open.

        c.       Emits light when only of S₁ or S₂ is closed.

        d.      Does not emit light, irrespective of the switch positions.

Answer:    D

           Solution :      https://www.youtube.com/watch?v=XqDoyQ5IirY 

2002

1.       If the input to the digital circuit of the figure, consisting of a cascade of 20 XOR gates is X, then the output Y is equal to

Answer:     B

                  Solution :    https://www.youtube.com/watch?v=iRCfbhzqgOQ

2008 

1.       The logic function implemented by the following circuit at the terminal OUT is

        a.       P NOR Q

        b.      P NAND Q

        c.       P OR Q

        d.      P AND Q

Answer:    D

               Solution :   https://www.youtube.com/watch?v=cH-YodnqAt4

2.       Which of the following Boolean expression correctly represents the relation between P, Q, R and M₁?

Answer:    D

               Solution :   https://www.youtube.com/watch?v=toMIhaj1omc

2010

1.       Match the logic gates in Column A with their equivalents in Column B.

        a.       P – 2, Q – 4, R – 1, S – 3 

        b.      P – 4, Q – 2, R – 1, S – 3

        c.       P – 2, Q – 4, R – 3, S – 1

        d.      P – 4, Q – 2, R – 3, S – 1

Answer:    D

              Solution :  https://www.youtube.com/watch?v=dkREztdPw8E

2.       For the output F to be 1 in the logic circuit shown, the input combination should be

        a.       A = 1, B = 1, C = 0 

        b.      A = 1, B = 0, C = 0

        c.       A = 0, B = 1, C = 0

        d.      A = 0, B = 0, C = 1

Answer:    D

               Solution :  https://www.youtube.com/watch?v=pQAOPtOwtBk

2011

1.       The output Y in the circuit below is always ‘1’, when

        a.       Two or more of the inputs P,Q, R are ‘0’

        b.      Two or more of the inputs P,Q, R are ‘1’

        c.       Any odd number of the inputs P,Q,R is ‘0’

        d.      Any odd number of the inputs P,Q,R is ‘1’

  Answer:    B

               Solution : https://www.youtube.com/watch?v=vzqfBLVmISE

2014 

1.       The output F in the digital logic circuit shown in the figure is

 

Answer:    A

                 Solution :  https://www.youtube.com/watch?v=cIpdKO6C078

2.       In the circuit shown in the figure, if C = 0, the expression for Y is

Answer:    A

                 Solution : https://www.youtube.com/watch?v=zVTaxNYq03A