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


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



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




1995 

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

Answer:    B


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



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


13 comments:

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  4. gate paper 2010 ,question no 2 is wrong. output of three input xnor gate is 1 ,when there are odd no of 1 input.

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