Page 77 - Computer Science Class 11 With Functions
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A                 B                   (A + B)'
                                       0                 0                       1

                                       0                 1                       0
                                       1                 0                       0
                                       1                 1                       0
                                                  Table 3.9: Truth table for NOR gate

                                              A
                                                                            A NOR B
                                              B

                                                 Fig 3.10: Logic Diagram for NOR gate

            Again, by De Morgan's law of Boolean algebra, we know that (A + B)'= A' ● B'. So, a NOR gate may be implemented
            by negating the inputs, followed by the application of an AND gate as shown in Fig 3.12.






                          Fig 3.11: Logic Diagram for NOR gate          Fig 3.12: Logic Diagram for NOR gate

            XOR gate: The effect of the exclusive – OR (abbreviated as XOR, also denoted by ⊕) gate is defined by the equation
            A XOR B = AB' + BA'. The truth table and logic diagram for the XOR gate are shown in Table 3.10 and Fig 3.13, respectively.


                     A          B          A XOR B
                     0          0              0            A
                     0          1              1
                                                                                        ( A  ● B) + (A ●  B ) = A ⊕ B
                     1          0              1
                                                            B
                     1          1              0

                     Table 3.10: Truth table for XOR gate     Fig 3.13: Logic Diagram for XOR gate
            Note that A XOR B = 1 if and only if exactly one of A and B is equal to 1 and the other is equal to 0. If A and B have the
            same value (0 or 1), A XOR B becomes 0. An XOR gate is denoted by the symbol shown in Fig 3.14.








                                                 Fig 3.14: Logic Diagram for XOR gate
            Equivalence gate: The effect of the equivalence gate, also called exclusive NOR gate (abbreviated as X-NOR) is defined
            by the equation A  X–NOR  B  =  AꞌBꞌ  +  AB. So, an equivalence gate outputs 1 if both the inputs are same
            (either both equal to 1 or both equal to 0) and 0 otherwise. The symbol used for equivalence gate is shown in Fig 3.15.








                                                Fig 3.15: Logic Diagram for X-NOR gate





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