Write the truth table for a NAND gate connected as given in figure.

Hence identify the exact logic operation carried out by this circuit.

Options

A.
B.
C.
D.

Answer

A

Explanation

Truth table:


`therefore ` True option is (A).
Second method:
`y=bar(y_(2)*y_(3))`
`therefore y= bar((A*y_(1))*(B *y_(1))) [ because y_(2)=bar(A*y_(1)), y_(3)=bar(B*y_(1))]`
`=barbar((A*y_(1))+(B*y_(1))`
`=(A*y_(1))+(B*y_(1))`
`=(A*y_(1))+(B*y_(1))`
`=A*(bar(A*B))+B*(bar(A*B))`
`=A*(barA+barB)+B*(barA+barB)`
`therefore y=A*barA+A*barB+B *barA+B *barB`
`therefore y=A*barB+B*barA" "[A*barA=0, B*barB=0]`
which is for XOR gate. Its truth table is like option (A).