You are given the circuits as shown in figure, which consist of NAND gates. Identify the logic operation carried out by the two circuits.

Options

A. OR gate and an AND gate respectively.
B. AND gate and NOT gate respectively.
C. AND gate and an OR gate respectively.
D. OR gate and NOT gate respectively.

Answer

A

Explanation

OR gate and an AND gate respectively.

This type of gate behaves like NOT gate.
So, `y_(1)=barA and y_(2)=barB`

`therefore Y=barA*barB`
`therefore Y=barbarA+barbarB` (de-morgon theorem)
`therefore Y=A+B[because barbarA=A and barbarB=B]`
`therefore` This combination behaves as .OR. gate. In second combination output of first NAND gate `Y.=bar(A*B)`. Now in second NAND input is shorted so it behaves like NOT gate so output `Y=barY.=barbar(A*B)=A*B` which is AND gate.