Which logic gate is represented by the following combination of logic gates ?

Options

A. `AND`
B. `NAND`
C. `OR`
D. `NOR`

Answer

A

Explanation

The simple diagram can be shown as

The ouput of gate `1=bar(A)`
The ouput of gate `2=bar(B)`
The ouput of gate `3`
`y=bar(bar(A)+bar(B))`
Use Demorgan's theoram
`bar(bar(A)+bar(B))=bar(bar(A)).bar(bar(B))`
Hence, `y=bar(bar(A)).bar(bar(B)), y=A.B`
This is the Boolean expression of `AND` gate.
We can define `NOR` gate as: The `OR` gate followed by `NOT` gate as shown.