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

Options

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

Answer

C

Explanation

First two similar gates are `NOT` gates and the third one is `NOR` gate.
The simple diagram can be shown as:

The output of gate `1 = bar(A)`
The output of gate `2 = bar(B)`
The output of gate `3`
`y = bar(bar(A)+bar(B)`
Use D-Emorgan's theorem
`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 Bollean expression of `AND` gate.
Note: We can define `NOR` gate as: The `OR` gate followed by `NOT` gate as shown.