Published by: BhumiRaj Timalsina
Published date: 30 Jun 2021
Those gates which can be combined together to produce basic gates are known as universal gates. NAND and NOR gates are two universal gates.
1)NOT gate:
NOT gate can be realized using a single input NAND gate.
Logical diagram:
Fig: NAND as NOT
Truth table
| A | X=A’ |
|---|---|
| 0 | 1 |
| 1 | 0 |
2)AND gate:
AND gate can be realized using two NAND gates.
Logical diagram:
Fig: NAND as AND
Truth table
| A | B | AB |
|---|---|---|
| 0 | 0 | 0 |
| 0 | 1 | 0 |
| 1 | 0 | 0 |
| 1 | 1 | 1 |
3)OR gate:
OR gate can be realized using three NAND gates.
Logical diagram:
Fig: NAND as OR
Truth table
| A | B | A+B |
|---|---|---|
| 0 | 0 | 0 |
| 0 | 1 | 1 |
| 1 | 0 | 1 |
| 1 | 1 | 1 |
1)NOT gate:
NOT gate can be realized using a single input NOR gate.
Logical diagram:
Fig: NOR as NOT
Truth table
| A | X=A’ |
|---|---|
| 0 | 1 |
| 1 | 0 |
2)OR gate:
OR gate can be realized using two NOR gates.
Logical diagram:
Fig: NOR as OR
Truth table
| A | B | A+B |
|---|---|---|
| 0 | 0 | 0 |
| 0 | 1 | 1 |
| 1 | 0 | 1 |
| 1 | 1 | 1 |
2)AND gate:
AND gate can be realized using three NOR gates.
Logical diagram:
Fig: NOR as AND
Truth table
| A | B | AB |
|---|---|---|
| 0 | 0 | 0 |
| 0 | 1 | 0 |
| 1 | 0 | 0 |
| 1 | 1 | 1 |
Hence, all three gates can be obtained from NOR and NAND gates. So, they are called universal gates.