Question

It is required to design a (two-input) logic gate, using an appropriate number, of :

(a) NAND gates that gives a 'low' output only when both the inputs are 'low'.

(b) NOR gates that gives a 'high' output only when both the inputs are 'high'

Draw the logic circuits for these two cases and write the truth table, corresponding to each of the two designs.

Answer 1

(a) The gate that gives a 'low' output only when both its input are low. is an OR gate

The required design is as follows.

| Input | | Output |
| A | B | Y |
| 0 | 0 | 0 |
| 0 | 1 | 1 |
| 1 | 0 | 1 |
| 1 | 1 | 1 |

(b) The Bate that gives a high output only when both the inputs are high is an AND gate.

The required design is as follows :

The'truth table' is as follows.

| Input | | Output |
| A | B | Y |
| 0 | 0 | 0 |
| 0 | 1 | 1 |
| 1 | 0 | 1 |
| 1 | 1 | 1 |