Practical No. 4

Title: To Verify the Truth Table of Universal Logic Gates

Aim

To understand the operation of Universal Logic Gates and verify their corresponding truth tables, demonstrating their capability to implement any other logic function.

Introduction

In digital electronics, basic gates like AND, OR, and NOT are fundamental. Universal Gates, however, offer a unique advantage: any Boolean function—and thus any other logic gate—can be implemented using only one type of universal gate. This simplifies circuit design and manufacturing.

The two primary universal gates are:

·         NAND Gate

·         NOR Gate

This practical explores their behavior and verifies their truth tables, demonstrating their universal property.

Procedure / Example

Example: Verifying the Truth Table of a 2-Input NAND Gate

1.     Inputs: A and B; Output: Q.

2.     With 2 inputs, there are 2² = 4 possible input combinations.

3.     Apply inputs and record outputs:

o    A = 0, B = 0 → Q = 1

o    A = 0, B = 1 → Q = 1

o    A = 1, B = 0 → Q = 1

o    A = 1, B = 1 → Q = 0

4.     Logical expression: Q = ¬(A · B)

5.     Truth Table:

A	B	Q
0	0	1
0	1	1
1	0	1
1	1	0

Exercises

1.     NAND Gate

·         Logical Symbol: (Draw standard 2-input NAND gate symbol: AND gate with a small circle at output)

·         Logical Expression: Q = ¬(A · B)

·         Truth Table:

A	B	Q
0	0
0	1
1	0
1	1

2.     NOR Gate

·         Logical Symbol: (Draw standard 2-input NOR gate symbol: OR gate with a small circle at output)

·         Logical Expression: Q = ¬(A + B)

·         Truth Table:

A	B	Q
0	0
0	1
1	0
1	1

Result / Conclusion

This practical successfully demonstrated the principles and operations of NAND and NOR gates. By systematically applying all input combinations and recording outputs, the truth tables for each universal gate were verified. These gates can implement any Boolean function, highlighting their importance as efficient building blocks in digital circuit design.