In this note, we are going to explain Different Types of Logic Gates with Truth tables, symbols and Boolean expressions. The gates are NOT, AND, OR, NOR, NAND, XOR, XNOR. Welcome to Poly Notes Hub, a leading destination for engineering notes.
Author Name: Arun Paul.
Different Types of Logic Gates with Truth Table and Symbol
Logic gates are basic components of digital circuitry. They accept one or more binary inputs (0 or 1) and output a single binary value depending on a predefined logical operation. Logic gates are used in computers, processors, arithmetic circuits, memory units, and other digital systems.
There are 7 types of basic logic gates –
- NOT Gate
- AND Gate
- OR Gate
- NAND Gate
- NOR Gate
- XOR Gate
- XNOR Gate
Below we have discuss about the different types of logic gates with their symbol, truth table, and Boolean Expression –
1. NOT Gate (Inverter)
Definition: The NOT gate has one input and one output. It inverts the input:
- If input = 1 → output = 0
- If input = 0 → output = 1
Symbol of NOT Gate and How NOT Gate Works
Boolean Expression of NOT Gate
Truth Table of NOT Gate
| A | Output (NOT A) |
|---|---|
| 0 | 1 |
| 1 | 0 |
2. AND Gate
Definition: The AND gate outputs 1 only when all its inputs are 1. If any input is 0, the output becomes 0.
Symbol of AND Gate and How AND Gate Works
Boolean Expression of AND Gate
Truth Table of AND Gate
| A | B | Output (A AND B) |
|---|---|---|
| 0 | 0 | 0 |
| 0 | 1 | 0 |
| 1 | 0 | 0 |
| 1 | 1 | 1 |
3. OR Gate
Definition: The OR gate outputs 1 when at least one input is 1. If all inputs are 0, only then the output is 0.
Symbol of OR Gate and How OR Gate Works
Boolean Expression of OR Gate
Truth Table of OR Gate
| A | B | Output (A OR B) |
|---|---|---|
| 0 | 0 | 0 |
| 0 | 1 | 1 |
| 1 | 0 | 1 |
| 1 | 1 | 1 |
4. NAND Gate
Definition: NAND = NOT + AND. It gives the opposite output of AND gate. It outputs 0 only when all inputs are 1, otherwise output is 1.
Symbol of NAND Gate and How NAND Gate Works
Boolean Expression of NAND Gate
Truth Table of NAND Gate
| A | B | Output (A NAND B) |
|---|---|---|
| 0 | 0 | 1 |
| 0 | 1 | 1 |
| 1 | 0 | 1 |
| 1 | 1 | 0 |
5. NOR Gate
Definition: NOR = NOT + OR. It gives the opposite output of OR gate. It outputs 1 only when all inputs are 0, otherwise output is 0.
Symbol of NOR Gate and How NOR Gate Works
Boolean Expression of NOR Gate
Truth Table of NOR Gate
| A | B | Output (A NOR B) |
|---|---|---|
| 0 | 0 | 1 |
| 0 | 1 | 0 |
| 1 | 0 | 0 |
| 1 | 1 | 0 |
6. XOR Gate (Exclusive OR)
Definition: The XOR gate outputs 1 only when inputs are different. If inputs are the same (00 or 11), output is 0.
Symbol of XOR Gate and How XOR Gate Works
Boolean Expression of XOR Gate
or
Truth Table of XOR Gate
| A | B | Output (A XOR B) |
|---|---|---|
| 0 | 0 | 0 |
| 0 | 1 | 1 |
| 1 | 0 | 1 |
| 1 | 1 | 0 |
7. XNOR Gate (Exclusive NOR)
Definition: XNOR is the inverse of XOR. It outputs 1 when both inputs are the same.
Symbol of XNOR Gate and How XNOR Gate Works
Boolean Expression of XNOR Gate
or
Truth Table of XNOR Gate
| A | B | Output (A XNOR B) |
|---|---|---|
| 0 | 0 | 1 |
| 0 | 1 | 0 |
| 1 | 0 | 0 |
| 1 | 1 | 1 |