In a digital circuit, a logic gate is a basic building block and it is used to implement a Boolean function. When there are more than one or more logic inputs, by using logic operations we get single logic output. To implement the logic gates, electronic switches are used like diodes or transistors. Electromagnetic relays, fluidic logic, optics, molecules, vacuum tubes, etc are also used.
A large number of electronic circuits are used in computers or control units to process the signal as T (True) or F (False). They are used in devices like embedded systems, ALUs, MUX and in computer memory. In microprocessors, more than 100 million gates are used.
The basic types of logic gates are:
- AND gate
- OR gate
- XOR gate
- NAND gate
- NOR gate
- XNOR gate
- NOT gate
To show a logic gate function, the truth table is used. The binary values 0 and 1 are used in the logic table. The combination of 0 and 1 is dependent on the number of inputs.
Following is an overview of all the logic gates with their symbols and truth table:
1.AND gate: It has two high inputs and one output which can be either high or low. Following is the truth table for AND gate:
| Inputs | Outputs | |
| A | B | O |
| 0 | 0 | 0 |
| 0 | 1 | 0 |
| 1 | 0 | 0 |
| 1 | 1 | 1 |
2.OR gate: It has two inputs in which one input is high, and the output is also high. Following is the truth table for OR gate:
| Inputs | Output | |
| A | B | O |
| 0 | 0 | 0 |
| 0 | 1 | 1 |
| 1 | 0 | 1 |
| 1 | 1 | 1 |
3.NOR gate: It has two low inputs, and the output is either high or low. Following is the truth table for NOR gate:
| Inputs | Output | |
| A | B | O |
| 0 | 0 | 1 |
| 0 | 1 | 0 |
| 1 | 0 | 0 |
| 1 | 1 | 0 |
4.NAND gate: It has two high inputs, and the output is either low or high. Following is the truth table for NAND gate:
| Inputs | Output | |
| A | B | O |
| 0 | 0 | 1 |
| 0 | 1 | 1 |
| 1 | 0 | 1 |
| 1 | 1 | 0 |
5.EX-OR gate: It has inputs which are either high or low and the output is either high or low. Following is the truth table for EX-OR gate:
| Inputs | Output | |
| A | B | O |
| 0 | 0 | 0 |
| 0 | 1 | 1 |
| 1 | 0 | 1 |
| 1 | 1 | 0 |
6.EX-NOR gate: It has either high or low inputs and the output will be either high or low. Following is the truth table for EX-NOR gate:
| Inputs | Output | |
| A | B | O |
| 0 | 0 | 1 |
| 0 | 1 | 0 |
| 1 | 0 | 0 |
| 1 | 1 | 0 |
7.NOT gate: It has just one input and the output will be inverse of input. Following is the truth table for NOT gate:
| Inputs | Output |
| A | O |
| 0 | 1 |
| 1 | 0 |
In the above article, A and B are the inputs and O is the output. Interested to learn more about other topics like Casimir effect, what is a reflection of light and other related concepts of Physics, please visit BYJU’S.