Table of Contents

## Logic Gate

### Introduction

Logic Gate is a type of electronic circuit that receives one or more inputs and provides only one output.

### Concepts about Logic Gate

Logic Gate is an English word. Logic means logic, meaning it will work on rational matters. We know that computers can understand numbers 0 and 1. Logic Gate can actually understand numbers 0 and 1. The Boolean algebra, D-Morgan’s formula The logic gate is one of the things that needs to be done to bring about this whole thing. With this logic gate, the form of input and output can be understood.

### Types of Logic Gates

The logic gate can be divided into the following ways:

## Basic Logic Gate

- AND Gate
- OR Gate
- NOT Gate

Below is a diagram of the various gates where Symbol and Truth Table are given. Gate’s input is A, B, and output Q. Truth Table gives logical calculations of input and output status.

### AND Gate

- There will be two more than two inputs and one output.
- The AND value is multiplication, that is, if all inputs are 1 then its output will be 1. If one input is 0 then its output will be 0.

Let’s say two inputs A and B. If input is 1 then output is 1, then A = 0, B = 1 or A = 1, B = 0 then their output will be 0. But if A = 1, B = 1, then the output will be 1. Because all the input values here are 1. The rest is shown in the figure through the truth table.

### OR Gate

- There will be two or more than two inputs and one output.
- It will work as a sum, that is, if any input is 1, its output will be 1 otherwise the output will be 0.

Let’s say two inputs A and B. If input is 1 then output is 1, then A = 0, B = 1 or A = 1, B = 0 then their output will be 1. If A = 1, B = 1, then the output will be 1. Because all the input values here are 1. The rest is shown in the figure through the truth table.

### NOT Gate

It will have one input and one output. The output will be the opposite of the input, that is, if the input is 1 then the output will be 0.

If A = 0 then the output will be 1.If A = 1, then the output will be 0.

## Universal Gates

### NAND Gate

The NAND gate operates like an AND gate followed by a NOT gate. It acts in the method of the logical operation and followed by negation. The output is false if the inputs are true. Else the output is true.

### NOR Gate

The NOR gate is a combination of OR gate followed by a NOT gate. Its output is true if the inputs are false. Otherwise, the output is false.

## Other Logic Gate(Exclusive Gates)

### X-OR Gate

The X-OR ( exclusive-OR ) gate acts in the same way as the logical either/or. The output is true if 0ne of the input, not both, of the inputs, is true. The output is false if both inputs are false or both inputs are true. In another way of watching at this circuit is to observe that output is 1 if the inputs are various, but 0 if the inputs are the same.

### X-NOR Gate

The X-NOR (exclusive-NOR) gate is a combination X-OR gate followed by an inverter. Its output is “true” if the inputs are the same 0, and “false” if the inputs are different.

## Practical Application Of Logic Gate

During the above discussion about various digital logic gates, we have mainly discussed the design, property, and operation of them. In this section, we will look at various applications of logic gates. Their applications are appointed mainly based upon their truth table i.e. their mode of operations. In the discussion, we will look at the applications of many normal logic gates as well.

### Application Of OR Gate

Wherever the occurrence of any one or more than one event is required to detected or some actions are to take after their occurrence, in all those cases OR gates can use. It can be explained with an example. Suppose in a technical plant if one or more than one parameter overpass the safe value, some protective measures are required to be done. In that case, the OR gate is used. We are going to show this with the help of the below diagram.

The above figure is a normal schematic diagram where an OR gate is used to detect overpass of temperature or pressure and produce a command signal for the system to take required actions.

### Application Of AND Gate

There are two applications of AND gate as Enable gate and Inhibit gate. Enable gate means allowance of data by a channel and the Inhibit gate is just the reverse of that process i.e. disallowance of data through a channel. We are getting to show an enabling operation to understand it in an easier way. Suppose within the measurement of the frequency of a pulsed waveform. For metering of frequency, a gating pulse of known frequency is dispatched to enable the passage of the waveform whose frequency is to be measured. The diagram given below shows the arrangement of the explained operation.

### Application Of X-OR/X-NOR Gate

These types of logic gates are used in the generation of parity generation and checking units. The two diagrams below show the even and odd parity generator circuits respectively for four data.

With the help of these gates, the parity check operation can be also performed. The diagrams are given below show even and odd parity check.

Figure (a) shows the parity check using Ex-OR gates and figure (b) shows the parity check using Ex-NOR gates.

### Application Of NOT Gate

NOT gates are also known as an inverter because they invert the output given to them and show the reverse result. Now the CMOS inverters are generally used to build square wave oscillators that are used for generating clock signals. The advantage of using these they consume low power and their interfacing is very easy compared to other logic gates.

The above figure shows the most fundamental circuit made of ring configuration to generate a square wave oscillator. The frequency of this type of generator is given by

Where n represents the number of inverters and t_{p} shows the propagation delay per gate.

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