Hello Mentees! Welcome to a new tutorial performed at Proteus ISIS. In today’s article, we’ll learn about the very basic pillar of Digital Logic Circuits. As the name implies, the digital logic circuits depends upon the digits and in Compute world, we use Boolean digits that are 1 and 0. Truss HIGH means 1 and LOW means 0in the world of Computer. We’ll grasp some basic information about:

- What are Logic Gates.
- What are truth Tables.
- Pre-requisites of experimentation.
- What are the types.
- How Gates are Implemented in Proteus ISIS.

Rush towards the 1st Question.

### Logic Gates

while Designing the digital system, the Basic building blocks of the system are logic gates. we define the Logic Gates as:

“Logic Gates are the electronic circuits that has one or more input and output and the output depends upon a certain logic used during the designing.”

There are some types of Logic Gates that have some types and every type is used for certain outputs according to need.

### Truth Tables

Truth Tables are Logical Tables that are important while designing the Digital Circuit. The elucidation of truth table is given below:

*“A truth table is the logical type of table that describes the Input and Output of the system at the same time and the connection between them.”*

These are useful in Boolean and mathematical operation as the relationship of the Input and Output can be understood at a glance.

the input conditions of the truth table depends upon the number of input. We decide the number of conditions through 2^n where “n” is the number of the inputs. If we have two input then we will test four conditions and A will be zero at start but changes after two conditions. Whereas, B will start from zero and change its values in every condition.

Prior to start, just have a look at some basic Components.

### LED

LED is a the Component in the Proteus ISIS presented in the Pick Library that glows only when it get some power or input from the device it is Connected to.

It has two terminal named Anode and Cathode. In some cases the LED’s one terminal is grounded.

### Logic Toggle

Logic Probes are also the Boolean devices and they are used to give the Input to logic circuits. They just have two conditions and we can switch the input from HIGH to LOW or vise versa through a small arrow presented on one side of the Logic Toggle.

We need the following Devices during the Experimentation.

### Apparatus Required

- AND Gate
- OR Gate
- NOT Gate
- LED
- Logic Toggle
- Ground Terminal
- Connecting Wires

### Types of Logic Gate

Here, we’ll discuss some basic kinds of the Logic Gates and we’ll discuss them one after the other.

- AND Gate
- OR Gate
- NOT Gate

### AND gate

The AND Gate Performs the Logical conjunction. We denote it with the Dot between the inputs and define the AND Gate as:

“AND Gateis the Logical gate that has theHIGHoutput only when both the Inputs are HIGH andLOWin all other Conditions.”

The numbers of Inputs in AND Gate are more than one i.e, >=2 and output is only one. If A , B are the Logic Inputs and Y is the Output then we denote A AND B as** A.B=Y**. The logical Symbol of AND gate is:

**Truth Table:**

A | B | A.B |

0 | 0 | 0 |

0 | 1 | 0 |

1 | 0 | 0 |

1 | 1 | 1 |

### Procedure

- Set the AND Gate at the Working area.
- Take logic LED from the Library and set it at the output.
- Insert a Ground Terminal from “Terminal Mode”.
- Take the Logic Toggle and set two toggles on each of the input.
- Pop the Play button.
- Change the Conditions of the Logic toggle one after the other according to the truth table and record the values of output.
- The working of LED shows the output is 1.

The resultant Circuit of AND gate should be as following:

### OR Gate

OR gate Performs the Disjunction logic in the Circuit. the symbol of this logic is a plus sign **“+”. **Identical to AND Gate, OR Gate also has minimum two inputs and one output. If A and B are the inputs and Y is the output of OR Gate then A OR B is denoted by **A+B=Y**.

“OR Gateis the basic logic gate that has the LOW output only when both of its inputs are low otherwise it has high output.”

The logical Diagram of OR Gate is given next:

**Truth Table:**

A | B | A+B |

0 | 0 | 0 |

0 | 1 | 1 |

1 | 0 | 1 |

1 | 1 | 1 |

### Procedure

- Get the OR gate from the Library.
- Attach Logic Toggles with the Inputs.
- Join the LED at the output.
- Add a Ground Terminal with LED.
- Hit the play button.
- Change the values of Logic Toggle according to the values in the truth table.
- Record the output in the result bar.
- The resultant Circuit of OR gate is:

### NOT Gate

In Logic Circuits, the NOR Gate performs the inversion. This is unary logic Gate that implies it has only one input and one output. The output of NOT Gate is denoted by a Bar or Complement on the symbol of the input.

If A is the input to the NOT Gate, then A’ is the output of NOR Gate.

if we look at the logical diagram, then for NOT Gate it is:

**Truth Table:**

A | B |

0 | 1 |

1 | 0 |

### Procedure

- Grab the NOT Gate from library.
- Attach LED and logic toggle at output and input respectively.
- NOT Gate has only one input. Hence give it high and low value one by one.
- Record results.

Truss today we learnt about the basic blocks of logic circuits i.e, logic gates, We learnt about the truth tables and use the logic gates in Proteus simulation. In next tutorials, we’ll use these gates to make other gates and circuits.