How To Make a Not Gate using a Transistor on Breadboard

NOT GATE USING TRANSISTOR

I am sure you must be familiar with a NOT Gate, it’s Truth Table, Logic symbol, and its working. But do you know, you can build your own NOT Gate on Breadboard?  So in this post, you will learn how to make a NOT Gate using a transistor on Breadboard.

 

**Read Similar Article: And Gate using Diodes

 

What is a NOTGate?

 

Symbol of NOT Gate
Symbol of NOT Gate

 

NOT gate is a Logic Gate and called so because NOT means “Opposite”. There is only one input and one output in a  NOT Gate.  So when the input is 0, output is 1 and when the input is 1, output is 0.

 

You can also watch the video below for quick reference:

 

Truth Table:

Truth Table of NOT Gate
Truth Table of NOT Gate

 

Components required:

1. BC547 Transistor X 2

2. 1k, 100-ohm Resistor

3. LED

4. 9 Volt Battery

5. Connecting Wires

 

SCHEMATIC:

NOT Gate using Transistor
NOT Gate using Transistor

This is the circuit we are going to build on Breadboard.

1. Collector goes to +ve terminal of battery through 1k resistor

2. Logic inputs is given to base of the transistor through 100 ohm resistor.

3. Emitter goes to Ground i.e, -ve terminal of the battery.

4. Output indicator i.e LED is connected between collector and emitter(Gnd).

5. Ground- Negative terminal of the battery.

 

WORKING:

Transistor acts like a switch in this circuit. Whenever there is some threshold voltage at base, transistor acts like a closed switch from collector to emitter. And whenever there is no or less voltage then threshold voltage at the base, it acts like an open circuit from collector to emitter.

**from circuit diagram

 

CASE 1: Input A=0

In this case, there is no voltage at the base of the transistor. So it acts like an open switch from collector to emitter i.e, infinite resistance between collector and emitter. And due to this no current flow from collector to Ground. All current flow from the resistor to LED and then to ground i.e, through the path of minimum resistance. Hence LED turns on i.e, 1 at the output. 

 

CASE 2: Input A=1

In this case, there is some threshold voltage at the base of the transistor. So it acts like a closed switch from collector to emitter i.e, almost zero resistance between collector and emitter. And due to this no current flow from resistor to LED and then to ground. All current flow from collector to Ground i.e, through the path of minimum resistance. Hence LED turns off i.e, 0 at the output. 

** Hence we get 0(LED is off) at the output when input is 1 and 1(LED is ON) at the output when input is 0.

 

Simulation:

Note: Before building the circuit on a breadboard, it is first simulated on “Every circuit” app. You can download the app from here.

** The circuit is exactly similar to what is given above.

NOT gate using transistor
NOT gate using transistor

 

 

 

** Slideshow

CASE 1: Input A=1, Output=0 (LED is OFF)

CASE 2: Input A=0, Output=1 (LED is ON)

 

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Let’s Make it!

 

1. Place the transistor on Breadboard as shown in figure below. Transistor terminals from left to right: COLLECTOR, BASE, EMITTER.

**Slideshow

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2.  Connect 100-ohm Resistor from collector to +ve terminal of the battery as shown below:

**Slideshow

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3. Now connect 1k resistor from base of the transistor to the input logic.

 

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4. Now connect jumper wire at input.

 

 

5. Connect emitter to Ground i.e, -ve terminal of battery:

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6. Connect terminals of the 9v battery as shown below:

 

 

7. Now connect LED from collector(longer leg) to emitter(shorter leg) .

**Slideshow

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CASE 1: Input A=0, Output=1 (LED is ON)

 

This slideshow requires JavaScript.

 

In this case, there is no voltage at the base of the transistor. So it acts like an open switch from collector to emitter i.e, infinite resistance between collector and emitter. And due to this no current flow from collector to Ground. All current flow from the resistor to LED and then to ground i.e, through the path of minimum resistance. Hence LED turns on i.e, 1 at the output. 

 

CASE 2: Input A=1,  Output=0 (LED is OFF)

 

This slideshow requires JavaScript.

 

In this case, there is some threshold voltage at the base of the transistor. So it acts like a closed switch from collector to emitter i.e, almost zero resistance between collector and emitter. And due to this no current flow from resistor to LED and then to ground. All current flow from collector to Ground i.e, through the path of minimum resistance. Hence LED turns off i.e, 0 at the output. 

** Hence we get 0(LED is off) at the output when input is 1 and 1(LED is ON) at the output when input is 0.

 

You can also watch the video below for quick reference:

 

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