Lesson 5— Electronics for kids— NOT logic gate from transistors

Rahul Agarwal
2 min readMar 13, 2023

This story is part of a series. See this starting page for links to other lessons.

In this lesson we will learn what is a NOT logic gate and build it with a transistor.

In this circuit when you send electricity then the LED turns off and when you don’t send electricity the LED turns on! So the output is NOT equal to the input. This is known as a NOT logic gate. It may also be called an inverter. It is drawn as the image below. When electricity is present it is represented as 1 and when there is no electricity it is represented as 0. So if 1 is sent to the circuit (input) then the result is 0 (output) and vice versa.

NOT gate diagram and input/output
NOT gate diagram and input/output

Logic gates are very important building blocks in the electronics we see so important for us to learn. We will look at some other ones in subsequent lessons as well.

Please see previous posts for components we have already used in the past. There is no new component in this lesson.

Breadboard visual for circuit to create a NOT gate with a transistor
Breadboard visual for circuit to create a NOT gate with a transistor
Circuit diagram to create a NOT gate with a transistor
Circuit diagram to create a NOT gate with a transistor

The LED is on (output = 1) when no electricity is being sent to the base (input = 0) of the transistor.

NOT gate input=0, output=1
NOT gate input=0, output=1

When the switch is pressed electricity is sent (input = 1) to the base of the transistor and the LED turns off (output = 0).

NOT gate input=1, output=0
NOT gate input=1, output=0

Tip: Ideally you have multiple breadboards and you can save this experiment. We will reuse Lesson 4 and Lesson 5 in Lesson 6.

This story is part of a series. See this starting page for links to other lessons.

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