Build a OR Gate From Transistors

About: “Let the future tell the truth, and evaluate each one according to his work and accomplishments. The present is theirs; the future, for which I have really worked, is mine.” Nikola Tesla

In this guide I will show you how to build an OR gate with two transistors.

For a basic detail of how the NPN transistor is being used in this project, please see the intro message to my AND gate instructable.


Teacher Notes

Teachers! Did you use this instructable in your classroom?
Add a Teacher Note to share how you incorporated it into your lesson.

Step 1: Parts List

To build a logic OR gate you are going to need the following parts:

  • 1x Breadboard
  • 1x LED (Any color)
  • 1x 1K Ohm resistor
  • 2x 10K Ohm resistors
  • 2x NPN Transistors (I used the 2N2222)
  • 2x N.O. Push buttons
  • 6x Various length wires/Jumper wires

You will also need to know how to build a circuit based off of a schematic.

Step 2: Schematic / Truth Table

First construct the circuit from the schematic in the above image. (Please excuse my terrible drawing skills..)

Now I will show you the truth table:

A  B  OUT
0  0  0
0  1  1
1  0  1
1  1  1

This logic gate is very simple, the output will only be ON (1) if A is ON (1), B is ON (1), or both are ON (1). Otherwise it will be OFF (0).

Share

    Recommendations

    • Indoor Lighting Contest

      Indoor Lighting Contest
    • Make It Fly Challenge

      Make It Fly Challenge
    • Growing Beyond Earth Maker Contest

      Growing Beyond Earth Maker Contest

    3 Discussions

    0
    None
    gaieb

    4 years ago on Introduction

    If on when both a and b is on, then it is an and gate for that condition

    0
    None
    MudbudBeachsideHank

    Reply 4 years ago on Introduction

    Thank you :)

    My plan is to show how to make the basic logic gates, then build up to bigger things like adders and d-type flip flops. The end goal will be a guide on building an entire CPU out of transistor logic gates (except ROM and SRAM) based off of a design I am currently working on.