How To Make an OR Gate Using Diodes on Breadboard

Last updated on February 24th, 2024 at 01:51 pm

I am sure you must be familiar with an OR Gate, its Truth Table, Logic symbol, and its working. But do you know, you can build your own OR Gate on Breadboard?  So in this post, you will learn how to make an OR Gate using Diodes on a Breadboard.

**Read Similar Article: And Gate using Diodes

OR gate symbol and truth table

OR Gate Symbol

OR means “to add”. There are two inputs and one output in an OR Gate. Only when both inputs are zero, the output is zero. Output is 1 in all other cases. Given below is the truth table of an OR gate.

OR Gate truth table
OR Gate truth table

You can also watch the video below for quick reference:

Components required

  1. 1N4007 Diode X 2
  2. 1k Resistor
  3. LED
  4. 9v battery
  5. Connecting wires

If you are a beginner and want to know about breadboards in detail, read: How to Use a Breadboard in 5 Easy Steps

Circuit diagram of OR gate using diodes

OR Gate using diodes
OR Gate using diodes

Steps to make OR gate on Breadboard

Step 1: Place the two diodes on the breadboard. The N-terminal is the silver portion, and the P-terminal is the Black portion.

Step 2: Connect the N terminal of the Diodes together using wire as shown below:

Place diode on the breadboard
Place diode on the breadboard

Step 3: Connect two jumper wires, each at the respective p-terminal of the diodes indicating input Logic.

Connect two jumper wires

Step 4: Connect the Battery to the breadboard as shown.

connect the battery
connect the battery

Step 5: Connect the resistor from the n terminal of the Diodes to the Ground through LED.

Connect the resistor

Working

NOTE: When the P-terminal of a Diode is at a higher potential (>.7v) than its n-terminal, the diode acts like a short circuit. When the n terminal is at a higher potential, Diode acts as an open circuit.

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

Input A=0,B=0 ; Output =0
Input A=0,B=0 ; Output =0
Input A=0,B=0 ; Output =0 on breadboard

In this case, the p-terminal of both diodes is at 0 volts w.r.t n-terminal, which is  <.7v and acts like an open circuit. Thus no current flows from the 1k resistor, then LED to Ground. Hence there is no voltage across the LED, and it remains off i.e. 0 at the output.

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

Input A=0,B=1 output=1
Input A=0,B=1 output=1
Input A=0,B=1 output=1 on breadboard

In this case, the p-terminal of diode A is at 0 volts w.r.t n-terminal, which is  <.7v and hence acts like an open circuit. But the p-terminal of diode B is at a higher potential than its n-terminal, which is >.7v.

Thus, all current flows from 1k resistor, then LED to Ground. Hence some voltage across the LED turns on i.e. 1 at the output.

CASE 3: Input A=1, Input B= 0, Output=1 (LED is ON)

Input A=1,B=0 Output =1
Input A=1,B=0 Output =1
Input A=1,B=0 Output =1 on breadboard

In this case, the p-terminal of diode B is at 0 volts w.r.t n-terminal, which is  <.7v and hence acts like an open circuit. But the p-terminal of diode A is at a higher potential than its n-terminal, which is >.7v.

Thus all current flows from 1k resistor, then LED to Ground. Hence there is some voltage across the LED, and it turns on i.e., 1 at the output.

CASE 4: Input A=1, Input B= 1, Output=1 (LED is ON)

Input A=1,B=1; Output = 1
Input A=1,B=1; Output = 1
Input A=1,B=1; Output = 1 on breadboard
Input A=1,B=1; Output = 1 on breadboard

In this case, the p-terminal of both diodes is at a higher potential w.r.t n-terminal, which is  >.7v and hence acts like short circuits. Thus all current flows from 1k resistor, then LED to Ground. Hence some voltage across the LED turns on i.e. 1 at the output.

** Hence we get 0(LED is off) at the output only when both the inputs are 0.


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Ankit Negi

I am an electrical engineer by profession who loves to tinker with electronic devices and gadgets and have been doing so for over six years now. During this period, I have made many projects and helped thousands of students through my blog and YouTube videos. I am active on Linkedin and Facebook.

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