Diodes And Diode Logic
Build Circuits With Rich
In this lesson we explore how diodes work and how they can be used to create basic logic gates. Diodes allow current to flow in only one direction, which makes them useful for building simple digital circuits.
How a Diode Works
A diode has two terminals:
- Anode (+)
- Cathode (-)
Current flows from the anode to the cathode when the diode is forward biased.
Typical silicon diodes require about 0.7V forward voltage.
When the diode is reverse biased, current does not flow.
You can think of a diode like a one-way valve or water pipe that only allows flow in one direction.
Diodes as Logic Gates
Because a diode can be ON or OFF, it can represent binary states.
| State | Voltage |
|---|---|
| OFF | 0V |
| ON | 5V |
This makes diodes useful for building simple logic gates.
OR Gate Using Diodes
The OR gate produces a HIGH output when either input is HIGH.
| A | B | Output |
|---|---|---|
| 0 | 0 | 0 |
| 0 | 1 | 1 |
| 1 | 0 | 1 |
| 1 | 1 | 1 |
In this circuit two diodes combine the inputs so that if either input is HIGH, current flows to the output LED.
NOR Gate
The NOR gate is the inverse of the OR gate.
| A | B | Output |
|---|---|---|
| 0 | 0 | 1 |
| 0 | 1 | 0 |
| 1 | 0 | 0 |
| 1 | 1 | 0 |
AND Gate
The AND gate only produces a HIGH output when both inputs are HIGH.
| A | B | Output |
|---|---|---|
| 0 | 0 | 0 |
| 0 | 1 | 0 |
| 1 | 0 | 0 |
| 1 | 1 | 1 |
NAND Gate
The NAND gate is the inverse of the AND gate.
| A | B | Output |
|---|---|---|
| 0 | 0 | 1 |
| 0 | 1 | 1 |
| 1 | 0 | 1 |
| 1 | 1 | 0 |
Lab Demonstration
In the video we build working circuits on a breadboard using:
- Silicon diodes
- Resistors
- LEDs
- Switches
The LED acts as the output indicator, showing whether the logic output is HIGH or LOW.
Try the Circuit Yourself
Interactive Simulations:
OR Gate:
NOR Gate:
AND Gate:
NAND Gate:
Watch the Lesson
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Bible Verse (KJV)
James 1:5
“If any of you lack wisdom, let him ask of God, that giveth to all men liberally, and upbraideth not; and it shall be given him.”
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