ElectronParade
The transistor is arguably the most important invention of the 20th century. It is the fundamental building block of all modern electronics, from simple radios to the processor inside your smartphone.
What Does a Transistor Do?
A transistor has three legs, and it performs two main functions depending on how you use it:
- As a Switch: It uses a tiny electrical signal to turn a much larger current on or off.
- As an Amplifier: It takes a small, fluctuating signal (like audio from a microphone) and outputs a proportionately larger version of that same signal to drive a speaker.
How It Works (Bipolar Junction Transistors)
The most common beginner transistor is the BJT (Bipolar Junction Transistor). Its three legs are:
- Collector (C): Where the main power enters.
- Base (B): The “trigger.” This is where you apply a small control signal.
- Emitter (E): Where the power exits the transistor.
The Concept: When a small amount of current is applied to the Base, it “opens the gate” and allows a much larger current to flow from the Collector through to the Emitter.
Why Not Just Use a Normal Switch?
If you want an Arduino to turn on a DC motor, the Arduino’s pins cannot provide enough power; the motor would draw too much current and destroy the microcontroller.
Instead, the Arduino sends a tiny, safe signal to the Base of a transistor. The transistor then acts as an electronic switch, allowing power from a larger, separate battery to flow through the Collector and power the motor safely.
Recommended Gear:
- Transistor Assortment Kit (NPN and PNP) - Essential for controlling high-power components.
- Small DC Hobby Motors - Perfect for practicing transistor switching circuits.