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Introduction

Questions about transistors! You might be thinking, “Transistors? Aren’t those just switches?” Indeed, they are tiny electronic switches—but it’s precisely these switches that make our phones, computers, and all kinds of smart devices so powerful. Today, I’ll walk you through, step by step and in the simplest way, to understand: What exactly is a transistor? How do you use it? What does its symbol look like? How many “inhabitants” does it occupy inside a CPU? And what role will it play in the future?

Table of Contents

• What is a transistor
  
• How does a transistor work
  
• Transistor symbol
  
• Several classic ransistor circuits
  
• Transistor connection diagram
  
• Schematic diagram of transistor
  
• How many transistors in a CPU
  
• How many transistors in a processor
  
• What is the Transistor size?

What is a transistor

First, let’s tackle the first question: “What is a transistor?” It’s simple—a transistor is a tiny magic switch that combines “on” and “off” for electric current. When you apply voltage to its gate (Gate/B), it conducts; remove the voltage, it cuts off. But don’t stop there—it’s more than just a switch. It can also amplify signals, boosting a tiny current into a larger one we need. That means it can serve not only as a switch, but also as an “amplifier”!

How does a transistor work

Okay, now let’s talk about “how does a transistor work.” Transistors fall into two main types: BJT (Bipolar Junction Transistor) and FET (Field-Effect Transistor). A BJT has three legs—emitter (E), base (B), and collector (C). You send a tiny bit of current into the base, and that controls a much larger current flowing from collector to emitter—just like using a small valve to regulate a big water pipe. FETs are even cooler: they include MOSFETs, JFETs, and so on. You only need a voltage to open or close their channel, like lifting or lowering a sluice gate on a canal. With their high input impedance and low power consumption, they’re perfect for the massive transistor arrays inside modern chips.

Transistor symbol

In circuit schematics, the transistor symbol is your navigation landmark:

• BJT: looks like a trident, with the arrow showing NPN or PNP
• MOSFET: gate, drain, source, body—all marked with a little box or arrow
• IGBT, JFET: even more distinctive—after seeing the various variants a few times, you’ll recognize them instantly.  

Once you’ve mastered these symbols, you can breeze through any schematic diagram of transistor with ease.

Several classic ransistor circuits

So, what transistor circuits do you actually see in real life? Let’s talk about a few classics:

• Common-emitter / common-source amplifiers:BJT’s common-emitter and MOSFET’s common-source stages are the go-to workhorses for boosting small signals;  
• Emitter / source followers: The output “follows” the input—perfect for impedance matching and voltage buffering;  
• Switching circuits: In the digital world, the transistor is a fast on/off “switch worker,” building logic gates and voltage-regulation circuits;  
• Differential pairs & current mirrors: Transistors “team up” to boost linearity and stability.

Master these transistor circuit basics, and you’ll be ready to DIY your own electronic creations!  

At Jinxinyang, you can find all these classics at great prices—and we even offer free samples.

Transistor connection diagram

Now that we’ve covered circuits, do you know how transistor pins are wired? Let’s take a look:

The emitter/source is usually tied to ground or the power rail;  
The base/gate needs a bias resistor or capacitor;  
The collector/drain connects to the load or the power supply.  

Little details matter: keep decoupling capacitors close to the device and lay out the ground plane properly to ensure a stable, efficient circuit.

Schematic diagram of transistor

When you draw a full schematic diagram, you’ll see all kinds of symbols, connections, and annotations that help you understand the structure:

The bias network in an amplifier circuit;  
The pull-up/pull-down resistors in a switching circuit;  
The cross-connections in a differential pair;  
The PMOS/NMOS pairing in a CMOS inverter.  

Getting familiar with schematics is like reading an ID card—you’ll never get lost in PCB design again, and every component will be clear at a glance.

How many transistors in a CPU

That’s a great question—you’re probably wondering, “how many transistors in a CPU?” The answer is: today’s CPUs push transistor counts through the roof. A typical smartphone has tens of billions, and desktop-level chips are even more outrageous:

• Apple M1 (5 nm): 8.5 billion;  
• Apple M3 Pro (3 nm): 13.4 billion;  
• Intel Core i9-14900K (Intel 4): 14.7 billion;  
• AMD Ryzen 9 7950X (5 nm): 55 billion.

That’s right—as tiny as a chip is, its “transistor town” stacks up into a whole city!

How many transistors in a processor

So, how many transistors are in a processor? It’s not just CPUs—it also includes MCUs, DSPs, and AI accelerators:

• MCU:Hundreds of thousands to a few million transistors, used for simple control;  
• DSP: Millions to tens of millions of transistors, used for audio and video processing;  
• AI accelerators:Tens of billions—even hundreds of billions of transistors, dedicated to running deep learning models.

From embedded control to supercomputing acceleration, the transistor counts of different processors vary wildly.

What is the Transistor size?

Finally, do you want to know how big a transistor is? The following table shows the evolution of transistor size.

Era	Process Node	Transistor Size	Comparison
1950s	Discrete Transistors	~10,000 nm (10 µm)	Grain of sand
1971	Intel 4004 CPU	10,000 nm (10 µm)	Human hair (~75 µm)
2000	Pentium 4	180nm	Red blood cell (~7 µm)
2014	iPhone 6	20nm	Influenza virus (~100 nm)
2023	Apple M2	3nm	DNA helix (~2.5 nm)

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FAQ

How many transistors did the first generation CPUs have?

The first generation of CPUs (Intel 4004) contained only 2,300 transistors, but today’s high-end chips have exceeded 100 billion transistors, and computing power has increased by more than 10 million times!

What is the smallest processor in the world?

Currently, the smallest processor in the world is IBM's "smaller than a grain of salt" microchip (released in 2021), which measures only 0.3mm × 0.3mm, smaller than a grain of salt, but is fully functional and can perform basic computing tasks.