A brief history of the transistor

If I were to ask you right now, what is the most important discovery of the XXth century, what would you say? Probably Television or the World Wide Web... But what if I tell you that the most important discovery during the XXth century is the transistor, would you believe me?

It may be hard to do so, but without this tiny piece of technology, there would be no TVs, no MRI scanners, no solar panels, no cellphones and no portable electronic devices. How did we get there? How did we make this astonishing breakthrough that changed the world and paved the way for the electronic era? In today’s article, we are going to go back in time in order to understand where the transistor comes from and the possibilities it offers!

We are in 1947, WWII just ended, the Cold War will slowly staart to impose its dogma around the world while computers are the size of a small car and need multiple people to operate them. It’s in this context that three scientists at Bell Laboratories, a research and development company owned by AT&T (American Telephone & Telegraph), were given a mission. John Bardeen, Walter Brattain and William Shockley had to replace the vacuum tube, an electronic device used to amplify or switch electric signals.

These tubes were big, consumed a lot and weren’t reliable. You had to often replace them as the heat they produced damaged themselves throughout time and made them improper for a normal use.

Bardeen and Brattain were working on an experiment to study the behavior of electrons in a semiconductor material called germanium. They had built a device called a point-contact diode, which consisted of a small piece of germanium with a fine wire attached to it. They discovered that when a voltage was applied to the wire, it caused a current to flow through the germanium, creating a signal. Shockley, who was working on a theory to explain the behavior of electrons in semiconductors, realized that the point-contact diode could be used as a switch to control the flow of electricity. He then designed a device called a junction transistor, which used two layers of germanium with impurities added to create a “p-n junction” that acted as a switch. In December 1947, Bardeen, Brattain, and Shockley demonstrated the first working transistor, which was smaller, more efficient, and more reliable than the vacuum tube. The transistor quickly became the basis for a new generation of electronic devices, including radios, televisions, and computers.

But how does it work? Well the answer is of course complex in terms of electronics but we can try to grasp the principles in an easy way. A transistor has three parts: the emitter, the base, and the collector (see scheme). When electricity flows into the base of the transistor, it allows more electricity to flow from the emitter to the collector. It’s kind of like a gatekeeper. When the gatekeeper gets a signal, it opens the gate and lets more people through. When it doesn’t get a signal, it keeps the gate closed. It either lets electricity flow or stops it, depending on whether it gets a signal. But that’s not all it does! Apart from acting like a switch it can also amplify current. When a small amount of current flows into the base of the transistor, it can control a larger amount of current flowing from the emitter to the collector. It’s like a small signal controlling a larger one. So, imagine you have a toy car that runs on batteries. The batteries produce a small amount of electricity that makes the car move. Now, if you connect a transistor to the batteries, you can use a small amount of current to control a larger amount of current that makes the car move faster. This is called amplification, and it’s one of the most important functions of a transistor. Therefore, with this tiny piece of technology, we can amplify electrical signals (microphone to speaker, LED brightness…) or control the flow of current (power supplies, light switch and most importantly computer memory). Transistors are used as switches in computer memory to store and retrieve data. In a type of computer memory called dynamic random-access memory (DRAM), each memory cell consists of a transistor and a capacitor. The transistor acts as a switch to control the charge on the capacitor, which represents a binary value of 0 or 1. You must probably know that all of our electronic devices run on binary. And these code lines contain billions of 1 and 0. So, what would we need to operate billions of binary lines? Billions of transistors!

The last processor chip made by Apple for its iPhone 14 and over, the A16 Bionic, contains 16 billion transistors. Yes. That’s right. They don’t look like the one pictured in this article as they are much, much smaller. IBM managed to produce transistors that are (only) 10 times bigger than a Silicon atom standing at an astonishing 2nm (0.0000002cm) even though the standards still remain as 7nm. Those are essential for all the devices we use in our everyday life, and I wouldn’t be able to write this article if it didn’t exist!

In conclusion, the transistor’s invention literally changed our lives. It is considered by many historians as the most important discovery of the XXth century and in recognition of their work, Bardeen, Brattain and Shockley all received the Nobel Prize in Physics in 1956. But with the reduction of their size and the improvement of their performances, how far will we go with that version of the transistor? Will it be outdated by the upcoming quantum computers? Let’s see what the coming years have to offer to us!

Hugo Lhomedet

Sources:

“Transistor” - Encyclopedia Britannica

“How Transistors Work”HowStuffWorks

“Introduction to Transistors”SparkFun Electronics

“Transistors” - Khan Academy