The Invention of the Transistor
Hands On Activity: Simple Experiments With Transistors and Solid State Devices

Home Projects Experiments Warning!

John Bardeen, William Shockley, and Walter Brattain

The first transistor ever made, built by John Bardeen, William Shockley and Walter H. Brattain of Bell Labs in 1947. Original exhibited in Bell Laboratories.
Unitronic - CC 3.0
"The transistor was probably the most important invention of the 20th Century, and the story behind the invention is one of clashing egos and top secret research."

– Transistorized!, PBS

In 1906 the American physicist Lee De Forest invented the vacuum tube triode which was the first three terminal device and enabled amplification and switching of electrical signals.

The vacuum tube helped push the development of telephony, radio and computers forward a great deal. However, the metal that emitted electrons in the vacuum tubes burned out. The tubes were too big, not reliable and required so much power that big and complicated circuits took too much energy to run. In the late 1940's, big computers were built with over 10,000 vacuum tubes and occupied over 93 square meters of space.

The problems with vacuum tubes lead scientists and engineers to think of other ways to make three terminal devices. Instead of using electrons in vacuum, scientists began to consider how one might control electrons in solid materials, like metals and semiconductors.

Already in the 1920's, scientists understood how to make a two terminal device by making a point contact between a sharp metal tip and a piece of semiconductor crystal. These point-contact diodes were used to rectify signals, and make simple AM radio receivers (crystal radios). However, it took many years before the three terminal solid state device - the transistor - was discovered.

The transistor was invented in 1947 by three American physicists at the Bell Telephone Laboratories, John Bardeen, William Shockley, and Walter Brattain. The three men received the 1956 Physics Nobel Prize for their joint invention.

The transistor proved to be a viable alternative to the vacuum tube. Transistors played a pivotal role in the advancement of electronics - their small size, low heat generation, high reliability, and small power requirements made possible the miniaturization of complex circuitry such as required by computers. During the late 1960's and 1970's individual transistors were superseded by integrated circuits in which a multiple of transistors and other components (diodes, resistors, etc.) were formed on a single tiny wafer of semi conducting material.

As happens sometimes with inventors and inventions, some people claim that the invention was invented by others. Such is also the case with the invention of the transistor. Some authorities claim that the basic idea of the solid state transistor (MOS field-effect transistor) was introduced by Julius Edgar Lilienfeld in 1925, and that the harbingers of the transistor were experiments, carried out by a few scientists, involving two terminal solid state devices (crystals) during the 1920's. But the truth must be said that the first working three terminal solid state device (transistor) was invented by the guys from the Bell Laboratories.

More about this debate:
Who really invented the Transistor? - Bell Labs
Transistor Enigma
Transistorized! The History of the Invention of the Transistor - PBS
The Transistor in a Century of Electronics -
Herbert F. Matare: An Inventor of the Transistor Has His Moment -
The Road to the Transistor - Jed Margolin
Key Steps to the Integrated Circuit - C. Mark Melliar-Smith, Douglas E. Haggan, William W. Troutman
A History of the Invention of the Transistor - William Brinkman

Experiments With Transistors and Solid State Devices

First, we suggest a few simple experiments for elementary or middle school students.

1. build a simple crystal radio (links follow):
From Science Toys
From The Charles Edison Fund
From Aaron's Homepage
By Ian C. Purdie

2. Demonstrate how transistors function as switches or amplifiers (link follows):
From PBS

3. Experiment with natural crystals (links follow):
Now we suggest to follow in the steps of those scientists from the 1920's that their experiments, with crystals, paved the way for the invention of the transistor in 1947.

The American radio amateur Nyle Steiner posts on his website technical results, photographs and curve traces of several experiments in which he has demonstrably achieved oscillation with iron pyrites (crystal) and even build an AM radio transmitter. “Success with this experiment has been a very exciting experience for me as it represents the ability to build a simple homemade active semiconductor device. It is almost like making your own homemade transistor,” he states. “This is an actual realization of some very old, and esoteric 1920s experiments by Eccles, Pickard and Lossev, that were so vaguely reported in a few articles that I have often wondered if in fact it had actually been done.”

Other experiments of his show an oscillator based on zinc ferrite and an N-type negative resistance device, similar to a tunnel diode, created by touching a piece of galvanized steel wire against a piece of aluminium.

These experiments are targeted at high school students with some knowledge of electronics.

Iron Pyrites Negative Resistance Oscillator - Nyle Steiner
Zinc Negative Resistance Oscillator - Nyle Steiner
Negative Resistance Oscillator with Homemade Tunnel Diode - Nyle Steiner

4. More computer and electronics science fair projects and experiments:
Computer and Electronics Science Fair Projects and Circuits

General Transistor Links
History of The Transistor (the "Crystal Triode") - Bell System Memorial
Welcome to Mister Transistor's Web Pages
Transistors -
Bob's Virtual Transistor Museum
Electronic Component Datasheets and Data Books -


Crystal Fire: The Invention of the Transistor and the Birth of the Information Age

This substantial book, long a standard guide to photography, is so comprehensive that it serves as an excellent reference for both amateur and professional photographers.

Principles of Transistor Circuits: Introduction to the Design of Amplifiers, Receivers and Digital Circuits

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Home Fair Projects Experiments
Scientists & Inventors Science Jokes Warning!

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Last updated: February 2018
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