Transistors Changed Everything. Here’s How They Work

Transistors revolutionized the world, leading to the creation of personal computers, cell phones, and countless other electronic devices we rely on today. To grasp the significance of this technology, we must trace its origins back to the electric relays used in telegraphs during the 1800s. Telegraph lines were essentially long electrical circuits powered by batteries, which were bulky and required constant attention due to the lack of an electrical grid.

Electric relays, invented in 1835, served as the key components in these systems. Essentially, relays were switches that could turn electrical current on and off, much like a wall switch that controls a light. By using a second electric current to flip the switch, relays allowed operators to send signals over long distances, such as turning on a light in another town 50 miles away.

Though relays remain useful today, they are fundamentally simple on/off switches. To improve upon this concept, the vacuum tube was invented around 1905, paving the way for old-time radios. Vacuum tubes functioned similarly to light bulbs but with a filament that emitted electrons when heated, creating an electric current. By introducing a grid between the filament and a collector plate, the output current could be controlled, allowing for the amplification of audio signals and the development of early computers.

However, vacuum tubes had several drawbacks, including high power consumption, fragility, and their large size, which led to bulky and noisy computers. The transistor, invented at Bell Labs in 1947, addressed these issues by employing semiconductors—a material that can conduct electricity under certain conditions. Transistors eliminated the need for mechanical contacts, allowing for faster switching and more efficient power usage.

This breakthrough enabled the creation of smaller, quieter, and more reliable electronic devices, including modern computers and smartphones.