The encyclopedia · Engineering & Operations · Technical decision · 1947–1951
Bell Labs replaced hot vacuum tubes with a solid sliver of germanium
The 1947 point-contact transistor amplified a signal with two gold contacts on germanium, a tiny solid-state replacement for vacuum tubes.
Bell Labs (AT&T)
the move
Every electronic device of the 1940s ran on vacuum tubes, which amplified a signal by heating a filament in a glass bulb. They were big, fragile, slow to warm up and hungry for power, so the sheer size of a computer was governed by the tubes inside it.
In 1947, at AT&T's Bell Labs, John Bardeen and Walter Brattain, working under the direction of William Shockley, demonstrated the first semiconductor amplifier: the point-contact transistor, two gold contacts pressed against a sliver of germanium.
A current through one contact regulates the current through the other, so a small input produces a large output — an amplifier with no filament, no glass and almost no heat. The device worked in a solid crystal, giving a voltage gain and amplifying the input signal up to 100 times.
Here was a way to make electronics smaller, cooler and far more reliable simply by choosing a different material and mechanism.
why it works
- A solid-state device needs no hot filament, so it consumes far less power and produces far less heat.
- With no glass and no moving parts it is far smaller, tougher and more reliable than a vacuum tube.
- A tiny amplifier that is cheap to make lets a machine use thousands of them, which is what makes a computer possible.
- The mechanism works because a small field controls a large flow, so it amplifies internally rather than by brute force.
what transfers
When a component is the bottleneck, change the physics of the component rather than the product around it — a smaller, more efficient base unit multiplies everything built on top.
what came after
The transistor made modern electronics possible, shrinking computers from rooms full of tubes into the devices everyone carries. Bell Labs' work earned the 1956 Nobel Prize in Physics, and the transistor — developed further into the junction transistor and then the integrated circuit — is the basis of the entire digital economy.
references
spotted an error? The archive wants to know.