Researched
Vacuum Tube (Triode)
Lee de Forest’s triode amplifies and switches electrical signals with no moving parts: the basis of radio, radar and the first computers.
Open in the interactive tree →John Ambrose Fleming invented the tube diode in 1904 and Lee de Forest the triode (Audion) with a control grid in 1906. Weak signals could now be amplified and switched very fast. Tubes powered radio, television, radar and early electronic computers such as ENIAC (about 17,500 tubes), but they were bulky, hot and failure-prone.
Prerequisites
- Vacuum Pumps & Gas Laws1643-1662Tubes need a high vacuum made with vacuum pumps
- Electromagnetism1831-1865
- Incandescent Light Bulb1879Fleming's diode grew out of the Edison effect seen in light bulbs
- Electrification1882
- Discovery of the Electron1897Tubes control the flow of free electrons
Unlocks
- Broadcasting & Television1920
- EEG1924Brain signals are microvolts; tube amplifiers made recording practical
- Particle Accelerators1932
- Radio astronomy1933
- Radar1935
- Cavity Magnetron1940
- Programmable Computer1941
- Colossus Codebreaking Computer1943
- Transistor1947
- Mapping the ocean floor1957