Lee De Forest’s 1907 Audion vacuum tube is widely credited with kickstarting the modern electronics industry in general, but it would take the much smaller, lower-power and cooler transistor to shift it into high gear.
The thermonic triode, a vacuum tube similar to the one pictured, works by using heat to modify the conductive properties of a fillament. In 1880, Thomas Edison discovered that, when a parallel current was applied to the lament circuit, the charge in the hot lament could be amplified, or cut off. Edison used his “thermonic diode” to power the first telegraph stations. The triode added a charged grid that could modify the current.
German physicist Julius Edgar Lilienfeld filed patents in the US and Canada for a field-effect transistor during the 1920s, which was intended to be a solid-state re- placement for the power-hungry, fragile thermonic triode vacuum tube (see sidebar). It was (and is) able to both act as an electronic logic gate (used in modern computer circuitry) using a two-terminal electron “channel” (with a “source” and a “drain”, and a one-terminal “gate”), and as an amplifier, able to build up the strength of a signal by using current to narrow the channel at one end; however, the materials necessary to make his invention practical would not exist for another twenty years. More…