1906 – amplifier tube

In 1906, Lee de Forest invented a device he called the “audion” that became the first crude forerunner of an electronic amplifier. He added a third wire to a two electrode vacuum tube, changing the diode into a triode. The 1906 version, called the audion, had the third wire wrapped around the outside of the vacuum tube, but de Forest could use it to hear disturbances in the current causing sounds in headphones attached to the device which allowed him to detect weak radio signals using the noise. In 1908, he patented the three electrode version which used a grid inside the tube and became the first real triode which eventually led to the development of more amplification techniques with electronics. In electronic amplification when current is applied to the third wire, it modulates the current strength between the other two wires, allowing a weak signal to be transferred to a stronger signal while still retaining the same waveform.

PRECURSOR:
1855 – vacuum tube
1875 – Crookes tube
1883 – Edison effect

CONCURRENT:
1904 – Fleming valve
1908 – triode

SUBSEQUENT:
1947 – transistor
1958 – integrated circuit

Comments are closed.