Amplifier by their physical placement in the signal chain; a preamplifier may precede other signal processing stages, for example. The first practical electrical device which could amplify was the triode vacuum tube, invented in 1906 by Lee De Forest, which led to the first amplifiers around 1912. Today most amplifiers use transistors. The first practical device that could amplify was the triode vacuum tube, invented in 1906 by Lee De Forest, which led to the first amplifiers around 1912. Vacuum tubes were used in almost all amplifiers until the 1960s–1970s when the transistor, invented in 1947, replaced them. Today, most amplifiers
Poppet valve in intake valves a pressure differential helps open it. The poppet valve was most likely invented in 1833 by E.A.G. Young of the Newcastle and Frenchtown Railroad. Young patented his idea but the Patent Office fire of 1836 destroyed all records of it. The word poppet shares etymology with "puppet": it is from the Middle English "popet" ("youth" or "doll"), from Middle French "poupette", which is a diminutive of "poupée". The use of the word "poppet" to describe a valve comes from the same word applied to marionettes, which – like the poppet valve – move bodily in response to