Audio power amplifier inside the chassis of the main product. The audio amplifier was invented around 1912 by Lee De Forest, made possible by his invention of the first practical amplifying electrical component, the triode vacuum tube (or "valve" in British English) in 1907. The triode was a three terminal device with a control grid that can modulate the flow of electrons from the filament to the plate. The triode vacuum amplifier was used to make the first AM radio. Early audio power amplifiers were based on vacuum tubes and some of these achieved notably high audio quality (e.g., the Williamson amplifier of
Don Carpenter (electrical engineer) dynamics and for development and use of whistler-mode waves as diagnostic probes of the magnetosphere". He was elected a Fellow of the American Geophysical Union in 2002. Don Carpenter (electrical engineer) Donald L. Carpenter is a Space Scientist, Professor (Research) Emeritus in the Electrical Engineering Department at Stanford University. He co-discovered the sharp dropoff in the plasmasphere surrounding Earth. Known as co-discoverer of the “knee,” or sharp dropoff (later called the plasmapause) in the radial profile of the dense plasma cloud (later called the plasmasphere) that surrounds the Earth to typical equatorial distances of several Earth radii. Carpenter was awarded