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
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