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
Xiaodong Wang (electrical engineer) Xiaodong Wang (electrical engineer) Xiaodong Wang () is an information theorist and professor of Electrical Engineering at Columbia University. He earned a BS degree in electrical engineering and applied mathematics from Shanghai Jiaotong University, an MS degree in electrical and computer engineering from Purdue University, and a PhD from Princeton University in electrical engineering. He formerly served as assistant professor of Electrical Engineering at Texas A&M University before he joined Columbia as an assistant professor in January 2002. He is a Fellow of IEEE and an ISI Highly Cited author. He has won numerous prestigious awards, among them the National