Vacuum tube: Difference between revisions

In electronics the '''vacuum tube''' or '''thermionic valve''' (outside the USA) is a device generally used to amplify, modify or control a signal. Mostly the vacuum tube has been replaced by much smaller, more reliable and less expensive solid state technology. Tubes are still used in several specialized applications such as audio systems and high power RF transmitters.<ref name ="vtbet">[{{Cite web |url=https://www.eduinblog.com/vacuum-tube-basic-electronics-tutorial/ |title=Vacuum tube – Basic electronics tutorial] |accessdate=2019-06-07 |archiveurl=https://web.archive.org/web/20190607152629/https://www.eduinblog.com/vacuum-tube-basic-electronics-tutorial/ |archivedate=2019-06-07 |url-status=dead }}</ref>

Simply put vacuum tubes are arrangements of electrodes in a vacuum, (except for some special-purpose tubes which use a gas in the envelope) within an insulating, temperature-resistant envelope, (most often of glass). The electrodes are attached to leads which pass through the envelope via an air tight seal which are designed to plug into a tube socket for easy replacement. A filament (the cathode) is heated so that it releases electrons into the vacuum (thermionic emission). These are drawn to a metal plate (the anode) inside the envelope. Another electrode (the grid) is placed between the filament and plate. A [[voltage]] applied to the grid will control the plate plate [[current]].<ref name ="vtbet"/>