{"id":193,"date":"2016-01-31T12:51:23","date_gmt":"2016-01-31T18:51:23","guid":{"rendered":"http:\/\/www.nano-blog.com\/?p=193"},"modified":"2022-09-02T13:15:31","modified_gmt":"2022-09-02T18:15:31","slug":"vacuum-tubes","status":"publish","type":"post","link":"http:\/\/www.nano-blog.com\/?p=193","title":{"rendered":"Vacuum Tubes"},"content":{"rendered":"

This might seem like an unusual topic for nanotechnology.\u00a0 The vacuum tube was the centerpiece of electronic advancement prior to solid state devices.\u00a0 Their application was incorporated into most electronics through the mid 1960s.\u00a0 Even today, audiophiles will tell you that the sound produced by equipment that uses vacuum tubes is superior to anything else that is currently available.\u00a0 Very high power devices also incorporate vacuum tubes.\u00a0 The fundamental concept of a vacuum tube consists of a cathode, a grid(s), and an anode in a glass tube, which had the internal gases exhausted to a hard vacuum level (less than 10-6<\/sup> Torr). \u00a0One Torr is equal to 0.00132 standard atmospherics (One atmosphere of pressure is that experienced at sea level).<\/p>\n

The principle of operation for the vacuum tube is to heat the cathode material to generate a stream of electrons that are captured by the anode.\u00a0 This current flow can be amplified by applying voltages to the grid(s).\u00a0 What started with one grid evolved into multi-grid tubes.\u00a0 There are issues with the vacuum tubes.\u00a0 The heat generated by the vacuum tubes impacts the lifetime of the cathode\u2019s emission of electrons.\u00a0 There is also a wait time until the tubes in a circuit have warmed up in order to function properly.\u00a0 Average lifetime of the tubes was roughly 1,500 hours.\u00a0 The impact of this short lifetime was a continual need to replace vacuum tubes.\u00a0 (More information can be found in Ref. 1)<\/p>\n

The advantage of semiconductors were much more than extended lifetimes.\u00a0 Semiconductor are much smaller, don\u2019t require a vacuum, which makes them more rugged.\u00a0 There is a consistency and reliability of semiconductors that vacuum tubes were unable to match.\u00a0 One negative of semiconductors is that the state changes are either on or off (digital signals).\u00a0 Vacuum tubes can provide an analogue change in signal.\u00a0 The semiconductor industry worked around this issue by creating digital to analogue and analogue to digital converters.<\/p>\n

There has been research on the development of \u201cVacuum transistors\u201d.\u00a0 [Ref. 2]\u00a0 By reducing the dimensions of the solid state device to the nano realm, the distance from the cathode to the anode becomes shorter than the mean free path of a gas molecules.\u00a0 The result is that the device can be operated in atmosphere and does not need a vacuum.\u00a0 The low current levels also required for the device to operate, works in preventing damage to the cathode that would typically occur at atmospheric pressure.\u00a0 There are more details available from NASA [Ref. 3] and other sources [Ref. 4].<\/p>\n

Where does this effort stand today?\u00a0 NASA Ames has demonstrated it in the lab.\u00a0 Some parallel work is being done at CalTech.\u00a0 The demonstration of a functioning circuit that is manufactured using mass production techniques has not been shown.\u00a0 However, this is a \u201cnano\u201d technology that is promising.\u00a0 Keep watching for future developments.<\/p>\n

 <\/p>\n

References:<\/p>\n

    \n
  1. http:\/\/www.vacuumtubes.net\/How_Vacuum_Tubes_Work.htm<\/a><\/li>\n
  2. http:\/\/spectrum.ieee.org\/semiconductors\/devices\/introducing-the-vacuum-transistor-a-device-made-of-nothing<\/a><\/li>\n
  3. https:\/\/www.nasa.gov\/ames-partnerships\/technology\/technology-opportunity-nanostructure-based-vacuum-channel-transistor<\/a><\/li>\n
  4. http:\/\/www.extremetech.com\/extreme\/185027-the-vacuum-tube-strikes-back-nasas-tiny-460ghz-vacuum-transistor-that-could-one-day-replace-silicon-fets<\/a><\/li>\n<\/ol>\n","protected":false},"excerpt":{"rendered":"

    This might seem like an unusual topic for nanotechnology.\u00a0 The vacuum tube was the centerpiece of electronic advancement prior to solid state devices.\u00a0 Their application was incorporated into [..]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[13,12],"tags":[],"class_list":["post-193","post","type-post","status-publish","format-standard","hentry","category-electronics","category-science"],"_links":{"self":[{"href":"http:\/\/www.nano-blog.com\/index.php?rest_route=\/wp\/v2\/posts\/193","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/www.nano-blog.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.nano-blog.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.nano-blog.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/www.nano-blog.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=193"}],"version-history":[{"count":1,"href":"http:\/\/www.nano-blog.com\/index.php?rest_route=\/wp\/v2\/posts\/193\/revisions"}],"predecessor-version":[{"id":194,"href":"http:\/\/www.nano-blog.com\/index.php?rest_route=\/wp\/v2\/posts\/193\/revisions\/194"}],"wp:attachment":[{"href":"http:\/\/www.nano-blog.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=193"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.nano-blog.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=193"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.nano-blog.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=193"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}