Electronics | Devices, Facts, & History

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class="md-content"> <div class="md-article-container template-desktop infinite-pagination"> <div class="infinite-scroll-container article last"> <article class="article-content container-lg qa-content px-0 pt-0 pb-40 py-lg-20 content md-expanded" data-topic-id="183904"> <div class="grid gx-0"> <div class="col-auto"> <div class="topic-left-rail md-article-drawer position-relative d-flex border-right-sm border-left-sm open"> <div class="drawer d-flex flex-column open"> <div class="left-rail-section-content"> <div class="topic-left-rail-header text-truncate bg-gray-50 position-relative text-right d-flex align-items-center"> <div class="tlr-title px-20 py-15 text-left"> <em class="material-icons text-gray-400 d-lg-none" data-icon="toc"></em> <a class="font-serif font-weight-bold text-black link-blue" href="https://www.britannica.com/technology/electronics">electronics</a> </div> <button aria-label="Close" class="js-sections-close-button btn-link btn-sm btn d-lg-none position-absolute top-0 p-10 right-0" > <em class="material-icons font-26" data-icon="close"></em> </button> </div> <div class="section-content pl-10 pr-20 pl-sm-50 pr-sm-60 pl-lg-5 pr-lg-10 pt-10 pt-lg-0 bg-gray-50 clear-catfish-ad"> <div class="toc mb-20"> <div class="font-serif font-14 font-weight-bold mx-15 mb-15 mt-20"> Table of Contents </div> <ul class="list-unstyled my-0" data-level="h1"><li data-target="#ref1"><div class="pl-25"><a class="link-gray-900 w-100" href="/technology/electronics">Introduction</a></div><div class="ml-40 toc-drawer sub-toc-drawer"></div></li><li data-target="#ref34361"><div class="d-flex align-items-center"><button class="h1-link-drawer-button btn btn-xs btn-circle d-flex rounded" type="button" aria-label="Toggle Heading"><em class="material-icons font-18" data-icon="keyboard_arrow_right"></em></button><a class="w-100 link-gray-900" href="/technology/electronics#ref34361">The history of electronics</a></div><div class="ml-40 toc-drawer sub-toc-drawer"><ul class="list-unstyled" data-level="h2"><li data-target="#ref34362"><a class="w-100 link-gray-900" href="/technology/electronics#ref34362">The vacuum tube era</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref34364"><a class="w-100 link-gray-900" href="/technology/electronics/The-semiconductor-revolution">The semiconductor revolution</a><ul class="list-unstyled" data-level="h3"><li data-target="#ref233775"><a class="w-100 link-gray-900" href="/technology/electronics/The-semiconductor-revolution#ref233775">Invention of the transistor</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref233776"><a class="w-100 link-gray-900" href="/technology/electronics/The-semiconductor-revolution#ref233776">Integrated circuits</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref233777"><a class="w-100 link-gray-900" href="/technology/electronics/The-semiconductor-revolution#ref233777">Compound semiconductor materials</a></li></ul></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref34365"><a class="w-100 link-gray-900" href="/technology/electronics/Digital-electronics">Digital electronics</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref34366"><a class="w-100 link-gray-900" href="/technology/electronics/Digital-electronics#ref34366">Optoelectronics</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref34367"><a class="w-100 link-gray-900" href="/technology/electronics/Superconducting-electronics">Superconducting electronics</a></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref34368"><a class="w-100 link-gray-900" href="/technology/electronics/Superconducting-electronics#ref34368">Flat-panel displays</a></li></ul></div></li><li data-target="#ref34369"><div class="d-flex align-items-center"><button class="h1-link-drawer-button btn btn-xs btn-circle d-flex rounded" type="button" aria-label="Toggle Heading"><em class="material-icons font-18" data-icon="keyboard_arrow_right"></em></button><a class="w-100 link-gray-900" href="/technology/electronics/The-science-of-electronics">The science of electronics</a></div><div class="ml-40 toc-drawer sub-toc-drawer"><ul class="list-unstyled" data-level="h2"><li data-target="#ref34370"><a class="w-100 link-gray-900" href="/technology/electronics/The-science-of-electronics#ref34370">Valence electrons</a><ul class="list-unstyled" data-level="h3"><li data-target="#ref34371"><a class="w-100 link-gray-900" href="/technology/electronics/The-science-of-electronics#ref34371">Conduction in semiconductors</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref233980"><a class="w-100 link-gray-900" href="/technology/electronics/The-science-of-electronics#ref233980">Fabrication of semiconductors</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref34372"><a class="w-100 link-gray-900" href="/technology/electronics/The-science-of-electronics#ref34372">State of the art</a></li></ul></li></ul><ul class="list-unstyled" data-level="h2"><li data-target="#ref34373"><a class="w-100 link-gray-900" href="/technology/electronics/Basic-electronic-functions">Basic electronic functions</a><ul class="list-unstyled" data-level="h3"><li data-target="#ref34374"><a class="w-100 link-gray-900" href="/technology/electronics/Basic-electronic-functions#ref34374">Rectification</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref34375" class="has-children"><a class="w-100 link-gray-900" href="/technology/electronics/Basic-electronic-functions#ref34375">Amplification</a><ul class="list-unstyled" data-level="h4"><li data-target="#ref233778"><a class="w-100 link-gray-900" href="/technology/electronics/Basic-electronic-functions#ref233778">Using <em>n</em>-<em>p</em>-<em>n</em> transistors</a></li></ul><ul class="list-unstyled" data-level="h4"><li data-target="#ref233779"><a class="w-100 link-gray-900" href="/technology/electronics/Basic-electronic-functions#ref233779">Using MOSFETs</a></li></ul><ul class="list-unstyled" data-level="h4"><li data-target="#ref233780"><a class="w-100 link-gray-900" href="/technology/electronics/Coupling-amplifiers">Coupling amplifiers</a></li></ul></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref34376"><a class="w-100 link-gray-900" href="/technology/electronics/Coupling-amplifiers#ref34376">Oscillation</a></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref34377" class="has-children"><a class="w-100 link-gray-900" href="/technology/electronics/Switching-and-timing">Switching and timing</a><ul class="list-unstyled" data-level="h4"><li data-target="#ref233781"><a class="w-100 link-gray-900" href="/technology/electronics/Switching-and-timing#ref233781">Using transistors</a></li></ul><ul class="list-unstyled" data-level="h4"><li data-target="#ref233782"><a class="w-100 link-gray-900" href="/technology/electronics/Switching-and-timing#ref233782">Using thyristors</a></li></ul></li></ul><ul class="list-unstyled" data-level="h3"><li data-target="#ref34378"><a class="w-100 link-gray-900" href="/technology/electronics/Optoelectronic-functions">Optoelectronic functions</a></li></ul></li></ul></div></li></ul> <a class="toc-extra-link link-gray-900" href="https://www.britannica.com/technology/electronics/additional-info">References & Edit History</a> <a class="toc-extra-link link-gray-900" href="/facts/electronics">Related Topics</a> </div> <div class="tlr-media-slider pb-10 mb-30"> <a class="section-header link-gray-900 font-serif font-14 font-weight-bold mb-10 mx-10" href="https://www.britannica.com/technology/electronics/images-videos">Images & Videos</a> <div class="slider js-slider position-relative d-inline-flex align-items-center mw-100 "> <div class="slider-container js-slider-container overflow-hidden d-flex overflow-hidden text-nowrap 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They write new content and verify and edit content received from contributors.</div> </a> <div data-popper-arrow></div> </div> <span class="btn btn-link editor-link p-0 qa-byline-link font-12 "> The Editors of Encyclopaedia Britannica</span></div> <div class="last-updated font-12 font-serif"> <span class="text-gray-700"> Last Updated: <time datetime="2024-11-22T00:00:00CST" >Nov 22, 2024</time> •</span> <a class="byline-edit-history" href="https://www.britannica.com/technology/electronics/additional-info#history" rel="nofollow">Article History</a> </div></div> </div> <button class="d-flex d-lg-none btn btn-outline-blue border rounded-sm shadow-sm mobile-toc-button gtm-mobile-toc-inline-button d-none d-sm-block js-sections-inline-button module-spacing btn d-lg-none"> <em class="material-icons mr-5 ml-n10 my-n5 md-icon" data-icon="toc"></em> Table of Contents </button> <div class="d-flex d-sm-none flex-row"> <button class="d-flex d-lg-none btn btn-outline-blue border rounded-sm shadow-sm mobile-toc-button gtm-mobile-toc-inline-button js-sections-inline-button module-spacing"> <em class="material-icons mr-5 ml-n10 my-n5 md-icon" data-icon="toc"></em> Table of Contents </button> <button class="ai-ask-button btn border-2 ai-ask-button btn border-2 module-spacing btn-sm js-inline-ai-ask-button btn-outline-red-400 border-red-400 p-10 ml-5"> Ask the Chatbot a Question </button> </div> <div class="js-qf-module qf-module px-40 px-sm-20 py-15 mx-auto module-spacing font-14 bg-gray-50 rounded"> <div class="facts-list mt-10"> <div class=""> <div class="js-fact mb-10 line-clamp clamp-3"> <dl> <dt>Key People: </dt> <dd><a href="/money/Lei-Jun" topicid="2029098">Lei Jun</a></dd> <dd><a href="/biography/An-Wang" topicid="635310">An Wang</a></dd> <dd><a href="/biography/Robert-Morris-Page" topicid="438225">Robert Morris Page</a></dd> <dd><a href="/biography/Walter-Schottky" topicid="528213">Walter Schottky</a></dd> </dl> <button class="js-more-btn d-none btn btn-unstyled font-12 bg-gray-50" aria-label="Toggle more/less fact data"> <em class="js-content link-blue">(Show more)</em> </button> </div> </div> <div class=""> <div class="js-fact mb-10 line-clamp clamp-3"> <dl> <dt>Related Topics: </dt> <dd><a href="/science/physics-science" topicid="458757">physics</a></dd> <dd><a href="/money/industry" topicid="287256">industry</a></dd> <dd><a href="/technology/electronic-system" topicid="183880">electronic system</a></dd> </dl> <button class="js-more-btn d-none btn btn-unstyled font-12 bg-gray-50" aria-label="Toggle more/less fact data"> <em class="js-content link-blue">(Show more)</em> </button> </div> </div> <div class=""> <div class="js-fact mb-10 line-clamp clamp-3"> <dl> <dt>On the Web: </dt> <dd><a href="https://spie.org/samples/TT107.pdf" target="_blank">Society of Photographic Instrumentation Engineers - Introduction to Electronics</a> (Oct. 25, 2024)</dd> </dl> <button class="js-more-btn d-none btn btn-unstyled font-12 bg-gray-50" aria-label="Toggle more/less fact data"> <em class="js-content link-blue">(Show more)</em> </button> </div> <div class="text-center"> <a class="btn btn-sm btn-link p-0" href="/facts/electronics"> See all related content </a> </div> </div> </div> </div><div class="bg-gray-50 p-15 rounded module-spacing recent-news d-flex flex-column float-false"> <div> <h2 class="font-weight-bold font-14 m-0 d-inline"> News <span class="text-gray-600">•</span> </h2> <div class="recent-news-item first-recent-news-item d-inline"> <a class="font-14 gtm-ap-news-link" href="https://techxplore.com/news/2024-11-device-power-electronics-body-movements.html" rel="nofollow">Innovative device could power electronics using body movements</a> <span class="font-14 text-gray-600"> <span>•</span> Nov. 21, 2024, 4:39 AM ET (Tech Xplore) <button class="btn btn-link d-inline p-0 font-12 js-toggle-recent-news"> <span class="text-gray-500">...</span><span>(Show more)</span> </button> </span> </div> </div> <div class="rest-of-recent-news-items"> <div class="recent-news-item mt-5"> <a class="font-14 gtm-ap-news-link" href="https://techxplore.com/news/2024-11-3d-solutions-shield-electronics-electrostatic.html" rel="nofollow">3D-printed solutions shield electronics from electrostatic discharge</a> <span class="font-14 text-gray-600"> <span>•</span> Nov. 8, 2024, 4:59 AM ET (Tech Xplore) </span> </div> <button class="js-toggle-recent-news d-flex btn btn-unstyled font-14 pr-10 rounded-sm mt-10" aria-label="Toggle additional news items"> Show less <em class="material-icons" data-icon="expand_less"></em> </button> </div> </div><span class="marker before-article"></span><section data-level="1" id="ref1"><span class="marker PREMOD1 mod-inline"></span><p class="topic-paragraph"><strong><span id="ref475051"></span>electronics</strong>, branch of <a href="https://www.britannica.com/science/physics-science" class="md-crosslink autoxref " data-show-preview="true">physics</a> and electrical <a href="https://www.britannica.com/technology/engineering" class="md-crosslink autoxref " data-show-preview="true">engineering</a> that deals with the emission, behaviour, and effects of electrons and with <span id="ref194657"></span><a href="https://www.britannica.com/technology/electronic-system" class="md-crosslink ">electronic devices</a>.</p><span class="marker MOD1 mod-inline"></span><span class="marker PREMOD2 mod-inline"></span><p class="topic-paragraph">Electronics <a class="md-dictionary-link md-dictionary-tt-off mw" data-term="encompasses" href="https://www.merriam-webster.com/dictionary/encompasses" data-type="MW">encompasses</a> an exceptionally broad range of <a href="https://www.britannica.com/technology/technology" class="md-crosslink autoxref " data-show-preview="true">technology</a>. The term originally was applied to the study of <span id="ref194658"></span><a href="https://www.britannica.com/science/electron" class="md-crosslink " data-show-preview="true">electron</a> behaviour and movement, particularly as observed in the first <a href="https://www.britannica.com/technology/electron-tube" class="md-crosslink " data-show-preview="true">electron tubes</a>. It came to be used in its broader sense with advances in knowledge about the fundamental nature of electrons and about the way in which the motion of these particles could be utilized. Today many scientific and technical <a class="md-dictionary-link md-dictionary-tt-off mw" data-term="disciplines" href="https://www.merriam-webster.com/dictionary/disciplines" data-type="MW">disciplines</a> deal with different aspects of electronics. Research in these fields has led to the development of such key devices as <a href="https://www.britannica.com/technology/transistor" class="md-crosslink " data-show-preview="true">transistors</a>, <a href="https://www.britannica.com/technology/integrated-circuit" class="md-crosslink " data-show-preview="true">integrated circuits</a>, <a href="https://www.britannica.com/technology/laser" class="md-crosslink " data-show-preview="true">lasers</a>, and <a href="https://www.britannica.com/science/fiber-optics" class="md-crosslink " data-show-preview="true">optical fibres</a>. These in turn have made it possible to manufacture a wide array of electronic consumer, industrial, and military products. Indeed, it can be said that the world is in the midst of an electronic revolution at least as significant as the industrial revolution of the 19th century.</p><span class="marker MOD2 mod-inline"></span><span class="marker PREMOD3 mod-inline"></span><div class="assemblies"><div class="w-100"><figure class="md-assembly m-0 mb-md-0 card card-borderless print-false" data-assembly-id="246890" data-asm-type="video"><div class="md-assembly-wrapper card-media " data-type="video" video-id="216554"><a data-id="216554" class="gtm-assembly-link d-flex justify-content-center" style="--aspect-ratio: 16/9" href="/video/Screen-printable-electronic-ink-for-flexible-electronics/-246890"><img src="https://cdn.britannica.com/54/216554-138-870AA8A9/Screen-printable-electronic-ink-for-flexible-electronics.jpg?w=800&h=450&c=crop" alt="Conductors and insulators in flexible electronics" loading="lazy"><script type="application/json"> { "sources": [ { "file" : "//content.jwplatform.com/manifests/miXte3uF.m3u8" } ], "image": "https://cdn.britannica.com/54/216554-138-870AA8A9/Screen-printable-electronic-ink-for-flexible-electronics.jpg" ,"tracks": [ { "file" : "//assets-jpcust.jwpsrv.com/tracks/6amgxFwI", "label": "English" } ] ,"adfile": "//content.jwplatform.com/manifests/GncOvQx4.m3u8" } </script><div class="btn btn-xl btn-white btn-circle position-absolute shadow" style="top: 50%; transform: translateY(-50%)"><em class="material-icons" data-icon="play_arrow"></em></div></a></div><figcaption class="card-body"><div class="md-assembly-caption text-muted font-14 font-serif line-clamp"><span><span class="md-assembly-title font-weight-bold mr-5 d-inline font-sans-serif md-video-caption" video-control="216554">Conductors and insulators in flexible electronics</span><span>The development of screen-printable electronic ink for flexible electronics.</span><button class="js-more-btn d-none btn btn-unstyled font-12 bg-white js-content" aria-label="Toggle more/less fact data"><span class="link-blue">(more)</span></button></span></div><a class="font-14 mt-10 d-inline-block" href="/technology/electronics/images-videos">See all videos for this article</a></figcaption></figure></div></div><p class="topic-paragraph">This article reviews the historical development of electronics, highlighting major discoveries and advances. It also describes some key electronic functions and the manner in which various devices carry out these functions.</p><span class="marker MOD3 mod-inline"></span></section> <span class="marker h2"></span><section data-level="1" id="ref34361"><h2 class="h1">The history of electronics</h2> <section data-level="2" id="ref34362"><h2 class="h2">The <span id="ref194667"></span><a href="https://www.britannica.com/technology/electron-tube" class="md-crosslink " data-show-preview="true">vacuum tube</a> era</h2> <span class="marker PREMOD4 mod-inline"></span><p class="topic-paragraph"><a class="md-dictionary-link md-dictionary-tt-off eb" data-term="Theoretical" href="https://www.britannica.com/dictionary/Theoretical" data-type="EB">Theoretical</a> and experimental studies of <a href="https://www.britannica.com/science/electricity" class="md-crosslink autoxref " data-show-preview="true">electricity</a> during the 18th and 19th centuries led to the development of the first electrical machines and the beginning of the widespread use of electricity. The history of electronics began to evolve separately from that of electricity late in the 19th century with the identification of the electron by the English physicist <a href="https://www.britannica.com/biography/J-J-Thomson" class="md-crosslink " data-show-preview="true">Sir Joseph John Thomson</a> and the measurement of its <a href="https://www.britannica.com/science/electric-charge" class="md-crosslink autoxref " data-show-preview="true">electric charge</a> by the American physicist <a href="https://www.britannica.com/biography/Robert-Millikan" class="md-crosslink " data-show-preview="true">Robert A. Millikan</a> in 1909.</p><span class="marker MOD4 mod-inline"></span> <span class="marker PREMOD5 mod-inline"></span><p class="topic-paragraph">At the time of Thomson’s work, the American inventor <span id="ref194662"></span><a href="https://www.britannica.com/biography/Thomas-Edison" class="md-crosslink " data-show-preview="true">Thomas A. Edison</a> had observed a bluish glow in some of his early lightbulbs under certain conditions and found that a current would flow from one electrode in the lamp to another if the second one (<span id="ref194663"></span><a href="https://www.britannica.com/technology/anode" class="md-crosslink " data-show-preview="true">anode</a>) were made positively charged with respect to the first (<span id="ref194664"></span><a href="https://www.britannica.com/technology/cathode" class="md-crosslink " data-show-preview="true">cathode</a>). Work by Thomson and his students and by the English engineer <span id="ref194665"></span><a href="https://www.britannica.com/biography/John-Ambrose-Fleming" class="md-crosslink " data-show-preview="true">John Ambrose Fleming</a> revealed that this so-called <span id="ref194666"></span><a href="https://www.britannica.com/science/thermionic-emission" class="md-crosslink " data-show-preview="true">Edison effect</a> was the result of the emission of electrons from the cathode, the hot filament in the lamp. The motion of the electrons to the anode, a metal plate, <a class="md-dictionary-link md-dictionary-tt-off mw" data-term="constituted" href="https://www.merriam-webster.com/dictionary/constituted" data-type="MW">constituted</a> an <a href="https://www.britannica.com/science/electric-current" class="md-crosslink autoxref " data-show-preview="true">electric current</a> that would not exist if the anode were negatively charged.</p><a class="link-module shadow-sm d-block qa-quiz-module" href="/quiz/electronics-amp-gadgets-quiz" data-link-module-iframe-link=""> <img loading="lazy" src="https://cdn.britannica.com/01/128701-131-74746B98/nano-iPod-2007.jpg" alt="The iPod nano, introduced by Apple CEO Steve Jobs in San Francisco, May 2007. A revolutionary full-featured iPod that holds 1,000 songs and is thinner than a standard #2 pencil. MP3 player, music player, digital music" class="rounded-sm mr-15" width="70" /> <div class="line-clamp clamp-5"> <div class="module-title bg-green">Britannica Quiz</div> <div class="font-weight-semi-bold mt-5">Electronics & Gadgets Quiz</div> </div> </a><span class="marker MOD5 mod-inline"></span> <span class="marker PREMOD6 mod-inline"></span><p class="topic-paragraph">This discovery provided <a class="md-dictionary-link md-dictionary-tt-off mw" data-term="impetus" href="https://www.merriam-webster.com/dictionary/impetus" data-type="MW">impetus</a> for the development of electron tubes, including an improved <a href="https://www.britannica.com/technology/X-ray-tube" class="md-crosslink " data-show-preview="true">X-ray tube</a> by the American engineer <span id="ref194668"></span><a href="https://www.britannica.com/biography/William-D-Coolidge" class="md-crosslink " data-show-preview="true">William D. Coolidge</a> and Fleming’s <span id="ref194669"></span><a href="https://www.britannica.com/technology/thermionic-valve" class="md-crosslink ">thermionic valve</a> (a two-electrode vacuum tube) for use in <a href="https://www.britannica.com/topic/radio" class="md-crosslink autoxref " data-show-preview="true">radio</a> receivers. The detection of a radio signal, which is a very high-frequency <a href="https://www.britannica.com/science/alternating-current" class="md-crosslink " data-show-preview="true">alternating current</a> (AC), requires that the signal be rectified; i.e., the alternating current must be converted into a <a href="https://www.britannica.com/science/direct-current" class="md-crosslink " data-show-preview="true">direct current</a> (DC) by a device that conducts only when the signal has one polarity but not when it has the other—precisely what Fleming’s valve (patented in 1904) did. Previously, radio signals were detected by various empirically developed devices such as the “<span id="ref194670"></span><a href="https://www.britannica.com/technology/cat-whisker" class="md-crosslink ">cat whisker</a>” detector, which was composed of a fine <a href="https://www.britannica.com/technology/wire" class="md-crosslink autoxref " data-show-preview="true">wire</a> (the whisker) in delicate contact with the surface of a natural crystal of lead sulfide (galena) or some other <a href="https://www.britannica.com/science/semiconductor" class="md-crosslink " data-show-preview="true">semiconductor</a> material. These devices were undependable, lacked <a class="md-dictionary-link md-dictionary-tt-off eb" data-term="sufficient" href="https://www.britannica.com/dictionary/sufficient" data-type="EB">sufficient</a> sensitivity, and required constant adjustment of the whisker-to-crystal contact to produce the desired result. Yet these were the forerunners of today’s solid-state devices. The fact that crystal rectifiers worked at all encouraged scientists to continue studying them and gradually to obtain the fundamental understanding of the electrical properties of semiconducting materials necessary to permit the <a href="https://www.britannica.com/technology/invention-technology" class="md-crosslink autoxref " data-show-preview="true">invention</a> of the transistor.</p><span class="marker MOD6 mod-inline"></span> <span class="marker PREMOD7 mod-inline"></span><p class="topic-paragraph">In 1906 <span id="ref194672"></span><a href="https://www.britannica.com/biography/Lee-de-Forest" class="md-crosslink " data-show-preview="true">Lee De Forest</a>, an American engineer, developed a type of vacuum tube that was capable of amplifying radio signals. De Forest added a grid of fine wire between the cathode and anode of the two-electrode thermionic valve constructed by Fleming. The new device, which De Forest dubbed the <span id="ref194673"></span><a href="https://www.britannica.com/technology/Audion" class="md-crosslink " data-show-preview="true">Audion</a> (patented in 1907), was thus a three-electrode vacuum tube. In operation, the anode in such a vacuum tube is given a positive potential (positively <a class="md-dictionary-link md-dictionary-tt-off mw" data-term="biased" href="https://www.merriam-webster.com/dictionary/biased" data-type="MW">biased</a>) with respect to the cathode, while the grid is negatively biased. A large negative bias on the grid prevents any electrons emitted from the cathode from reaching the anode; however, because the grid is largely open space, a less negative bias permits some electrons to pass through it and reach the anode. Small variations in the grid potential can thus control large amounts of anode current.</p><div class="module-spacing"> <DIV class="marketing-INLINE_SUBSCRIPTION marketing-content" data-marketing-id="INLINE_SUBSCRIPTION"><style> .student-promo-banner-wrapper { container-type: inline-size; margin-bottom: 15px; } @container (min-width: 475px) { .student-promo-banner { flex-direction: row; } .student-promo-banner-img-wrapper { margin-bottom: 0; margin-right: 10px; justify-content: flex-start; } .student-promo-banner-text-wrapper { text-align: left; margin-bottom: 0px; margin-left: 10px; } .student-promo-banner-button-wrapper { margin-right: 0; } }</style> <div class="student-promo-banner-wrapper"> <div class="student-promo-banner d-flex flex-column align-items-center bg-blue rounded p-20"> <div class="student-promo-banner-img-wrapper mb-20 mr-0 d-flex justify-content-center"> <img class="rounded" style="max-width: 100px; min-width: 80px" src="https://cdn.britannica.com/marketing/BlueThistle.webp" /> </div> <div class="student-promo-banner-text-wrapper ml-0 mb-10 text-center text-white"> <div class="h2 mb-10">Get Unlimited Access</div> <div class="h4 font-weight-semi-bold">Try Britannica Premium for free and discover more.</div> </div> <div class="student-promo-banner-button-wrapper d-flex justify-content-center align-items-center ml-auto mr-auto"> <a class="btn btn-m btn-orange" href="https://premium.britannica.com/premium-membership/?utm_source=premium&utm_medium=inline-cta&utm_campaign=black-friday-2024">Subscribe</a> </div> </div> </div> </DIV></div><span class="marker MOD7 mod-inline"></span> <span class="marker PREMOD8 mod-inline"></span><p class="topic-paragraph">The vacuum tube permitted the development of radio broadcasting, long-distance telephony, television, and the first electronic digital computers. These early electronic computers were, in fact, the largest vacuum-tube systems ever built. Perhaps the best-known representative is the <a href="https://www.britannica.com/technology/computer/ENIAC#ref216044" class="md-crosslink " data-show-preview="true">ENIAC</a> (<span id="ref194674"></span><a href="https://www.britannica.com/technology/ENIAC" class="md-crosslink " data-show-preview="true">Electronic Numerical Integrator and Computer</a>), completed in 1946.</p><span class="marker MOD8 mod-inline"></span> <span class="marker PREMOD9 mod-inline"></span><p class="topic-paragraph">The special requirements of the many different applications of vacuum tubes led to numerous improvements, enabling them to handle large amounts of power, operate at very high frequencies, have greater than average reliability, or be made very compact (the size of a thimble). The <span id="ref282881"></span><a href="https://www.britannica.com/technology/cathode-ray-tube" class="md-crosslink " data-show-preview="true">cathode-ray tube</a>, originally developed for displaying electrical waveforms on a screen for engineering measurements, evolved into the television picture tube. Such tubes operate by forming the electrons <a class="md-dictionary-link md-dictionary-tt-off eb" data-term="emitted" href="https://www.britannica.com/dictionary/emitted" data-type="EB">emitted</a> from the cathode into a thin beam that impinges on a <a href="https://www.britannica.com/technology/fluoroscope" class="md-crosslink autoxref " data-show-preview="true">fluorescent screen</a> at the end of the tube. The screen emits light that can be viewed from outside the tube. Deflecting the <a href="https://www.britannica.com/science/electron-beam" class="md-crosslink " data-show-preview="true">electron beam</a> causes patterns of light to be produced on the screen, creating the desired optical images.</p><span class="marker MOD9 mod-inline"></span> <span class="marker PREMOD10 mod-inline"></span><p class="topic-paragraph">Notwithstanding the remarkable success of solid-state devices in most electronic applications, there are certain specialized functions that only vacuum tubes can perform. These usually involve operation at extremes of power or frequency.</p><div class="one-good-fact-module"> </div><span class="marker MOD10 mod-inline"></span> <span class="marker PREMOD11 mod-inline"></span><p class="topic-paragraph">Vacuum tubes are fragile and ultimately wear out in service. Failure occurs in normal usage either from the effects of repeated heating and cooling as equipment is switched on and off (thermal fatigue), which ultimately causes a physical fracture in some part of the interior structure of the tube, or from <a class="md-dictionary-link md-dictionary-tt-off mw" data-term="degradation" href="https://www.merriam-webster.com/dictionary/degradation" data-type="MW">degradation</a> of the properties of the cathode by residual gases in the tube. Vacuum tubes also take time (from a few seconds to several minutes) to “warm up” to operating temperature—an inconvenience at best and in some cases a serious limitation to their use. These shortcomings motivated scientists at <a href="https://www.britannica.com/money/Bell-Laboratories" class="md-crosslink autoxref " data-show-preview="true">Bell Laboratories</a> to seek an <a class="md-dictionary-link md-dictionary-tt-off mw" data-term="alternative" href="https://www.merriam-webster.com/dictionary/alternative" data-type="MW">alternative</a> to the vacuum tube and led to the development of the <span id="ref282883"></span><a href="https://www.britannica.com/technology/transistor" class="md-crosslink " data-show-preview="true">transistor</a>.</p><span class="marker MOD11 mod-inline"></span></section> </section><span class="marker end-of-content"></span><span class="marker after-article"></span></div> <div id="chatbot-root"></div> </div> </div> </div> <div class="ai-dialog-placeholder"></div> </div> </div> <aside class="col-md-da-320"></aside> </div> </div> </div> </div> </article></div> </div></div> </div> </main> <div id="md-footer"></div> <noscript><iframe src="//www.googletagmanager.com/ns.html?id=GTM-5W6NC8" height="0" width="0" style="display:none;visibility:hidden"></iframe></noscript> <script type="text/javascript" id="_informizely_script_tag"> var IzWidget = IzWidget || {}; (function (d) { var scriptElement = d.createElement('script'); scriptElement.type = 'text/javascript'; scriptElement.async = true; scriptElement.src = "https://insitez.blob.core.windows.net/site/f780f33e-a610-4ac2-af81-3eb184037547.js"; var node = d.getElementById('_informizely_script_tag'); node.parentNode.insertBefore(scriptElement, node); } )(document); </script>  <script> window.ap3c = window.ap3c || {}; var ap3c = window.ap3c; ap3c.cmd = ap3c.cmd || []; ap3c.cmd.push(function() { ap3c.init('ZO4siT4cLwnykPnzZWJtd3Byb2Q', 'https://engage.email.britannica.com/'); ap3c.track({v: 0}); }); ap3c.activity = function(act) { ap3c.act = (ap3c.act || []); ap3c.act.push(act); }; var s, t; s = document.createElement('script'); s.type = 'text/javascript'; s.src = "https://engage.email.britannica.com/app.js"; t = document.getElementsByTagName('script')[0]; t.parentNode.insertBefore(s, t); </script> <script class="marketing-page-info" type="application/json"> {"pageType":"Topic","templateName":"DESKTOP","pageNumber":1,"pagesTotal":9,"pageId":183904,"pageLength":1094,"initialLoad":true,"lastPageOfScroll":false} </script> <script class="marketing-content-info" type="application/json"> [] </script> <script src="https://cdn.britannica.com/mendel-resources/3-130/js/libs/jquery-3.5.0.min.js?v=3.130.14"></script> <script type="text/javascript" data-type="Init Mendel Code Splitting"> (function() { $.ajax({ dataType: 'script', cache: true, url: 'https://cdn.britannica.com/mendel-resources/3-130/dist/topic-page.js?v=3.130.14' }); })(); </script> <script class="analytics-metadata" type="application/json"> {"leg":"B","adLeg":"B","userType":"ANONYMOUS","pageType":"Topic","pageSubtype":null,"articleTemplateType":"PAGINATED","gisted":false,"pageNumber":1,"hasSummarizeButton":false,"hasAskButton":false} </script> <script type="text/javascript"> EBStat={accountId:-1,hostnameOverride:'webstats.eb.com',domain:'www.britannica.com', json:''}; </script> <script type="text/javascript"> ( function() { $.ajax( { dataType: 'script', cache: true, url: '//www.britannica.com/webstats/mendelstats.js?v=1' } ) .done( function() { try {writeStat(null,EBStat);} catch(err){} } ); })(); </script> <div id="bc-fixed-dialogue"></div> </body> </html>

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