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Diode
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<p>A diode is a two-<a href="/facts/Terminal_(electronics)/CwbKGSuB">terminal</a> <a href="/facts/Electronic_component/F3NBVv4Q">electronic component</a> that conducts <a href="/facts/Electric_current/Dc1xdnUX">current</a> primarily <a href="/facts/One-way_traffic/WpXIG0BB">in one direction</a> (asymmetric <a href="/facts/Electrical_conductance/hxSt0UAj">conductance</a>). It has low (ideally zero) <a href="/facts/Electrical_resistance_and_conductance/hxSt0UAj">resistance</a> in one direction and high (ideally infinite) resistance in the other. </p><p>A <a href="/facts/Semiconductor/zFf3mGTE">semiconductor</a> diode, the most commonly used type today, is a <a href="/facts/Crystallinity/qA9S1duu">crystalline</a> piece of semiconductor material with a <a href="/facts/P%E2%80%93n_junction/CaKIdLPg">p–n junction</a> connected to two electrical terminals. It has an <a href="/facts/Exponential_function/ewlYxvR2">exponential</a> <a href="/facts/Current%E2%80%93voltage_characteristic/wft425cq">current–voltage characteristic</a>. Semiconductor diodes were the first <a href="/facts/Semiconductor_device/6W3ryr50">semiconductor electronic devices</a>. The discovery of asymmetric electrical conduction across the contact between a <a href="/facts/Crystal/e2R2mk3E">crystalline</a> mineral and a metal was made by German physicist <a href="/facts/Ferdinand_Braun/DSFrKurX">Ferdinand Braun</a> in 1874. Today, most diodes are made of <a href="/facts/Silicon/cgWx0hdr">silicon</a>, but other semiconducting materials such as <a href="/facts/Gallium_arsenide/BakLFjpp">gallium arsenide</a> and <a href="/facts/Germanium/wtoALHGs">germanium</a> are also used. </p><p>The obsolete thermionic diode is a <a href="/facts/Vacuum_tube/VHd1BNLq">vacuum tube</a> with two <a href="/facts/Electrode/251PaKX8">electrodes</a>, a heated <a href="/facts/Cathode/tqdlGayU">cathode</a> and a <a href="/facts/Plate_electrode/zAkTJdsa">plate</a>, in which <a href="/facts/Electron/L0KBo5cW">electrons</a> can flow in only one direction, from the cathode to the plate. </p><p>Among many uses, diodes are found in <a href="/facts/Rectifier/me8XDxND">rectifiers</a> to convert <a href="/facts/Alternating_current/qxICS3xa">alternating current</a> (AC) power to <a href="/facts/Direct_current/r9MNUx84">direct current</a> (DC), <a href="/facts/Demodulation/GFLGoxFl">demodulation</a> in <a href="/facts/Radio_receiver/5olDTxkg">radio receivers</a>, and can even be used for <a href="/facts/Boolean_Logic/VkCToAmg">logic</a> or as <a href="/facts/Temperature_sensor/almVTBxI">temperature sensors</a>. A common variant of a diode is a <a href="/facts/Light-emitting_diode/gE8x4MDb">light-emitting diode</a>, which is used as <a href="/facts/Electric_lighting/v3fb5WBp">electric lighting</a> and status indicators on electronic devices. </p>