Selenium rectifier

<p>A selenium rectifier is a type of <a href="/facts/Metal_rectifier/5dklbDe1">metal rectifier</a>, invented in 1933. They were used in <a href="/facts/Power_supply/4A8zBRHn">power supplies</a> for electronic equipment and in high-current battery-charger applications until they were superseded by <a href="/facts/Silicon_diode/JyaoyGnk">silicon diode</a> rectifiers in the late 1960s. The arrival of the <a href="/facts/Alternator_(automotive)/PaxsaKHP">alternator</a> in some automobiles was the result of compact, low-cost, high-current silicon rectifiers.  These units were small enough to be inside the alternator case, unlike the <a href="/facts/Selenium/k975NApC">selenium</a> units that preceded silicon devices.
</p><p>The rectifying properties of selenium, amongst other semiconductors, were observed by Braun, Schuster and Siemens between 1874 and 1883. The photoelectric and rectifying properties of selenium were also observed by Adams and Day in 1876 and C. E. Fitts around 1886, but practical rectifier devices were not manufactured routinely until the 1930s. Compared with the earlier <a href="/facts/Metal_rectifier/5dklbDe1">copper-oxide rectifier</a>, the selenium cell could withstand higher voltage, but at a lower current capacity per unit area.
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Selenium rectifier open-in-new

Selenium rectifier