Copper oxide rectifier
A copper oxide rectifier is an obsolete rectifier based on the semiconducting copper (I) oxide (common name: copper oxide) , which is no longer used today . To distinguish it from the electrolyte- based electrolyte rectifiers used at the time, the umbrella term dry rectifier was also common. They are among the first industrially used semiconductor components.
history
Copper oxide rectifiers have been manufactured on a large scale since around 1925. In power applications, they were soon replaced by selenium rectifiers , later by germanium and silicon diode- based rectifiers. They were still used in measuring rectifiers until the 1950s, but today they are no longer used.
The term diode is unusual for copper oxide rectifiers, although they are similar in structure and use the same operating principles as a metal-semiconductor junction for rectification. At that time, however, the term diode primarily meant the tube diode , a special electron tube .
construction
A single copper oxide element consists of a copper disk coated on one side with copper (I) oxide , which, depending on the current carrying capacity, has a diameter of one to about 40 mm. Several such plates are connected in series by stacking them, by means of contact springs or interposed lead or zinc disks or to form bridge rectifiers . A series connection was necessary due to the reverse voltage, which is only a few volts, even for voltages from around 10 volts to be rectified.
use
One of the advantages of the copper oxide rectifier is the low lock or flow voltage of 0.2-0.35 V, depending on the manufacturing technology or the specific type of material. For this reason, they were used as measuring rectifiers for AC voltage and especially for AC current measurements by means of moving-coil measuring mechanisms until the middle of the 20th century . Their high overload capacity compared to the germanium diodes already available in the 1950s was also decisive. In the years that followed, copper oxide rectifiers were initially replaced by selenium rectifiers, later by germanium rectifier diodes and finally by silicon diodes and silicon Schottky diodes.
The sheet resistance in the direction of flow of a copper oxide element is quite high and with typical current densities around 100 mA / cm 2 large-area elements were therefore necessary for larger currents. The small reverse voltage made cascaded arrangements necessary. The copper disks, provided with an oxide layer, were stacked with intermediate layers of soft metal to form rectifiers for higher voltages. For higher voltages with a small current of a few milliamperes, a large number of the round, oxidized copper disks were stacked in plastic tubes, similar in structure to a selenium rod .
The reverse current of the copper oxide elements is relatively large and strongly dependent on temperature.
Copper oxide measuring rectifier (left) in the "Multizet" multimeter
Copper oxide bridge rectifier ("cockchafer") on a moving-coil measuring mechanism
Individual parts of a copper oxide rectifier: copper disks with an oxide layer, dark hard paper disks isolate the bow spring
Copper oxide rectifier approx. 0.5 A / 12 V.
literature
- Karl Maier: Dry rectifier, theory, structure and application . Published by R. Oldenbourg, Berlin 1938.
swell
- ↑ Helmut Nieke: About the semiconductor properties of copper oxide. XV. Copper oxide rectifier made from single crystal copper. In: Annals of Physics . tape 478 , no. 5-6 , 1969, pp. 244-250 , doi : 10.1002 / andp.19694780505 .
- ↑ Handbook for high frequency and electrical technicians ("Bartsch"), Volume II, page 130 ff.
- ↑ http://www.imn.htwk-leipzig.de/~lueders/informatik/lehrinhalte/b16_halbleiterdioden.pdf