Metal rectifier

A cuprous oxide rectifier is an obsolete, no longer used rectifier based on the semiconducting copper (I ) oxide (common name: cuprous oxide ). In order to delineate the electrolytic rectifiers then also used, based electrolytes the umbrella term dry rectifier was also common. They are among the first industrially used semiconductor devices.

History

Cuprous oxide rectifiers were produced on a large scale since about 1925. For performance applications, they were soon replaced by selenium rectifier, later based on silicon germanium and diode rectifier. Until the 1950s they were still used in measuring rectifiers, today they have no application.

The term diode is unusual for cuprous oxide rectifier, although they are similar in structure and use the same operating principles as a metal -semiconductor junction for rectification. At that time, however, was the term diode primarily the thermionic diode, a special electron tube, understood.

Construction

A single element consisting of a cuprous oxide on one side with copper ( I) oxide -coated copper plate, which has a diameter of one, depending on the current carrying capacity of up to about 40 mm. Several such sheets are connected together by stacking, by means of contact springs and interposed lead or zinc discs in series, or rectifiers. A series circuit was necessary because of only a few volts amount flyback voltage already a rectified voltage from about 10 volts.

Use

One of the advantages of the cuprous oxide rectifier is the low locks or forward voltage of 0.2-0.35 V, depending on the production technology or the specific type of material .. For this reason, they were until the middle of the 20th century used as a measurement rectifier for the AC and in particular for AC measurement using moving coil instruments. Here also their relation to the germanium diodes have been available in the 1950 years high overload was crucial. In subsequent years, cuprous oxide rectifiers were replaced by the most silicon-based Schottky diodes.

The internal resistance in the flow direction of a cuprous oxide - element is between 3 Ω and 30 Ω at typical current densities of 100 mA/cm2, so that large elements were necessary for larger currents. The small reverse voltage cascaded made ​​arrangements required. So you used for higher voltages at a current of a few milliamperes often plastic tube, in which a plurality of round oxidized copper discs were stacked, similar in structure to a selenium rod.

The reverse current of the cuprous oxide elements is relatively large and strongly temperature dependent.

Single cuprous oxide rectifier ( Graetz bridge ); the design was also called " cockchafer "

Individual parts of a cuprous oxide rectifier: copper washers with oxide layer, dark slices of hard paper isolate the bow spring

Kupferoxydulgleichrichter approximately 0.5 A / 12 V