Tungar rectifiers

Tungar rectifiers (example 4B26) are designed to have a low voltage drop, with no need for high frequency capability. Typical uses include battery chargers. The name tungar is constructed from the tungsten cathode and the argon gas filling of these devices. The anode is constructed from graphite.

The addition of argon decreases the space charge drop, but also decreases the maximum working voltage - just a few hundred volts maximum.