The Diode as a Rectifier

Author: E.E. Kimberly

If for the battery B of Fig. 27-1 there be substituted a source of alternating emf, a current will flow as long as that emf charges the cathode negatively. When in the other half-cycle the plate is charged negatively, no current will flow because there are no free electrons around the cold plate to migrate to the filament. Hence, the tube will conduct in one direction only and may be used as a rectifier of alternating current. For rectification of all but very small currents, the gas-filled diode is more satisfactory because of its lower effective impedance. The high-vacuum diode is suited to high-voltage (50,000 volts or more) low-current service, such as for smoke and dust precipitation and radio transmission.