Electronic lamp

Electron tube is vacuum device, which produces a current in the emission of electrons from a heated cathode (effect Edison).
Electronic lamp consists of a glass or metal container, which creates a high vacuum (pressure 10-7 mm RT. century), with two main electrodes (cathode and anode)and one or several intermediate electrodes, called nets.
Two-electrode lamp (diode, or kenotron) of the grid has not. If between the anode and cathode lamp applying a DC voltage, current is formed. The current depends on the degree of intensity of cathode and anode voltage, maximum current is limited to the number of electrons emitted by the cathode per unit time, and is called saturation. Saturation current depends on the temperature of heating the cathode. Current in a lamp can be carried in one direction only (from the anode to the cathode), as only on the cathode generation of free charge carriers - electrons. In this regard, kenotron widely used as an AC adapter.
Three-electrode lamp (triode) has one net - a management, which (between grid and cathode) is served potential from an independent source. From the sign and magnitude of the potential on the net (at constant stress of heat and anode) is the force anode current. In this regard, the triode provides an opportunity to strengthen in the anode circuit voltage fluctuations, served on the net. Triode used in amplifiers, making up the bulk of devices for registration of action potentials (ECG, EEG and other). Three-electrode lamp is also used in the generator of the electrical fluctuations of the underlying device of equipment for high-frequency electrotherapy (diathermy, inductothermy, UHF-therapy and others). There are also electronic lamp with two (tetrode) and three (pentode) or more grids. The nearest to the cathode grid is the Manager, the rest of the subsidiary are used to improve the performance of the lamp.