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Heated cathode valves - Diode -

Rectifier diode .. Electronics

Heated cathode valves

Electronic emission can be obtained in electronic valves by heating the cathode in it. The filament that is heated directly consists of a thin wire that is heated by electric current and can emit electrons.

77 - Direct heating filament and indirect heating cathode.

The surface emitting electrons is often electrically separated from the filament (77) which is in turn insulated from the tube or cathode. In such valves, a certain period of time is observed after the current is passed through the filament until the cathode reaches the operating temperature. This type is called indirect heating.

Diode

The thermoelectric diode consists of two main paths, and allows current to pass in one direction only. The path that emits electrons and is connected to the negative pole of the battery is usually called the cathode. The path connected to the positive pole of the battery is called the anode (78).

The filament is usually connected to the poles of a battery with an electromotive force that is canceled from the circuit diagrams for the sake of simplification.

If the anode is connected to the positive pole of a battery with a large electromotive force and the cathode is connected to its negative pole, we notice the attraction of electrons emitted from the cathode to the anode. These electrons pass

78 - Thermoelectric diode.

79 - A diode that works as a rectifier for alternating current.

The diode is in the form of an electric current called the anode diode current that allows electrons to pass from the cathode to the anode and does not allow them to pass in the opposite direction.

Rectifier diode

It is known that direct current passes in one direction. As for alternating current, it passes first in a specific direction, then in the other direction. The alternating current used to power the devices has a frequency of 50 oscillations per second, i.e. 50 complete cycles per second (79). If such a current is connected to the poles of the diode, we notice that the current passes only during the half cycle in which the anode is positive. As for the half cycles in which the current is negative, it is not allowed to pass, which results in a continuous pulsed current.

The single diode includes a cathode and an anode, and is called a "half-wave rectifier". As for the "full-wave rectifier" (80), it has two anodes instead of one, and is called a double diode.

80 - Full-wave rectifier.