Composition structure of vacuum diode

Composition structure of vacuum diode

The exterior of a vacuum diode is a metal or glass cover, and the air inside is precisely extracted to form a vacuum state. Inside the cover is a metal filament called the cathode (filament), surrounded by a metal cylinder called the anode (screen). The anode is sometimes made into a flat diode or plate shape.

After the cathode is connected to the power supply, it will heat up and emit electrons, just like water vapor on boiling water escaping from the water surface and being attracted by the positive electrode of the copper sheet, with current only flowing in this direction. But conversely, the particles on the copper sheet are not as hot, so they will not fly towards the filament.

So when there is a positive voltage, this device conducts, and when a negative voltage is applied, it turns off. The number of electrons emitted by the cathode per second determines the magnitude of the emission current. The cathode and battery are connected together to form a cathode circuit, and the current flowing through this circuit is called the cathode current.