Lämppöjännite

Lämppöjännite is a Finnish term that translates to "heating voltage" or "filament voltage" in English. It refers to the voltage applied to the filament of certain vacuum tubes, such as thermionic valves or cathode ray tubes. The primary purpose of this voltage is to heat the filament, which in turn heats the cathode. When the cathode becomes hot enough, it emits electrons through a process called thermionic emission. These emitted electrons are then controlled and accelerated by other electrodes within the tube to perform various functions, like amplification or signal display.

The heating voltage is typically a low AC voltage, often in the range of a few volts. It is crucial for the proper operation of the vacuum tube, as insufficient voltage will lead to inadequate electron emission and a weak or non-existent signal, while excessive voltage can overheat and damage the filament, shortening the tube's lifespan. The specific heating voltage required varies depending on the type and design of the vacuum tube. Information regarding the correct heating voltage is usually specified by the tube manufacturer. In older electronic devices, like early radios and televisions, lämppöjännite was a fundamental parameter for tube functionality.