Tetroideihin

Tetroideihin, commonly known as tetrodes, are a type of vacuum tube used in electronic amplifiers. They are distinguished by the presence of four electrodes within the glass envelope: a cathode, a control grid, a screen grid, and a plate (anode). The cathode is heated by a filament, causing it to emit electrons. These electrons are then attracted to the positively charged plate. The control grid, positioned between the cathode and the screen grid, modulates the flow of electrons. A small voltage applied to the control grid can significantly alter the current reaching the plate, thus achieving amplification. The screen grid, placed between the control grid and the plate, serves to reduce the unwanted capacitance between these two electrodes, improving the tube's performance at higher frequencies. Tetrodes were an important development in early electronics, offering higher gain and better frequency response compared to triodes. However, they suffered from a phenomenon called "secondary emission," where electrons emitted from the plate due to bombardment by primary electrons could be attracted to the screen grid, causing instability and distortion. This limitation led to the development of the pentode, which added a fifth grid to overcome this issue. Despite being largely superseded by solid-state devices like transistors, tetrodes are still found in some specialized audio amplifiers and vintage equipment.