tetride

A tetrode is a type of vacuum tube that contains four active electrodes. These electrodes are typically a cathode, a grid, a screen grid, and an anode. The cathode emits electrons when heated, and these electrons are then controlled by the electric fields produced by the grids and the anode. The first grid, the control grid, modulates the flow of electrons from the cathode to the anode, thus amplifying the input signal. The second grid, the screen grid, is placed between the control grid and the anode. Its purpose is to reduce the capacitance between the control grid and the anode, which improves the high-frequency performance of the tube. The anode, also known as the plate, collects the electrons and produces the output signal. Tetrodes were an important development in early electronics, offering improved performance over triodes, particularly at higher frequencies. However, they suffered from a phenomenon called "secondary emission," where electrons knocked off the anode by high-energy primary electrons could flow to the screen grid, reducing efficiency and causing distortion. This limitation was eventually overcome with the invention of the pentode, which added a fifth electrode. Tetrodes found applications in radio transmitters, receivers, and audio amplifiers.