TRIODE

electronic vacuum tube with three electrodescathode, anode (plate), and control gridmounted in an evacuated metal or glass container. It has been used as an amplifier for both audio and radio signals, as an oscillator, and in electronic circuits. The triode is the fundamental form of vacuum tube, other forms such as the tetrode or pentode being produced by the introduction of additional grids. In most vacuum tubes, the control grid is the most important and critical electrode, controlling a relatively large flow of current (thus of power) by the application of a small voltage and negligible power. The control grid is normally a wire mesh that intercepts little or no current, even though it may on occasion be actually positive relative to the cathode.