pentóda

A pentode is a five-element vacuum tube, an electronic component that amplifies or switches electronic signals and electrical power. It consists of a cathode, a control grid, a screen grid, a suppressor grid, and an anode (plate). The cathode is heated, causing it to emit electrons. These electrons are then attracted to the anode, which is held at a positive voltage. The control grid, placed between the cathode and the anode, is used to modulate the flow of electrons, thus amplifying the signal. The screen grid and suppressor grid are additional grids that further refine the electron flow and reduce unwanted effects like secondary emission.

The addition of the screen grid and suppressor grid to the triode (a three-element tube) significantly improved performance. The screen grid, held at a positive voltage, reduces the inter-electrode capacitance between the control grid and the anode, increasing the tube's amplification factor and bandwidth. The suppressor grid, usually at or near cathode potential, prevents electrons that have been accelerated past the screen grid from returning to the screen grid due to secondary emission. This suppression of secondary emission is crucial for efficient operation at higher anode voltages.

Pentodes found widespread use in radio receivers, audio amplifiers, and other electronic circuits during the mid-20th century. Their ability to provide significant gain with relatively low power consumption made them a popular choice. While largely superseded by semiconductor devices like transistors and integrated circuits, pentodes are still used in some specialized high-fidelity audio amplifiers, musical instrument amplifiers, and vintage electronic equipment where their unique sonic characteristics are desired. The development of the pentode marked a significant step in the evolution of vacuum tube technology.