Suppressor grid

(electronics) A grid placed between two positive electrodes in an electron tube primarily to reduce the flow of secondary electrons from one electrode to the other; it is usually used between the screen grid and the anode. Also known as suppressor.

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A grid used in pentode vacuum tubes that suppresses interference or secondary electron flow caused by electrons that bounce off or are reflected by the plate. The suppressor grid sits between the screen grid and plate (anode). By applying a voltage to the suppressor grid at or near the cathode potential, spurious current flow is contained between the plate and suppressor grid, and leakage to other elements in the tube is limited. See pentode.

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A suppressor grid is a grid used in a thermionic valve (also called vacuum tube) to suppress secondary emission. A suppressor grid is also called the antidynatron grid, as it helps to reduce the dynatron effect.

Placement

In its simplest form, a suppressor grid, typically of coarse structure, is interposed between the screen grid and the anode (plate) of a tetrode, turning it into a pentode.

Electrical connection of grid

The suppressor grid is usually connected to the cathode and more often than not, this connection is made within the glass envelope. Because the grid is negatively charged relative to both the anode and the screen grid, it repels any secondary electrons back to the anode preventing them from contributing to the screen grid current, and to any negative resistance characteristic.

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