Pentode screen grid

Pentodes are sometimes operated in a triode connection, in which the screen grid is connected to the plate. In the 1950s, this mode of operation was popular in high-fidehty vacuum-tube audio power... 

Pentode Vacuum tube with five active electrodes cathode, control grid, screen grid, suppressor grid, plate. 

The suppressor grid of a pentode reduces the effects of secondary emission in the device. This attribute, thus, reduces the requirement to provide a reverse electron flow path for the screen grid power supply. The screen current requirement for a pentode may, however, be somewhat higher than for a tetrode of the same general characteristics. 

Suppressor grid The fifth grid of a pentode electron tube, which provides screening between plate and screen grid. 

In usual tetrode and pentode structures, the capacitance from screen-to-grid is approximately half the published tube input capacitance. The tube input capacitance is primarily the sum of the grid-to-screen capacitance and the grid-to-cathode capacitance. 

The type and degree of protection required in an RF amplifier against circuit failure will vary with the type of screen and grid voltage supply. Table 5.3 lists protection criteria for tetrode and pentode devices. The table provides guidelines on the location of a suitable relay that should act to remove the principal... 

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