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|The pentode has been invented to reduce the secondary emission phenomenon
by adding a third grid called suppressor which, by its negative voltage, will push back
the electrons coming from the plate..
The suppressor grid is usually at the same voltage as the cathode some times through an internal wiring in the tube.
The pentode allows a much higher gain than a triode. It is also much better in a high-frequency design allowing a wider bandwidth.
|As a tetrode, the curve is nearly flat over a certain plate voltage. the suppressor grid linearises the curve at voltages close to the screen voltage.|
|A pentode, as all other tubes, should be used in its linear part to obtain a lower distorsion.|
Typical usage of a pentode.