Back to home page
Back to audio electronics page
Back to initiation page


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.

supgrid.gif (9000 octets)

Pentode Curves

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.

Back to top