In its simplest form, a suppressor grid is interposed between the screen grid and the anode (plate) of a tetrode, turning it into a pentode.
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.
The purpose of inserting suppressorgrid is avoiding secondary emission occurs in tetrode that reduce plate current, as seen on b-c curve from tetrode characteristic.
Suppressorgrid has negative voltage with respect to the others electrode because it connected directly to cathode.
By applying suppressorgrid, its negative voltage will push back secondary electron going back to plate and by this way dicreament of plate current will avoid to produce flat plate characteristic as seen of Figure 24.
Feeds |
Contact