Multigrid vacuum tubes contain multiple wire grids placed in the electron stream to provide advanced control over the electron flow. By adding screen grids and suppressor grids, engineers overcame the high interelectrode capacitance and secondary emission limitations of simple triodes. Common examples include tetrodes, pentodes, and hexodes, which historically dominated radio frequency amplification and mixing circuits.
Heard on the job
We need a multigrid tube like a pentode for this RF amplifier stage to prevent parasitic oscillations.