Give the basic construction of pentode

Ans:

Construction of Pentode:  Constructional details of a typical pentode are demonstrated in fig. (a)  and  fig. (b)  Pentode comprise five  electrodes  namely  a  cathode,  three  grids (suppressor grid, control grid, screen grid) and a  plate. Grid closest to the cathode is control  grid,  next  is  the  screen  grid  and  third  is  the  suppressor  grid.   Suppressor grid is generally coarser than the control grid or even screen grid mesh and is placed very close to the plate. It doesn't obstruct the flow of electrons from cathodes to anode (or plate). To keep the control grid-to-plate capacitance small extra shields are provided either within the glass envelope or external to it. In latter case the bulb is so shaped as to allow the shield to come very near to plate.