John Ambrose Flemming invented diodes in 1904. Diodes consist of a plate made of two electrodes: a cathode and an anode. These electrodes permit the surge of the current in a single direction. In addition, the electrodes can repair/convert alternating current to direct current.
Lee de Forest invented triodes in1906, just two years after Flemming invented the diode. Triodes consist of three electrodes and contain a cathode and an anode. Triodes also have a grid that consists of a screen electrode together with the cathode and anode. The grid varies from positive to negative so it has an effect on the surge of electrons from anode to cathode, thus manipulating the flow.
Albert Wallace Hull invented tetrode vacuum tubes in 1926. Tetrodes are secondary grid devices with four electrodes, established when triode reliability fluctuated during use in early radio sets. The issue was solved because tetrodes increased intensification of energy at high rates of recurrence. An additional modification is the beam tetrode, which utilizes distinctive design methods and shaped plates. The plates center the electrons as they form the beam, concentrating it on certain parts of the anode, thus making the device more efficient.
Bernard D. H. Tellegen invented the pentode in 1928. The pentode, which has five electrodes, was established when there were problems with tetrodes. Tetrodes were incapable of permitting the electrons to reach the cathode (grid) due to inadequate energy. The pentode is a suppressor grid, which drives the electrons that have fled to the anode so the electrons can be evoked.