Editing Tetrode (section)

==How it works==
[[Image:4-1000A linear RF deck build by K5LAD.jpg|thumb|4-1000A 1 KW radial beam power tetrode in an amateur radio transmitter]]
The tetrode functions in a similar way to the [[triode]], from which it was developed.  A current through the heater or filament heats the [[cathode]], which causes it to emit electrons by [[thermionic emission]].  A positive voltage is applied between the plate and cathode, causing a flow of electrons from the cathode to plate through the two grids.  A varying voltage applied to the [[control grid]] can control this current, causing variations in the plate current.  With a resistive or other load in the plate circuit, the varying current will result in a varying voltage at the plate.  With proper [[biasing]], this voltage will be an amplified (but inverted) version of the AC voltage applied to the control grid, providing voltage [[Gain (electronics)|gain]]. In the tetrode, the function of the other grid varies according to the type of tetrode; this is discussed below.