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Triode Vacuum Tube

Here we show the flow of electrons from the heated cathode, through the control grid, and to the anode. The heater (red coil wrapped around the cathode) heats the cathode and the cathode, which is coated with a low work function material emits thermal electrons. The control grid usually has a repelling voltage applied to it. In this particular animation, when the control grid voltage is negative, no electrons flow through it which is a condition called cutoff. The anode current is plotted (black curve) Vs time with the cathode AC voltage (blue curve) varying sinusoidally. As the learner can plainly see, under most conditions the electrons which are allowed to pass through the control grid do so in bunches. This bunching behavior is similar to what is done in a klystron or magnetron. The program allows parameter contol via 4 sliders which are described below:

1. DC voltage level applied to the control grid.
2. AC voltage amplitude which is superposed on the DC voltage level.
3. Grid opacity which is the ratio of the grid elements width to the space between them
4. Number of grid elements.

For more information see Vacuum Tubes