Audio and Video Talk > Valves / Vacuum Tubes

The function of the electron tube (DISCUSSION)

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ghostinthemachine:
The TRIODE Electron Tube Operating As An Amplifier[/b]

To understand the most basic principle of electron tube operation you have to understand how a vacuum tube diode works.

Electrons are "boiled" off the heated (hot) CATHODE - In some cases the CATHODE are directly heated and in other the CATHODE is indirectly heated. The "free" electrons can now travel quite easily through the vacuum inside the tube. If no voltage supply is connected to the tube the electrons will go nowhere.

Letís connect the diode in a basic circuit and see what happens. The heated cathode shall be connected to the ground plane of our experimental circuit. The negative pole of the high tension (HT) direct current supply shall be connected to the ground plane as well. Now an ampere meter can be connected, in series with the positive pole of the HT supply to the ANODE of the tube. The ampere meter will indicate that current is flowing.

So, in forward current operation using the diode tube, the ANODE is positively charged so that it electrostatically attracts the emitted electrons (that is boiled off by the heat). However, electrons are not easily released from the unheated ANODE when the voltage polarity is reversed. 

Now we have established that there can only be electron from the negatively charged, heated CATHODE to the positively charged ANODE.

So how does a triode work? To be continued...

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Remeber, this discussion is open to questions and suggestions, so fire away.

ghostinthemachine:
So what happens next? Take a vacuum tube diode and place a fine metal grid between the ANODE (plate) and CATHODE. Now you have a triode.

When the grid's potential equals that of the cathode (NEGATIVELY CHARGED) no electrons can pass through to the plate or CATHODE. So we will have no electron flow.

But if we make the grid more positive than the CATHODE electrons will rush towards and then past the GRID. We now have some control over the flow of these billions of tiny electrons.                   

ghostinthemachine:

ghostinthemachine:
Above is a basic diagram for a triode amplifier.

Viagara:
Sounds essentially like an electric globe :D

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