How Vacuum Tubes Work

this is a dial the typical two chronic to let's get inside in fundamental operation it presents an ordinary single pole switch a switch that can connect for instance this battery and it's motor lo one power lead comes to the anode the other lead goes to the cathode when this switch is open the contacts are insulated from each other by a vacuum or by some inert gas inserted into an evacuated tube under low pressure to close this switch electronically all we need do is heat the cathode and give the anode a positive potential then here's what happens as electrons are emitted from the surface of the heated cathode being negatively charged they fly a tremendous speed to the a No in this way a current-carrying path is formed which closes our electronic switch and permits our motor to operate you'll notice by the way that the direction of electron flow is contrary to the Orthodox concept of current flow from plus to minus in the first place we can rectify current with it converting AC to DC we can do this merely by connecting an electronic tube in series with an AC circuit as you study this circuit diagram note that only each positive half wave of AC voltage will now produce a current when the anode is negative the electrons are repelled and no current flow in other words because only the cathode can emit electrons we have here what amounts to a one-way street we can visualize the result of the tubes rectifying action with the aid of these two oscilloscope the one on the Left shows alternating current coming in the one on the right shows pulsating direct current going out the applications of this basic rectifying principle are many and important the second basic thing we can do with it is amplify here's how between the cathode and the anode of the two elements to which we diagram the while ago we now place a grid to this grid we connect an input of some weak voltage which we wish to amplify perhaps out of a faint radio signal from halfway around the world now let's see what happens every time a negative potential is impressed on the grid even though it'd be very my new it has a large effect in reducing the number of the negatively charged electrons which would otherwise keep flying from cathode to anode conversely when the grid is positive an equally large effect is exerted in increasing the flow of electrons from cathode we know the important thing to note here is this a small amount of power applied to the grid is amplified into a large amount of power in the anode or works circuit this amplifying property of the three element electronic tube is put to work in innumerable way

Channel: Rob Robinette

Views: 588,422

Keywords: vacuum tubes, electronic tubes, electronic valves, tube amplification, valve amplification, guitar tube amps

Id: nA_tgIygvNo

Length: 3min 50sec (230 seconds)

Published: Mon Aug 24 2015