VACCUM TUBE and its work of computer ///

helo topic of vacume tube

1. VACCUM TUBE

2. INTRODUCTION
•Avacuumtubeisadevicethatcontrolselectriccurrent
flowinahighvacuumbetweenelectrodestowhichan
electricpotentialdifferencehasbeenapplied.
•ItwasdevelopedbyEnglishphysicistJohnAmbrose
Flemingforthefirsttimein1904.
•ThewordVacuumcomesfromtheLatinroots.Itmeansthe
EmptyortheVoid

3. CURRENT USES OF VACCUM TUBE
Inthe21
st
Century,vacuumtubesarerarelyusedincommonelectronic
equipment.Manydevicestodayrelyonthetransistoroverthevacuumtube.
Somedevicesthatstillusethevacuumtubehowever,include:
•Systemswhichneedhighfrequencyoperation,high-poweroutputorveryhigh
amplification,suchastelevisiontransmission,X-raymachines,radar,
andMicrowaveoven.
•Peoplewhoenjoylisteningtomusiconhigh-qualityhomestereosystems
sometimesbuyamplifierswhichusevacuumtubes
•MusicianswhoplayelectricmusicalinstrumentssuchasElectric
guitarsometimesusevacuumtubeamplifiers.
•Vacuumfluorescentdisplays,whicharethinvacuumtubedisplaysthatdisplay
simpleinformationsuchasnumbers,arestillfairlycommoninaudio/video
equipmentandhouseholdappliances,althoughtheyarebeingreplacedbyLED
displays.
•Severalnicheapplications,suchasPhotomultiplierstubes.

4. WORKING OF VACCUM TUBE
Alltubesfollowthesamebasicprinciples.Insideatube’sglassenclosure,you
have1andinvacuum2atleasttwoelectrodes(butoftenmore,dependingon
whattypeoftubewe’retalkingabout).Eachelectrodehasaspecificjob:either
releasingelectrons,attractingelectrons,orslowingdownorspeedinguptheflow
ofelectrons.We’lltalkaboutthesejobslater.Fornow,themainthingthattubes
areintendedforistodirectelectricalcurrentfromAtoBinsomewaythatisuseful
tothecircuit.
Theelectrodesareabletoperformtheirjobsbecauseallofthetube’selectrodes
areenclosedinavacuum.Hencethe“vacuum”partofvacuumtubes:duringthe
tube’smanufacture,theairisremovedfromtheinsideoftheglassenvelope.The
evidenceofthetube’svacuumisthesilvermetalliccoatingontheinside,whichis
calledthegetter.Getterhelpsmaintainthevacuumbyremovingresidualgases
thatarereleasedbythematerialsinsidethetube.
Inavacuum,electricitycantraveljustaseasilyasitdoesthroughawire.Ifthe
tubelosesitsvacuum,theelectronsnolongerhaveaclearpathfromelectrodeto
electrode,andthetubestopsworking.Thegetterisanindicationofahealthy
vacuum.Aslongasthegetterisshiny,thevacuumisgood.Ifthegetterturns
white,airhasleakedintotheenvelopeandcompromisedthevacuum.

5. TYPES OF VACUUM TUBE
Therearefollowingtypesofvacuumtube;
•Diode
•Triode
•Tetrode
•Pentode

6. DIODE
Adiodeisatwo-terminal
electroniccomponentthat
conductscurrentprimarily
inonedirection.Ithaslow
resistanceinonedirection
andhighresistanceinthe
other.

7. TRIODE
Atriodeisanelectronic
amplifyingvacuum tube
consistingofthreeelectrodes
insideanevacuatedglass
envelope:aheatedfilamentor
cathode,agrid,andaplate.

8. TETRODE
Atetrodeisavacuumtube
havingfouractiveelectrodes.
Thefourelectrodesinorderfrom
thecenterare:athermionic
cathode,firstandsecondgrids,
andaplate.Thereareseveral
varietiesoftetrodes,themost
commonbeingthescreen-grid
tubeandthebeamtetrode.

9. PENTODE
Apentodeisanelectronicdevice
havingfiveelectrodes.Theterm
mostcommonlyappliestoa
three-gridamplifyingvacuum
tubeorthermionicvalvethatwas
inventedbyGillesHolstand
BernhardD.H.Telligentin1926.

10. THANK YOU