Name: Ahmed KhaledID: 14105269

Vacuum Tubes

invented in 1904 by John Ambrose Fleming

 vacuum tubes were a basic component for electronics throughout the 20th century

 diffusion of radio, television, radar, sound recording and digital computers.

How Vacuum tubes works :

Vacuum tubes mostly rely on  a cathode heated by the filament  is called a thermionic tube or thermionic valve.

electron emission through the photoelectric effect.

Diodes : invented by John Ambrose

Fleming

could be used as a rectifier of AC and as a radio wave detector

Triodes  :

The only one who succeeded was inventor Lee de Forest in 1907.

By placing an additional electrode between cathode and anode.

 the grid was changing the current flowing from the cathode to the Anode

Used in big radio stations, especially for power levels above 10,000 watts and for frequencies above 50 MHz. High-power TV stations and large FM stations are almost exclusively powered by tubes. The reason is cost and efficiency

Vacuum tube devices :

Cathode ray tubes •Vacuum fluorescent display

Vacuum tubes using field electron emitters

design uses a cold cathode in the form of a large-area field electron source( field emitter array).

include much and the ability to provide high power output at low power consumption

 we may find application in : microwave devices including mobile

phones for :Bluetooth Wi-Fi in radar and for satellite communication

Gas-Filled Tube :

 and operate by ionizing the gas with an applied voltage

Ionizing is dependent on the pressure of the fill gas and geometry of the tube

•Nobel Gases :

Helium :is used in helium–neon lasers Neon : Used in fluorescent tubes with high

power and short length, e.g. industrial lighting tubes

References :

http://www.vacuumtubes.net/How_Vacuum_Tubes_Work.htm

http://www.answers.com/Q/What_is_the_uses_of_triode_transistor