Diode Valve and Triode Valve

What is Diode Valve ?

Answer: - Designed by J.A. Fleming in 1904, consisting of two electrodes placed inside an evacuated glass tube. One electrode is called Cathode having filament of Tungsten and the other electrode is Anode made up a copper plates. Filament is coated with Barium Oxide. When it is heated, negatively charged cathode emits electrons. These electrons go to the Anode plate which is under positive potential.

When heated the electrons emitted from cathode are collected in the evacuated space within tube around Cathode in the space forming cloud of electrons called space charge. Under positive potential of Anode space charge is collected in one plate.

Diode Valves act as a Rectifier converting A.C. voltage to D.C. voltage.

Diode and Triode Valve

What is Triode Valve ?

Answer: - Designed by Lee De Forest in 1907, Triode valve is having an additional electrode modifying a diode.

Besides Anode-Cathode pair of Diode it has another electrode called Grid that controls filament current. This is called control grid.

Triode valve can be used as amplifier, oscillator, transmitter and detector of Radio wave.

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