helo topic of vacume tube

1. VACCUM TUBE

2. INTRODUCTION
• A vacuum tube is a device that controls electric current
flow in a high vacuum between electrodes to which an
electric potential difference has been applied.
• It was developed by English physicist John Ambrose
Fleming for the first time in 1904.
• The word Vacuum comes from the Latin roots. It means the
Empty or the Void

3. CURRENT USES OF VACCUM TUBE
In the 21st Century, vacuum tubes are rarely used in common electronic
equipment. Many devices today rely on the transistor over the vacuum tube.
Some devices that still use the vacuum tube however, include:
•Systems which need high frequency operation, high-power output or very high
amplification, such as television transmission, X-ray machines, radar,
and Microwave oven.
•People who enjoy listening to music on high-quality home stereo systems
sometimes buy amplifiers which use vacuum tubes
•Musicians who play electric musical instruments such as Electric
guitar sometimes use vacuum tube amplifiers.
•Vacuum fluorescent displays, which are thin vacuum tube displays that display
simple information such as numbers, are still fairly common in audio / video
equipment and household appliances, although they are being replaced by LED
displays.
•Several niche applications, such as Photomultipliers tubes.

4. WORKING OF VACCUM TUBE
All tubes follow the same basic principles. Inside a tube’s glass enclosure, you
have 1 and in vacuum 2 at least two electrodes (but often more, depending on
what type of tube we’re talking about). Each electrode has a specific job: either
releasing electrons, attracting electrons, or slowing down or speeding up the flow
of electrons. We’ll talk about these jobs later. For now, the main thing that tubes
are intended for is to direct electrical current from A to B in some way that is useful
to the circuit.
The electrodes are able to perform their jobs because all of the tube’s electrodes
are enclosed in a vacuum. Hence the “vacuum” part of vacuum tubes: during the
tube’s manufacture, the air is removed from the inside of the glass envelope. The
evidence of the tube’s vacuum is the silver metallic coating on the inside, which is
called the getter. Getter helps maintain the vacuum by removing residual gases
that are released by the materials inside the tube.
In a vacuum, electricity can travel just as easily as it does through a wire. If the
tube loses its vacuum, the electrons no longer have a clear path from electrode to
electrode, and the tube stops working. The getter is an indication of a healthy
vacuum. As long as the getter is shiny, the vacuum is good. If the getter turns
white, air has leaked into the envelope and compromised the vacuum.

5. TYPES OF VACUUM TUBE
There are following types of vacuum tube;
• Diode
• Triode
• Tetrode
• Pentode

6. DIODE
A diode is a two-terminal
electronic component that
conducts current primarily
in one direction. It has low
resistance in one direction
and high resistance in the
other.

7. TRIODE
A triode is an electronic
amplifying vacuum tube
consisting of three electrodes
inside an evacuated glass
envelope: a heated filament or
cathode, a grid, and a plate.

8. TETRODE
A tetrode is a vacuum tube
having four active electrodes.
The four electrodes in order from
the center are: a thermionic
cathode, first and second grids,
and a plate. There are several
varieties of tetrodes, the most
common being the screen-grid
tube and the beam tetrode.

9. PENTODE
A pentode is an electronic device
having five electrodes. The term
most commonly applies to a
three-grid amplifying vacuum
tube or thermionic valve that was
invented by Gilles Holst and
Bernhard D.H. Telligent in 1926.

10. THANK YOU