This document discusses 8 major types of diodes: Zener diode, varactor diode, light-emitting diode (LED), photodiode, laser diode, Schottky diode, PIN diode, and tunnel diode. For each diode type, the document provides a definition, symbol, and brief explanation of its operating principle and applications. The LED, photodiode, Zener diode, and laser diode sections provide more detailed explanations of how they work and example applications.

1. Assalamu Alikum!
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2. TYPES OF DIODE
presentation topics

3. Types of Diodes
There are following major types of diodes.
 The Zener Diode
 The Varactor Diode
 The Light-Emitting Diode
 The Photodiode
 The Laser Diode
 The Schottky Diode
 The PIN Diode
 The Tunnel Diode

4. LED
Light Emitting Diode

5. Light-Emitting Diode (LED)
 An LED emits light when forward-
biased.
 LEDs are available for either infrared
or visible light.
 High-intensity LEDs are used in large-
screen displays , traffic lights,
automotive lighting, and home lighting
etc.
Symbol:

6. Explanation:
 When the device is forward-biased, electrons
cross the pn junction from the n-type material
and recombine with holes in the p-type
material.
 The difference in energy between the
electrons and the holes corresponds to the
energy of visible light.
 When recombination takes place, the
recombining electrons release energy in the
form of photons
 The light output (both intensity and color) is
also dependent on temperature. Light
intensity goes down with higher temperature

7. The photo Diode

8. The Photo Diode:
 The photodiode is a device that
operates in reverse bias.
 The photodiode exhibits an increase in
reverse current with light intensity.
 A diode in which the reverse current
varies directly with the amount of light.
Symbol

9. Explanation:
 The photodiode has a small
transparent window that allows light to
strike the pn junction.
 when its pn junction is exposed to
light, the reverse current increases
with the light intensity. When there is
no incident light the reverse current,
is almost negligible and is called the
dark current.
 Some typical photodiodes are shown
in Figure

10. Photo diode

11. The Zener diode

12. The Zener Diode:
 A diode designed for limiting the
voltage across its terminals in reverse
bias.
 A zener diode maintains a nearly
constant voltage across its terminals
over a specified range of zener
currents.
 The zener diode operates in reverse
breakdown.

13. Explanation:
 A Zener diode is a silicon pn junction
device that is designed for operation in
the reverse-breakdown region. The
breakdown voltage of a zener diode is
set by carefully controlling the doping
level during manufacture. when a
diode reaches reverse breakdown, its
voltage remains almost constant even
though the current changes drastically,
and this is the key to zener diode
operation.

14. Continue…
 This volt-ampere characteristic is
shown again in Figure with the normal
operating region for zener diodes
shown as a shaded area.

15. The Varactor Diode

16. The Varactor Diode:
 A variable capacitance diode.
 The capacitance of a varactor varies
inversely with reverse-bias voltage
 The current regulator diode keeps its
forward current at a constant specified
value.
Symbol:

17. Explanation:
 A varactor is a diode that always
operates in reverse bias and is doped
to maximize the inherent capacitance
of the depletion region. The depletion
region acts as a capacitor dielectric
because of its nonconductive
characteristic. The p and n regions are
conductive and act as the capacitor
plates, as shown in figure:

18. The laser diode

19. The Laser Diode:
 The term Laser stands for Light
Amplification by Stimulated Emission
of Radiation.
 Laser light is Monochromatic, which
means that it consists of a single color
and not a mixture of colors.
 Laser light is also called Coherent
light, which means a single
wavelength
Symbol:

20. Aplications: Laser diodes and are used in the
pick-up system of compact disk (CD)
players.
 Laser diodes are also used in laser
printers.
 Laser diodes are also used in fiber-
optic systems.
 Laser diodes are used for the
treatment of cancer.
 There are wide uses of laser in

21. The schottky diode

22. The Schottky Diode
 Schottky diodes are high-current diodes
used primarily in high-frequency and
fast-switching applications.
 They are also known as hot-carrier
diodes
 A Schottky diode is formed by joining a
doped semiconductor region (usually n-
type) with a metal such as gold, silver, or
platinum.
Symbol:

23. The PIN Diode

24. The PIN Diode:
 The pin diode consists of heavily doped
p and n regions separated by an intrinsic
region.
 When reverse-biased, the pin diode acts
like a nearly constant capacitance.
 When forward-biased, it acts like a
current-controlled variable resistance.
 The low forward resistance of the
intrinsic region decreases with increasing
current.
 Symbol:

25. The Tunnel Diode

26. The Tunnel Diode:
 The tunnel diode exhibits a special
characteristic known as negative
resistance.
 This feature makes it useful in oscillator
and microwave amplifier applications.
 Tunnel diodes are constructed with
germanium or gallium arsenide by
doping the p and n regions much more
heavily than in a conventional rectifier
diode. This heavy doping results in an
extremely narrow depletion region

27. Allah Hafiz