The document discusses basic electronics, focusing on LEDs and varactor diodes. LEDs are opto-electronic devices that convert electrical energy into light and offer advantages such as high efficiency and long life but are limited in color variety and more expensive than traditional lighting. Varactor diodes are nonlinear devices used for variable capacitance in microwave circuits, with applications in voltage tuning and FM wave generation.

1. SEMINAR ON BASIC
ELECTRONICS
TOPIC-LED & VARACTOR DIODES
AVNEET SINGH LAL
EC-3

2. LED

3. ABOUT LED
 LED is an opto-electronic device which emits a narrow
bandwidth of visible or invisible light when its internal diode
junction is stimulated by a forward electric current or
voltage.
 LEDs convert electrical energy into light energy.
 The material used for LEDs are the direct Band Gap
Semiconductors which are made from group 3rd and group 5th
elements. For eg.- GaAs

4. OPERATION OF LED
 The operation of LED is based on the phenomenon
of electro luminance.
 The recombination of charge carriers takes place in
a forward p-n junction as the electrons cross from
the n-region and recombine with holes existing in
p-region.

5. ADVANTAGES OF LED
 LEDs are small in size and can be used to form
numeric and alpha numeric display in high density
matrix.
 LEDs are rugged.
 They need moderate power.
 High Lighting Efficiency
 Long Life
 High Reliability & Safety
 Environment Friendly
 Excellent Colour Rendering
 No warm up period

6. DISADVANTAGES
 A very limited variety and selection for your home
compared to other types of lighting.
 Hard to find in smaller towns where consumers may
have a smaller interest in this lighting alternative.
 Significantly more expensive than regular lighting
and not budget conscious.
 Although they are available in many colours, the
quality of the colours is not quite as good as with
regular lighting.

7. APPLICATIONS
 Medical Instrumentation
 Bar Code Readers
 Fibre Optic Communication
 Digital Cameras
 Laptops
 Traffic Signals
 Rail
 Tower Lights

8. VARACTOR DIODE

9. ABOUT VARACTOR DIODES
 A microwave solid-state device.
 Also known as a parametric diode, tuning diode or
varicap diodes
 A nonlinear device
 Provides a voltage-dependent variable capacitance
SYMBOL

10. OPERATION
 It has a p-n junction of semiconducting
material and is always reverse biased.
 The depletion zone width depends on the
applied voltage and this makes the
capacitance vary with the applied
voltage.

11. CHARACTERISTICS
 Low noise
 Low cost
 High reliability
 Light weight
 Small size
 Increase in reverse bias
of varactor diode increases
the capacitance as shown
in the figure.

12. APPLICATIONS
 Variable reactor in microwave circuits.
 It can be used for voltage tuning of
LC resonant circuit.
 It is used for generation of FM
Waves.

13. CONCLUSIONS
 Varactor diodes in reverse bias operates as
variable capacitor as reverse voltage varies, where:
 Depletion region : Dielectric (Insulator)
 P - N Regions : Plates of capacitor
 Width of Depletion region : Distance of separation

14. THE END
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