Lecture 3

Introduction to Electronics Introduction to Electronics

Rabie A. Ramadanrabieramadan@gmail.com

http://www.rabieramadan.org/classes/2014/electronics/

2

Zener Diode

Lecture 4, Slide 3

Zener Diode

• The linear approximation to the I-V characteristic of a zener diode in the reverse bias and breakdown regions is as follows.

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Zener Diode

• The slope of the line at Q is 1/rZ

• rZ is called the incremental resistance of the zener diode

• This is exaggerated for clarity in the figure. In practice rZ is small (a few ohms) and the breakdown voltage is approximately constant irrespective of the reverse current.

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Zener Diode

• Zener breakdown occurs when the electric field in the depletion layer increases to the point where it can break covalent bonds and generate electron-hole pairs.

• Electrons generated in this way are swept by the electric field into the n side.

• Holes generated in this way are swept by the electric field into the p side.

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Zener Diode

• With this notation, in the zener region:• Vz = Vzo + rzIz

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Relation between the temperature and Zener Voltage

• Tc: Temperature coefficient (given)• T1 : applied temperature • T0 : operational temperature • Vz : applied voltage • New VZ = VZ +

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Group Activity

• Determine the nominal voltage for the Zener diode of Table 1.4 at a temperature of 100°C.

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Solution

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LIGHT-EMITTING DIODES

LED are semiconductor p-n junctions that under forward bias conditions can emit radiation by electroluminescence in the UV, visible or infrared regions of the electromagnetic spectrum. The qaunta of light energy released is approximately proportional to the band gap of the semiconductor.

Semiconductors

bring quality

to light!

What is LED?

Applications of LEDs

Your fancy telephone, i-pod, palm pilot and digital camera

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Getting to know LEDAdvantages of Light Emitting Diodes (LEDs)Longevity: The light emitting element in a diode is a small conductor chip rather than a filament which greatly extends the diode’s life in comparison to an incandescent bulb (10 000 hours life time compared to ~1000 hours for incandescence light bulb)Efficiency: Diodes emit almost no heat and run at very low amperes.Greater Light Intensity: Since each diode emits its own lightCost:Not too badRobustness:Solid state component, not as fragile as incandescence light bulb

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LOAD-LINE ANALYSIS• Given the following :

–Forward Biased Diode

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LOAD-LINE ANALYSIS

• The intersections of the load line on the characteristics can easily be determined if one simply employs the fact that anywhere on the horizontal axis ID = 0 A and anywhere on the vertical axis VD = 0 V.

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LOAD-LINE ANALYSIS

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LOAD-LINE ANALYSIS

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LOAD-LINE ANALYSISThe point of operation is usually called the quiescent point (abbreviated “Q-pt.”)

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Group Work

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Solution

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Solution (Cont.)

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Group Activity

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Solution

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