Zener Diode-Basic Electronics and Diodes-Lecture Slides, Slides for Basic Electronics. Aliah University
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sweeto13 July 2012

Zener Diode-Basic Electronics and Diodes-Lecture Slides, Slides for Basic Electronics. Aliah University

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Jagmeet Chatterji delivered this lecture at Aliah University for Basic Electronics course. Its main points are: Zener, Diode, Junction, Device, Operate, Reverse, Breakdown, Region, Characteristic, Curve
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Basic Electronic Engineering

Basic Electronic Engineering

Lecture 6

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Zener Diode

• Zener diode is a p-n junction device that is designed to operate in the reverse breakdown region

• Symbol for Zener diode

• Voltage in the reverse region remains almost constant while the current changes drastically

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Zener Diode

Zener Diode characteristic curve

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Zener Diode

Breakdown Characteristics • Reverse current( zener current) remains extremely small as the

reverse voltage is increased

• Breakdown begins when reverse current reaches IZK

• The internal resistance ZZ starts

to decrease with the increase in

current

• VZ almost remains constant with

the increase in reverse current

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Zener Diode

Zener Equivalent Circuits

Ideal Model for Zener Diode

• There is a constant voltage drop across the diode in reverse direction equal to the zener voltage

• This constant voltage drop is

modelled by a voltage source

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Zener Diode

Zener Equivalent Circuits

Practical Model for Zener Diode

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Zener Diode

• Find the diode impedance over the linear region

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Zener Diode

• Temperature coefficient specifies the change in zener voltage per degree change in temperature

• Zener diodes are specified to operate at maximum power called maximum dc power dissipation

• Power derating is the decrease in power dissipation with the increase in temperature

Z ZV V TC T    

(max)D Z ZP V I

( ) (max) ( / )D derated DP P mW C T   

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Voltage Regulation

• Zener diode is widely used as a voltage regulator that maintains a constant output voltage for change in source voltage and change in load current

Variable Input Voltage

• The zener current increase and

decrease proportionally to the

input voltage

• The variation in voltage is limited by

IZK and IZM

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Voltage Regulation

Variable Load • When the output terminals of the zener diode are open the

resistance at the output is infinity (no load condition)

• When RL is connected to the output terminal part of current flows through RL

• As RL is decreased IL increases

IZ decreases

• The zener diode continuous to

regulate until IZ < IZK

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Voltage Regulation

• Line Regulation

Line regulation specifies the change in output voltage for a given change in input voltage

• Load Regulation

Change in output voltage over a range or load currents i.e. from minimum load current to maximum load current

Line Regulation 100out in

V V

      

Load Regulation 100NL FL FL

V V V

      

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Voltage Regulation

• Determine the maximum and minimum input voltages that can be regulated by the zener diode

VZ=5.1V for IZ= 49mA, IZK=1mA and ZZ = 7 ohms.

The maximum power dissipation value is 1W

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Voltage Regulation

• Determine VOUT at IZK and IZM • Calculate the value of R that should be used

• Determine the minimum value of RL that can be used

VZ=15V for IZ=17mA, IZK=0.25mA and ZZ=14 ohm

The maximum power dissipation value is 1W

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