zener diode experminet manual

8/13/2019 zener diode experminet manual

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ZENER DIODE CHARACTERISTICSObjective:

1. To plot Volt-Ampere characteristics of Zener diode.

2. To find Zener break down voltage in reverse biased condition.3. To calculate static and d namic resistances of the Zener diode in both

forward and reverse biased conditions !before" after break downvoltages#.

Components:

Equipment:

Name Range

$readboard%egulated &' power suppl

Ammeter

Voltmeter

'onnecting (ires

-)-3)V

)-2)mA

)-2)V

Speci ications:

$reakdown Voltage * +.1V

,ower dissipation * ). +(

a/. 0orward 'urrent * 1A

T!eo"#: An ideal ,- unction diode does not conduct in reverse biasedcondition. A $ene" %io%e conducts e/cellentl even in reverse

Name &t#Zener &iode

%esistor1

1

1


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biased condition. These diodes operate at a precise value ofvoltage called break down voltage.

A $ene" %io%e when forward biased behaves like an ordinar ,-

4unction diode.A $ene" %io%e when reverse biased can either undergoava'anc!e b"ea( %o)n or $ene" b"ea( %o)n .

Ava'anc!e b"ea( %o)n 5-6f both p-side and n-side of the diodeare lightl doped" depletion region at the 4unction widens.Application of a ver large electric field at the 4unction marupture covalent bonding between electrons. 7uch rupture leadsto the generation of a large number of charge carriers resultingin ava'anc!e mu'tip'ication .

Zene" b"ea( %o)n 5- 6f both p-side and n-side of the diode areheavil doped" depletion region at the 4unction reduces.Application of even a small voltage at the 4unction rupturescovalent bonding and generates large number of charge carriers.7uch sudden increase in the number of charge carriers results in$ene" mec!anism .

Ci"cuit Diag"am:

*ig +,- . *o")a"% /ias Con%ition:

% ) 8 2)mA

1k

)-2)V

Vin 15V


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*ig +0- . Reve"se /ias Con%ition:

% ) 8 2)mA

1k

Vin )-2)V15V

1"oce%u"e:

*o")a"% biase% con%ition:

1. 'onnect the circuit as shown in fig !1#.

1. Var V9f graduall and note down the corresponding readings of 69 f .2. 7tep 7i9e is not fi/ed because of non linear curve and var the :-a/is

variable !i.e. if output variation is more" decrease input step si9e andvice versa#.

2. Tabulate different forward currents obtained for different forwardvoltages.

Reve"se biase% con%ition:

1. 'onnect the circuit as shown in fig !2#.

2. Var V9r graduall and note down the corresponding readings of 69r .3. 7tep 7i9e is not fi/ed because of non linear curve and var the :-a/is

variable !i.e. if output variation is more" decrease input step si9e andvice versa#.

;. Tabulate different reverse currents obtained for different reversevoltages.


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Obse"vations:Zene" %io%e in *o")a"% Zene" %io%e in "eve"sebiase% con%ition: biase% con%ition:

2"ap! +Inst"uctions-:1. Take a graph sheet and divide it into ; e


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VZf !volts#

6Zr !mA#

3. ark the readings tabulated for 9ener diode forward biased conditionin first >uadrant and 9ener diode reverse biased condition in third>uadrant.

Ca'cu'ations "om 2"ap!:

7tatic forward %esistance % dc * Vf?6f& namic forward %esistance r ac * Vf? 6f7tatic %everse %esistance % dc * Vr?6r

& namic %everse %esistance r ac * Vr? 6r

1"ecautions:1. (hile doing the e/periment do not e/ceed the ratings of the diode.

This ma lead to damage the diode.2. 'onnect voltmeter and Ammeter in correct polarities as shown in

the circuit diagram.3. &o not switch ON the power suppl unless ou have checked the

circuit connections as per the circuit diagram.In e"ence:

1. 6n the forward biased mode the 9ener diode operates as a p-n diode.

2. 6n the reverse biased mode 9ener diode has large breakdown voltageand though the current increases the voltage remains constant. Thusit acts as a voltage regulator.

Resu't:1. The 9ener diode characteristics have been studied.2. The 9ener resistance at the breakdown voltage was found to

be * @@@

Reasoning &uestions1. (hat is a 9ener diode Bow it differs from an ordinar diode

2. C/plain the concept of 9ener breakdown

3. (hat is avalanche breakdown


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;. (hat t pe of biasing must be used when a 9ener diode is used as aregulator

+. 'urrent in a 1( 8 1)V 9ener diode must be limited to a ma/imum ofwhat value

D. (hat are the advantages of 9ener diode. 7tate reason wh an ordinar diode suffers avalanche breakdown

rather than 9ener breakdown

E. 6f impurities in a 9ener diode increases what happens to the forwardvoltage

F. 'an 9ener be used as a rectifier

1). 7pecifications of the 9ener diode

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zener diode experminet manual