ec2155 devices lab manual

7/28/2019 EC2155 Devices lab manual

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CHARACTERISTICS OF PN JUNCTION DIODE AND ZENER DIODE

(a) CHARACTERISTICS OF PN JUNCTION DIODE

AIM:

To study the characteristics of PN junction diode and to plot the volt amperecharacteristics.

APPARATUS REQUIRED:

Sl. No. Equipments & Components Range/ Specification Quantity

1 RPS (0-30) V 1

2 Diode 1N4001 1

3 Ammeter (0-30) mA, (0-500) A 1 each

4 Voltmeter (0-1) V, (0-15) V 1 each

5 Resistor 1 K 16 Bread Board 1

7 Connecting wires As required

THEORY:

A Semiconductor PN junction diode is an electronic device that is fabricated bysandwiching a P type material with an N type material. The diode is basically referred to asrectifier diode, as it is used in converting an AC signal to DC signal. The material useddetermines the cut-in voltage of diode, for Germanium it is 0.3 V and for silicon it is 0.7 V. The

diode is a resistive element, which conducts only when the voltage is above rated voltage it isreferred to as barrier voltage. The diode conducts in both forward and reverse mode. In theforward mode the resistance offered by the diode is small. Diode is connected in forwarddirection with P type connected to the positive node in the supply and N type connected tothe negative node of the supply, once the applied voltage exceeds the barrier voltage the diodestarts conducting which leads to saturation.

PROCEDURE:

FORWARD BIASING:

(1) Connect the circuit as per the circuit diagram 1.

(2) Vary the power supply voltage in such a way that readings should be taken in stepsof 0.05 V in the voltmeter till the power supply shows 1 V.

(3) Note down the corresponding ammeter readings.

(4) Plot the graph: VF Vs IF.


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(5) Find the dynamic resistance FFF

Vr

I

REVERSE BIASING:


(2) Vary the power supply voltage in such a way that readings should be taken in stepsof 1 V in the voltmeter till the power supply shows 15 V.


(4) Plot the graph: VR Vs IR

(5) Find the dynamic resistance RRR

Vr

I

CIRCUIT DIAGRAM:

Figure 1. Forward Biasing

Figure 2. Reverse Biasing


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MODEL GRAPH:

TABULAR COLUMN:

Forward Bias Reverse BiasVF (volts) IF (mA) VR (volts) IR (mA)


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CALCULATION:

RESULT:

Thus the V-I characteristics of a PN junction diode is studied and the graph is plotted.

From graph, Forward Resistance = ______________

Reverse Resistance = _______________

Cut-in voltage = ____________


5/23

(b) CHARACTERISTICS OF ZENER DIODE

AIM:

To study the characteristics of Zener diode and to plot the volt ampere characteristics.

APPARATUS REQUIRED:


1 RPS (0-30) V 1

2 Diode FZ 9.1 1

3 Ammeter (0-30) mA, (0-1) mA 1 each


5 Resistor 1 K 1

6 Bread Board 1


THEORY:

A semiconductor Zener Diode is an electronic device that is fabricated by sandwiching aP type material with an N type material. The diode is basically referred to as Reference /Regulator diode, as it is used to regulate DC signal. The diode works in the reverse break downregion in a different way that is based on the geometry of doping. The diode conducts in bothforward and reverse mode. The diode is primarily used in the reverse direction only. Thevoltage at which the diode breaks is known as Zener break down. It is due to the appliedvoltage reverse potential, an electric field exists near the junction, this field exist a strong fieldon the covalent bond and this breaks the band, leading to Zener breakdown.

PROCEDURE:

FORWARD BIASING:


(2) Vary the power supply voltage in such a way that readings should be taken in stepsof 0.05 V in the voltmeter till the power supply shows 1 V.


(4) Plot the graph: VF Vs IF.

(5) Find the dynamic resistance FFF

VrI

REVERSE BIASING:



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(2) Vary the power supply voltage in such a way that readings should be taken in stepsof 1 V in the voltmeter till the power supply shows 15 V.


(4) Plot the graph: VR Vs IR

(5) Find the dynamic resistance RRR

Vr

I

CIRCUIT DIAGRAM:

Figure 1. Forward Biasing

Figure 2. Reverse Biasing


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MODEL GRAPH:

TABULAR COLUMN:

Forward Bias Reverse Bias

VF (volts) IF (mA) VR (volts) IR (mA)


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CALCULATION:

RESULT:

Thus the V-I characteristics of a Zener diode is studied and the graph is plotted.

From graph, Forward Resistance = ______________

Reverse Resistance = _______________

Cut-in voltage = ____________

Breakdown voltage = _____________


9/23

CHARACTERISTICS OF BJT CE CONFIGURATION

AIM:

To plot the input and output characteristics of a Bipolar Junction Transistor in CommonEmitter Configuration.

APPARATUS REQUIRED::::


1 RPS (0-30) V 2

2 Transistor BC 107 1

3 Ammeter (0-30) mA, (0-150) A 1 each


5 Resistor 1 K 2

6 Bread Board 17 Connecting wires As required

THEORY:

The transistor is a semiconductor device having three layers called emitter, base andcollector. It consists of two diodes namely emitter base diode and collector base diodeconnected back to back. Bipolar Junction Transistor is classified into NPN and PNP transistor.The doping varies between the three layers. Always the emitter base junction is forwardbiased and collector base is reverse biased. The DC characteristics are divided into INPUTand OUTPUT characteristics.

PROCEDURE:

INPUT CHARACTERISTICS:

(1)Connect the circuit as per the circuit diagram.

(2) Set VCE = 0V, vary VBB in steps of 1V to 15V and note down the corresponding IB andVBE. Repeat the above procedure for VCE = 5V, 10V, 15V, etc.

(3) Plot the graph: VBE Vs IB for a constant VCE.

(4) Find the h- parameters.

Input Impedance, |BEie CE B

Vh V const

I

Reverse Voltage Gain, |BEre BCE

Vh I const

V


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OUTPUT CHARACTERISTICS:

(1) Connect the circuit as per the circuit diagram.

(2) Set IB= 10A, vary VCC in steps of 1V to 15V and note down the corresponding IC and

VCE. Repeat the above procedure for IB = 20 A, 30A, 40A etc.

(3) Plot the graph: VCE Vs IC for a constant IB.

(4) Find the h- parameters.

Forward Current Gain, |Cfe CEB

Ih V const

I

Output Admittance, |Coe BCE

Ih I const V

CIRCUIT DIAGRAM:

MODEL GRAPH:

Input Characteristics


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Output Characteristics

TABULAR COLUMN:


VCE = _______ volts VCE = _______ volts VCE = ______ volts

VBE (volts) IB (A) VBE (volts) IB (A) VBE (volts) IB (A)


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CALCULATIONS:

RESULT:

Thus the input and output characteristics of the given transistor are plotted and theparameters are calculated as

hie = _______ (ohms) hre = _______ (no unit)

hfe = _______ (no unit) hoe = _______ (mhos)

IB = _______ A IB = _______ A IB = _______ A

VCE (volts) IC (mA) VCE (volts) IC (mA) VCE (volts) IC (mA)


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CHARACTERISTICS OF BJT CB CONFIGURATION

AIM:

To study the input and output characteristics of a Bipolar Junction Transistor inCommon Base configuration and to calculate its hybrid parameters.

APPARATUS REQUIRED:


1 RPS (0-30) V 2

2 Transistor BC 107 1

3 Ammeter (0-10) mA 2


5 Resistor 1 K 2

6 Bread Board 17 Connecting wires As required

THEORY:

The transistor is a semiconductor device having three layers called emitter, base andcollector. It consists of two diodes namely emitter base diode and collector base diodeconnected back to back. Bipolar Junction Transistor is classified into NPN and PNP transistor.The doping varies between the three layers. Always the emitter base junction is forwardbiased and collector base is reverse biased. The DC characteristics are divided into INPUTand OUTPUT characteristics.

PROCEDURE:

(1) The connections are made as shown in the circuit diagram.

(2) The input voltage VBE is varied in small steps and the input current IE is noted bykeeping the output voltage VCB as constant. The readings are tabulated.

(3) The same procedure is repeated for different values of VCB. A set of inputcharacteristics is drawn between IE and VBE.

(4) For output characteristics, the input current IE is set to a constant value. The outputvoltage VCB is varied in small steps and output current IC is noted. The readings are tabulated.

(5) The experiment is repeated for different constant values of input current I E. A set ofoutput characteristics is drawn between VCB and IC.

(6) The h-parameters are calculated using the following formulas.

Input Impedance, |BEib CBE

Vh V const

I


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Reverse Voltage Gain, |EBrb ECB

Vh I const

V

Forward Current Gain, |Cfb CBE

Ih V const I

Output Admittance, |Cob ECB

Ih I const

V

CIRCUIT DIAGRAM:

MODEL GRAPH:

Input Characteristics


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Output Characteristics

TABULAR COLUMN:


VCB = _______ volts VCB = _______ volts VCB = ______ volts

VBE (Volts) IE (mA) VBE (Volts) IE (mA) VBE (Volts) IE (mA)


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CALCULATIONS:

RESULT:

Thus the input and output characteristics of the given transistor in common base modeare plotted and the parameters are calculated as

hib = _______ (ohms) hrb = _______ (no unit)

hfb = _______ (no unit) hob = _______ (mhos)

IE = _______ mA IE = _______ mA IE = _______ mA

VCB (volts) IC (mA) VCB (volts) IC (mA) VCB (volts) IC (mA)


17/23

CHARACTERISTICS OF UNIJUNCTION TRANSISTOR

AIM:

To plot the characteristics of a given Unijunction Transistor (UJT) and to determine its

intrinsic stand-off ratio.

APPARATUS REQUIRED:


1 RPS (0-30) V 2

2 Transistor (UJT) 2N 2646 1


4 Voltmeter (0-30) V 2

5 Resistor 1 K, 560 1 each

6 Bread Board 1


THEORY:

The Unijunction Transistor consists of a bar of lightly doped n-type silicon with a smallpiece of heavily doped p type material joined to one side. The end terminal of the bar isdesignated base1 (B1) and base2 (B2) and the p type region is termed the emitter (E). thesilicon bar is lightly doped as it has high resistance and can be represented as high resistorsshown in equivalent circuit. The p type emitter forms a PN junction with the n type siliconbar and this junction is represented by a diode in the equivalent circuit. When a voltage isapplied between two bases it divides between two resistances in the ratio of their values. Let

V1 be the voltage across resistor RB1. Now when emitter is forward biased and if the forwardbias voltage is less than V1, then the diode is actually reverse biased and the device will be incut off.

If the emitter voltage is increased above V1, the emitter current flows. The voltage atwhich the device starts conduction is called peak voltage VP. When the emitter voltage isincreased beyond VP, the charge carriers are injected into the n region and the resistance startsdecreasing since the resistance depends on doping. Now the device enters negative resistanceregion. As voltage increased, the current decreases. If IE increases, the resistance decreases andwhen the current reaches a certain limit the resistance RS is saturated. The voltage falls to a lowvalue called valley voltage VV. After this valley point if forward voltage is increased further

the emitter current increases rapidly with slight increase in emitter voltage similar to forwardbiased diode.

PROCEDURE:


(2) Set base voltage VB1B2 = 5V, vary VEE in steps of 1V up to 15V and note down thecorresponding IE and VEB1.


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(3) Repeat the above procedure for VB1B2 = 10V, 15V, etc.

(4) Plot the graph: IE Vs VEB1 for a constant VB2B1.

(5) Find the intrinsic stand-off ratio

1 2

P D

B B

V V

V

where VD = 0.7 V

CIRCUIT DIAGRAM:

MODEL GRAPH:


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TABULAR COLUMN:

CALCULATION:

RESULT:

The characteristics of a given Unijunction transistor is studied and the graph is been

plotted. The intrinsic stand-off ratio is determined as

= (no unit)

VB1B2 = _______ volts VB1B2 = _______ volts VB1B2 = _______ volts

VEB1 (volts) IE (mA) VEB1 (volts) IE (mA) VEB1 (volts) IE (mA)


20/23

CHARACTERISTICS OF JUNCTION FIELD EFFECT TRANSISTOR

AIM:

To plot the drain and transfer characteristics of a given JFET and to calculate itsparameters.

APPARATUS REQUIRED:


1 RPS (0-30) V 2

2 Transistor (JFET) BFW 10 1



5 Resistor 1 K 2

6 Bread Board 1


THEORY:

The Field Effect Transistor is a semiconductor device which depends for its operation onthe control of current by an electric field. In a conventional transistor the operation depends onboth types of carries, but in FET it primarily depends on majority carriers, hence FET is calledunipolar device. Here FET has a channel type construction fabrication with the channelpaving the way for the current to move through it. There is a gate provision to control the flowwith the help of gate current and voltage. There are two types of FET, N-channel and P-channel.

PROCEDURE:

DRAIN CHARACTERISTICS:


(2) Set gate voltage VGS = 0V, vary VDS in steps of 1V and note down the correspondingID and VDS.

(3) Repeat the above procedure for VGS = -5V, -10V, -15V, etc.

(4) Plot the graph: VDS Vs ID for a constant VGS.

(5) Calculate the drain resistance, |DSD GSD

Vr V const

I

TRANSFER CHARACTERISTICS:


(2) Set drain voltage VDS = 5V, vary gate to source voltage VGS in steps of 0.5 V and notedown the corresponding ID and VGS.


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(3) Repeat the above procedure for VDS = 10V, 15V, etc.

(4) Plot the graph: VGS Vs ID for a constant VDS.

(5) Find the Transconductance, |Dm DSGS

Ig V const

V

The amplification factor is calculated from the formula, .m Dg r

CIRCUIT DIAGRAM:

TABULAR COLUMN:

DRAIN CHARACTERISTICS:

VGS = _______ volts VGS = _______ volts VGS = _______ volts

VDS (volts) ID (mA) VDS (volts) ID (mA) VDS (volts) ID (mA)


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TRANSFER CHARACTERISTICS:

MODEL GRAPH:

Drain Characteristics Transfer Characteristics

VDS = _______ volts VDS = _______ volts VDS = _______ volts

VGS (volts) ID (mA) VGS (volts) ID (mA) VGS (volts) ID (mA)


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CALCULATIONS:

RESULT:

The drain and transfer characteristics of the Junction Field Effect Transistor are plottedand the parameters are calculated.

(i) Drain Resistance =(ii) Transconductance =(iii) Amplification factor =

ec2155 devices lab manual

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