electronic devices and circuits lab manual (17aec07) … · scr characteristics . index s. no. date...

Sri Venkateswara College of Engineering and Technology, Chittoor (Autonomous)

Department of Electronics and Communication Engineering

ELECTRONIC DEVICES AND CIRCUITS LAB MANUAL (17AEC07)

(II B.Tech -I Semester ECE)

ROLL NO: _______________________________________

NAME: __________________________________________

CLASS: __________________________________________

ELECTRONIC DEVICES AND CIRCUITS LAB - 17AEC07

Objectives: 1. To understand the working of diode, transistors.

2. To understand the working of special purpose electronics devices.

3. To understand the working of a rectifier circuit with and without filters.

4.To understand the bandwidth calculations of an amplifier circuit.

Outcomes: At the end of the course, the student should be able to: 1. Analyze CE, CB and CS amplifiers and its bandwidth calculation.

2. Calculate various parameters from the characteristics of various electronic devices.

3. Know the importance of Filters and its calculations.

4. Calculate the bandwidth of the BJT and FET in different configurations.

Electronic Workshop Practice:

1. Identification, Specifications, Testing of R, L, C Components (Color Codes),

Potentiometers, Coils, Gang Condensers, Relays, Bread Boards.

2. Identification, Specifications and Testing of active devices, Diodes, BJTs, JFETs,

LEDs, LCDs, SCR, UJT.

3. Soldering Practice- Simple circuits using active and passive components.

4. Study and operation of Ammeters, Voltmeters, Transformers, Analog and Digital

MultiMeter, Function Generator, Regulated Power Supply and CRO.

List of Experiments

Minimum of Ten Experiments need to be conducted

1. Study of CRO Operation and its Applications.

2. P-N Junction Diode Characteristics

3. Zener Diode Characteristics

i) V-I Characteristics

ii) Zener Diode act as a Voltage Regulator

4. Rectifiers (without and with filter)

i) Half-wave Rectifier

ii) Full-wave Rectifier

5. BJT Characteristics (CE Configuration)

i) Input Characteristics

ii) Output Characteristics

6. BJT Characteristics (CB Configuration)

i) Input Characteristics

ii) Output Characteristics

7. FET Characteristics (CS Configuration)

i) Drain (Output) Characteristics

ii) Transfer Characteristics

8. SCR Characteristics.

9. UJT Characteristics.

10. LDR Characteristics.

11. LED Characteristics.

12. Transistor Biasing.

Cycle- I

1. Study of CRO Operation and its Applications.

2. P-N Junction Diode Characteristics

3. Zener Diode Characteristics

4. Half-wave Rectifier & Full-wave Rectifier Rectifiers (without and with c-filter)

5. BJT Characteristics (CE Configuration)

Cycle- II

1. BJT Characteristics (CB Configuration)

2. FET Characteristics (CS Configuration)

3. UJT Characteristics.

4. LED Characteristics.

5. SCR Characteristics

INDEX

S. No. Date

Name of the Experiment Remarks

ELECTRONIC WORKSHOP PRACTICE

1. Identification, Specifications, Testing of R, L, C Components (Color Codes), Potentiometers, Coils, Gang

Condensers, Relays, Bread Boards.

RESISTOR COLOR CODE

To read them, hold the resistor such that the tolerance band is on your right. The tolerance band is

usually gold or silver in color and is placed a little further away from the other bands.

Starting from your left note all the colors of the bands and write them down in sequence. Next, use the

table given below to see which digits they represent. The band just next to the tolerance band is the

multiplier band. So if the color of this band is Red (representing 2), the value given is 102.

CAPACITORS

CERAMIC CAPACITOR

Below is a very useful chart for calculation the right value of Ceramic / Non – Polarized Capacitors.

There are special codes and marking on capacitor, which tell about the value of capacitor.

Example:

Here is the Capacitor marking is “105”

It’s mean that = 10 + 5 Zeros = 1,000,000 pF

= 1000 nF = 1 µF

ELECTROLYTIC CAPACITOR

The Electrolytic Capacitors have polarity. Meaning they have a positive and negative pin. The pin which

is long is the positive pin and the pin which is short is the negative pin. You can also identify the polarity

using the negative strip on the capacitor label.

POTENTIOMETERS

A potentiometer is a three-terminal resistor with a sliding or rotating contact that forms an

adjustable voltage divider. If only two terminals are used, one end and the wiper, it acts as a variable

resistor or rheostat.

BREADBOARD

A breadboard is a solderless device for temporary prototype with electronics and test circuit designs.

Most electronic components in electronic circuits can be interconnected by inserting their leads or

terminals into the holes and then making connections through wires where appropriate.

BREAD BOARD LAYOUT :

SAMPLE CONNECTION

http://wiring.org.co/learning/tutorials/breadboard/

2. Identification, Specifications and Testing of active devices, Diodes, BJTs, JFETs, LEDs, LCDs, SCR,

UJT.

DIODE

TRANSISTOR

BJT – BIPOLAR JUNCTION TRANSISTOR

BC107 BOTTOM VIEW OF BJT

JFET – JUNCTION FIELD EFFECT TRANSISTOR

LED – LIGHT EMITTING DIODE

SCR – SILICON CONTROL RECTIFIER

UJT - UNI JUNCTION TRANSISTOR

SRI VENKATESWARA COLLEGE OF ENGINEERING AND TECHNOLOGY

(AUTONOMOUS)

DEPT. OF ECE

EXPERIMENT NO.: DATE:

====================================================================

STUDY OF CRO OPERATION AND ITS APPLICATIONS

AIM:

To observe front panel control knobs and to find amplitude, time period and frequency for given

waveforms.

APPARATUS:

1. CRO --------------- 1No.

2. Function generator --------------- 1No.

3. CRO Probes --------------- 1No.

THEORY:

C.R.O. (Cathode Ray Oscilloscope) is the instrument which is used to observe signal waveforms. Signals

are displayed in time domain i.e. variation in amplitude of the signal with respect to time is plotted on the

CRO screen. X-axis represents time and Y-axis represents amplitude. It is used to measure amplitude,

frequency and phase of the waveforms. It is also used to observe shape of the waveform.

It helps us to find out gain of amplifier, test oscillator circuits. We can measure amplitude and frequency

of the waveforms at the different test points in our circuit. Thus, it helps us for fault finding procedure. In

dual channel C.R.O, X-Y mode is available which is used to create Lissajous patterns.

Latest digital storage oscilloscope display voltage and frequency directly on the LCD and does not

require any calculations. It can also store waveform for further analysis.

Page 1

Time in ms

Amplitude in Volts

Time Period

Time in ms

Amplitude in Volts

Time period

Time in ms

Amplitude in Volts

Time period

MODEL GRAPHS:

Sinusoidal Signal:

Traingular Signal:

Square Signal:

Page 2

PROCEDURE:

1. Understand the significance of each and every knob on the CRO.

2. From the given function generator feed in a sinusoidal wave and adjust the time base

knob and the amplitude knob to observe the waveform as a function of time.

3. Measure the time period and amplitude (peak to peak) of the signal. Find the frequency

and verify if the same frequency is given from the function generator.

4. Repeat the above steps for square and triangular waveforms.

5. Report the readings and take the waveforms.

APPLICATIONS OF CRO:

1. Measurement of current

2. Measurement of voltage

3. Measurement of power

4. Measurement of frequency

5. Measurement of phase angle

6. To see transistor curves

7. To trace and measuring signals of RF, IF and AF in radio and TV.

8. To trace visual display of sine waves.

Page 3

CALCULATIONS:

Sinusoidal Signal:

Amplitude =

Time Period =.

Frequency =

Triangular Signal:

Amplitude =

Time Period =.

Frequency =

Square Signal:

Amplitude =

Time Period =.

Frequency =

Page 4

RESULT:

Thus the waveforms are observed and amplitude, time period and frequency are calculated.

Page 5


(AUTONOMOUS)

DEPT. OF ECE


====================================================================

PN JUNCTION DIODE CHARACTERISTICS

AIM:

To verify the V-I Characteristics of given P-N Junction diode in Forward and Reverse bias and also to

find the Cut-in Voltage, Static Resistance and Dynamic Resistance in forward bias condition.

APPARATUS REQUIRED:

4. P-N Junction diode – 1N 4007 --------------- 1No.

5. Resistor – 1KΏ --------------- 1No.

6. Bread Board --------------- 1No.

7. Voltmeter (0-1V, 0-20V) --------------- 1No.

8. Ammeter (0-50mA, 0-250µA) --------------- 1No.

9. Regulated Power Supply (0-30V) ---------------- 1No.

10. Connecting wires (required as per circuit)

FORMULAE:

1. Static Resistance (Rs) =

2. Dynamic Resistance (RD) =

THEORY:

When the voltage is applied between the two terminals of the diode (anode and cathode) two possibilities

arises depending on polarity of DC supply.

[1] Forward-Bias Condition: When the +Ve terminal of the battery is connected to P-type material & -

Ve terminal to N-type terminal as shown in the circuit diagram, the diode is said to be forward biased.

The application of forward bias voltage will force electrons in N-type and holes in P-type material to

recombine with the ions near boundary and to flow crossing junction. This reduces width of depletion

region. This further will result in increase in majority carriers flow across the junction. If forward bias is

further increased in magnitude the depletion region width will continue to decrease, resulting in

exponential rise in current as shown in diode characteristic curve.

[2]Reverse-biased: If the negative terminal of battery (DC power supply) is connected with P-type

terminal of diode and +Ve terminal of battery connected to N type then diode is said to be reverse biased.

In this condition the free charge carriers (i.e. electrons in N-type and holes in P-type) will move away

from junction widening depletion region width. The minority carriers (i.e. –ve electrons in p-type and

+ve holes in n-type) can cross the depletion region resulting in minority carrier current flow called as

reverse saturation current(Is). As number of minority carrier is very small so the magnitude of Is is few

microamperes. Ideally current in reverse bias is zero.

Page 7

1 KΩ

(0-30 V)

(0-50 mA)

(0-1 V) 1N 4007

1 KΩ (0-250 µA)

(0-20 V) 1N 4007 (0-30 V)

A

K

A

K

CIRCUIT DIAGRAM:

FORWARD BIAS:

REVERSE BIAS:

Page 8

A

V

A

V

In short, current flows through diode in forward bias and does not flow through diode in reverse bias.

Diode can pass current only in one direction.

Knee Voltage:

It is defined as the forward voltage at which the current through the junction starts increasing rapidly. For

a Silicon diode it is 0.6V and for Germanium diode it is 0.2V.

Break Down Voltage (VBR):

It is defined as the reverse voltage at which PN junction breaks down with sudden increase in reverse

saturation current. This breakdown voltage depends on width of the depletion layer (i.e. Doping level).

Reverse Saturation Current (Is or Io):

This reverse saturation current is due to the flow of minority carriers across the junction when connected

in reverse bias configuration. It is of the order of microamperes for germanium and nanoamperes for

silicon.

PROCEDURE:

FORWARD BIAS:

1. Connections are made as per the circuit diagram.

2. For forward bias, the RPS +ve is connected to the anode of the diode and RPS –ve is

connected to the cathode of the diode

3. Switch on the power supply and increases the input voltage (supply voltage) in steps.

4. Note down the corresponding current flowing through the diode and voltage across the diode

for each and every step of the input voltage.

5. The reading of voltage and current are tabulated.

6. Graph is plotted between voltage and current.

Page 9

MODEL GRAPH:

TABULAR COLUMN:

FORWARD BIAS:

S.No. Voltage across the diode

in Volts

Current through the diode in

mA

Page 10

CALCULATIONS:

FORWARD BIAS:

1. Static Resistance =

2. Dynamic Resistance =

3. Cut-in Voltage =

REVERSE BIAS:

1. Connections are made as per the circuit diagram

2. For reverse bias, the RPS is connected to the cathode of the diode and RPS –ve is connected to the

anode of the diode.

3. Switch on the power supply and increase the input voltage (supply voltage) in steps

4. Note down the corresponding current flowing through the diode voltage across the diode for each and

every step of the input voltage.

5. The readings of voltage and current are tabulated


Page 11

REVERSE BIAS:


in Volts


µA

Page 12

RESULT:

Thus the V–I characteristics of given PN junction diode is studied and the following parameters are

calculated from forward bias condition.

1. Cut-in voltage of the given diode =

2. Static resistance (RS) =


Page 13


(AUTONOMOUS)

DEPT. OF ECE


ZENER DIODE CHARACTERISTICS

AIM:

To verify the V-I Characteristics of given Zener diode and also to find the Cut-in Voltage, Zener

breakdown Voltage, Static Resistance and Dynamic Resistance.

APPARATUS REQUIRED:

1. Zener diode – 1N 3008 --------------- 1No.

2. Resistor – 1KΏ --------------- 1No.

3. Bread Board --------------- 1No.

4. Voltmeter (0-1V, 0-20V) --------------- 1No.

5. Ammeter (0-50mA, 0-250µA) --------------- 1No.

6. Regulated Power Supply (0-30V) ---------------- 1N0.


FORMULAE:



THEORY:

A Zener diode is also called a voltage regulator or breakdown diode. The zener diode is a silicon PN

junction device, which differs from a rectifier diode, in the sense, that it is operated in the reverse break

down region. The breakdown voltage of a zener diode is set by carefully controlling the doping level

during manufacture. When a reverse voltage across a diode is increased, a critical voltage called

breakdown voltage is reached at which the reverse current increases sharply as shown in the model graph.

The reverse breakdown of a PN junction may occur either due to avalanche or zener effect. The

avalanche breakdown occurs, when the accelerated free electrons acquire sufficient energy to ionize a

lattice atom by bombardment. The additional free electrons, created in this way, are accelerated by the

reverse field causing more and more ionization. The multiplication of the number of free carriers causes

the reverse current to increase rapidly.

The zener diodes, with breakdown voltages of less than 6V, operate predominantly in zener breakdown.

Those with breakdown, voltages greater than 6V, operate predominantly in avalanche breakdown.

Page 15

1 KΩ

(0-30 V)

(0-50 mA)

(0-1 V) 1N 3008

1 KΩ (0-250 µA)

(0-20 V)

1N 3008 (0-30 V)

A

K

A

K

CIRCUIT DIAGRAM:

FORWARD BIAS:

REVERSE BIAS:

Page 16

A

V

A

V

PROCEDURE:

FORWARD BIAS:



connected to the cathode of the diode






REVERSE BIAS:


2. For reverse bias, the RPS is connected to the cathode of the diode and RPS –ve is connected

to the anode of the diode.

3. Switch on the power supply and increase the input voltage (supply voltage) in steps

4. Note down the corresponding current flowing through the diode voltage across the diode for

each and every step of the input voltage.

5. The readings of voltage and current are tabulated


Page 17

MODEL GRAPH:

TABULAR COLUMN:

FORWARD BIAS:


in Volts


mA

Page 18

CALCULATIONS:

FORWARD BIAS:



3. Cut in Voltage =

REVERSE BIAS:



3. Breakdown Voltage =

Page 19

REVERSE BIAS:


in Volts


µA

Page 20

RESULT:

Thus the V–I characteristics of given Zener diode is verified and the Breakdown voltage of the given

diode is calculated as _____________ from reverse bias condition.

Page 21


(AUTONOMOUS)

DEPT. OF ECE


====================================================================

HALF WAVE RECTIFIER WITH AND WITHOUT FILTER

AIM:

To obtain the ripple factor and percentage of regulation of half wave rectifier with and without filter.

APPARATUS:

1. Transformer (230 V/ 12 V) --------------- 1No.

2. PN junction Diode (IN4007) --------------- 1No.

3. Bread Board --------------- 1No.

4. Multi Meter --------------- 1No.

5. Capacitor- 100 µF --------------- 1No.

6. Decade Resistor Box ---------------- 1N0.

7. CRO ---------------- 1N0.


FORMULAE:

1. Ripple Factor =

2. % Regulation =

THEORY:

In half wave rectifier, rectifying element conducts only during positive half cycle of input a.c supply. The

negative half cycle of a.c supply are eliminated from the output.

This rectifier circuit consists of resistive load, rectifying element, i.e. p-n junction diode, and the source

of a.c voltage, all connected in series. The circuit diagram is shown in fig usually, the rectifier circuits are

operated from ac mains supply. To obtain the desired dc voltage across the load, the ac voltage is applied

to rectifier circuit using suitable step-up or step-down transformer, mostly a step-down one, with

necessary turns ratio.

The input voltage to the half-wave rectifier circuit shown in the fig is a sinusoidal ac voltage, having a

frequency which is the supply frequency, 50 Hz. Assume that, under reverse biased condition, the diode

acts almost as an open circuit, conducting no current.

Page 23

1N 4007

(0-20 V) (0-20 V) RL

12 V

0 V

1N 4007

(0-20 V) (0-20 V) RL

12 V

0 V

100 µF

K A

A K

CIRCUIT DIAGRAM:

WITHOUT FILTER:

WITH FILTER:

Page 24

To CRO 230 V

AC Supply

To CRO 230 V

AC Supply

PROCEDURE:


2. Switch on the supply and note down the reading of AC input voltage in secondary of

transformer and rectified DC voltage without connecting the load resistor (No load voltage).

3. Vary the load in convenient steps and note down DC & AC voltages

4. Connect the capacitor filter and repeat the step 3 for different values of load resistance

5. Calculate the ripple factor and % of regulation from the obtained readings

6. Draw the input and output waveforms of rectifier (with & without filter )

7. Draw the graph between

(i) a. Load resistance and ripple factor by using without filter

b. Load resistance and ripple factor by using with filter

(ii) a. Load resistance and % of regulation by using without filter.

b. Load resistance and % of regulation by using with filter

Page 25

TABULAR COLUMN:

WITH FILTER:

VNL (No Load Voltage) =

S.No. Vdc in Volts Vac in Volts RL in KΩ Γ =

% Regulation =

WITHOUT FILTER:



% Regulation =

Page 26

CALCULATIONS:

1. Ripple factor without filter is =

2. Ripple factor with filter is =

3. % of Regulation without filter is =

4. % of Regulation with filter is =

Page 27

RL

Rip

ple

Fact

or

RL

% R

egu

lati

on

RL

Rip

ple

Fact

or

RL

% R

egu

lati

on

MODEL GRAPH:

OUTPUT WITHOUT FILTER:

OUTPUT WITH FILTER:-

WITHOUT FILTER:

WITH FILTER:

Page 28

RESULT:

Thus the experiment on Half Wave Rectifier is completed and the following parameters are calculated.

1. Ripple factor Without filter is =

2. Ripple factor With filter is =



Page 29


(AUTONOMOUS)

DEPT. OF ECE


FULL WAVE RECTIFIER WITH AND WITHOUT FILTER

AIM:

To obtain the ripple factor and percentage of regulation of center tapped full wave rectifier with and

without filter.

APPARATUS:

1. Transformer (230 V/ 12-0-12 V) --------------- 1No.

2. PN junction Diode (IN4007) --------------- 2No.

3. Bread Board --------------- 1No.

4. Multi Meter --------------- 1No.

5. Capacitor- 100 µF --------------- 1No.

6. Decade Resistor Box ---------------- 1N0.

7. CRO ---------------- 1N0.


FORMULAE:

1. Ripple Factor =

2. % Regulation =

THEORY:

The circuit of a center-tapped full wave rectifier uses two diodes D1& D2. During positive half cycle of

secondary voltage (input voltage), the diode D1 is forward biased and D2is reverse biased.

The diode D1 conducts and current flows through load resistor RL. During negative half cycle, diode D2

becomes forward biased and D1 reverse biased. Now, D2 conducts and current flows through the load

resistor RL in the same direction. There is a continuous current flow through the load resistor RL, during

both the half cycles and will get unidirectional current as show in the model graph. The difference

between full wave and half wave rectification is that a full wave rectifier allows unidirectional (one way)

current to the load during the entire 360 degrees of the input signal and half-wave rectifier allows this

only during one half cycle (180 degree).

Page 31

1N 4007

(0-20 V) (0-20 V)

RL

12 V

12 V

A K

0 V

A

A K

D1

D2

1N 4007

(0-20 V) (0-20 V)

12 V

12 V

A K

0 V

A

A K

D1

D2 100 µF

CIRCUIT DIAGRAM:

WITHOUT FILTER:

WITH FILTER:

Page 32

To CRO

230 V

AC Supply

To CRO

230 V

AC Supply

RL

PROCEDURE:

1. Connect the Wires in circuit as shown in the figure

2. Switch on the supply and note down the reading of DC input voltage in secondary of

transformer and rectified DC voltage without connecting the load resistor

3. Vary the load in convenient steps and note down rectified DC&AC voltage

4. Connect the capacitor filter and repeat the step 3 for different values of load resistance

5. Calculate the ripple factor and % of regulation from the obtained readings

6. Draw the input and output waveforms of rectifier (with & without filter)

7. Draw the graph between

(i) a. Load resistance and ripple factor by using without filter

b. Load resistance and ripple factor by using with filter

(ii) a. Load resistance and % of regulation by using without filter.

b. Load resistance and % of regulation by using with filter

Page 33

TABULAR COLUMN:

WITH FILTER:



% Regulation =

WITHOUT FILTER:



% Regulation =

Page 34

CALCULATIONS:





Page 35

RL

Rip

ple

Fact

or

RL

% R

egu

lati

on

RL

Rip

ple

Fact

or

RL

% R

egu

lati

on

MODEL GRAPHS:

OUTPUT WITHOUT FILTER:

OUTPUT WITH FILTER:

WITHOUT FILTER:

WITH FILTER:

Page 36

RESULT:

Thus the experiment on center tapped full wave rectifier is completed and the following parameters are

calculated.





Page 37


(AUTONOMOUS)

DEPT. OF ECE


BJT CHARACTERISTICS (CE CONFIGURATION)

AIM:

1. To draw the input and output characteristics of transistor connected in CE configuration.

2. To find Ri, Ro and β of the given transistor configuration.

APPARATUS:

1. Transistor (BC 547) --------------- 1No.

2. Regulated Power Supply (0-30 V) --------------- 1No.

3. Bread Board --------------- 1No.

4. Voltmeter (0-20 V, 0-1 V) --------------- EACH 1 No.

5. Ammeter (0-500 µA, 0-500 mA) --------------- EACH 1No.

6. Resistor (1 KΩ) ---------------- 1N0.


FORMULAE:

1. Input Resistance Ri =

2. Output Resistance Ro =

3. Amplification Factor β =

THEORY:

A transistor is a three terminal device. The terminals are emitter, base, collector. In common emitter

configuration, input voltage is applied between base and emitter terminals and output is taken across the

collector and emitter terminals. Therefore the emitter terminal is common to both input and output.

The input characteristics resemble that of a forward biased diode curve. This is expected since the Base-

Emitter junction of the transistor is forward biased.

The output characteristics are drawn between Ic and VCE at constant IB, the collector current varies with

VCE upto few volts only, after this the collector current becomes almost constant, and independent of VCE.

The value of VCE up to which the collector current changes with V CE is known as Knee voltage. The

transistor always operated in the region above Knee voltage, IC is always constant and is approximately

equal to IB. The current amplification factor of CE configuration is given by β =

Page 39

(0-1 V)

(0-20 V)

(0-250 µA) 1 KΩ

E

C

B

(0-200 mA)

(0-20 V)

(0-250 µA) 1 KΩ

E

C

B

VBB

(0-30 V)

VCC

(0-30 V)

VCC

(0-30 V) VBB

(0-30 V)

CIRCUIT DIAGRAM:

INPUT CHARACTERISTICS:

OUTPUT CHARACTERISTICS:

Page 40

BC 547

BC 547

PROCEDURE:

INPUT CHARACTERSTICS:

1. Connect the circuit as per the circuit diagram.

2. For plotting the input characteristics the output voltage VCE is kept constant at 0V and for different

values of VBE, note down the values of IB

3. Repeat the above step by keeping VCE at 1V and 3V.

4. Tabulate all the readings.

5. Plot the graph between VBE and IB for constant VCE

OUTPUT CHARACTERSTICS:

1. Connect the circuit as per the circuit diagram

2. For plotting the output characteristics the input current IB is kept constant at 50μA and for different

values of VCE, note down the values of IC

3. Repeat the above step by keeping IB at 75 μA 100 μA

4. Tabulate all the readings

5. Plot the graph between VCE and IC for constant IB

Page 41

TABULAR COLUMN:


S.No. VCE = 0 V VCE = 1 V VCE = 3 V

VBE(V) IB(μA) VBE(V) IB(μA) VBE(V) IB(μA)

OUTPUT CHARACTARISTICS:

S.No. IB = 50 μA IB = 75 μA IB = 100 μA

VCE(V) IC(mA) VCE(V) ICmA) VCE(V) IC(mA)

Page 42

CALCULATIONS:




Page 43

MODEL GRAPHS:



Page 44

RESULT:

Thus the input and output characteristics of transistor connected in CE configuration is drawn and the

following parameters are calculated.




Page 45


(AUTONOMOUS)

DEPT. OF ECE


====================================================================

BJT CHARACTERISTICS (CB CONFIGURATION)

AIM:

1. To draw the input and output characteristics of transistor connected in CB configuration.

2. To find Ri, Ro and α of the given transistor configuration.

APPARATUS:

1. Transistor (BC 547) --------------- 1No.


3. Bread Board --------------- 1No.

4. Voltmeter (0-20 V, 0-1 V) --------------- 2No.

5. Ammeter (0-50 mA) --------------- 2No.

6. Resistor (1 KΩ) ---------------- 1N0.


FORMULAE:



3. Amplification Factor α =

THEORY:

A transistor is a three terminal device. The terminals are emitter, base, collector. In common base

configuration, input voltage is applied between emitter and base terminals and output is taken across the

collector and base terminals. Therefore the base terminal is common to both input and output.

The input characteristics resemble that of a forward biased diode curve. This is expected since the

Emitter- Base junction of the transistor is forward biased.

The output characteristics are drawn between Ic and VCB at constant IE, the collector current varies with

VCB upto few volts only, after this the collector current becomes almost constant, and independent of VCB.

The current amplification factor of CB configuration is given by α =

Page 47

(0-1 V) (0-20 V)

(0-50 mA) 1 KΩ

VEE

(0-30 V)

VCC

(0-30 V)

C

B

E

(0-20 V)

1 KΩ

C

B

E

(0-50 mA) (0-50 mA)

VEE

(0-30 V)

VCC

(0-30 V)

CIRCUIT DIAGRAM:



Page 48

BC 547

BC 547

PROCEDURE:

INPUT CHARACTERSTICS:


2. For plotting the input characteristics the output voltage VCB is kept constant at 0V and for different

values of VEB, note down the values of IE

3. Repeat the above step by keeping VCB at 1V and 3V.


5. Plot the graph between VEB and IE for constant VCB

OUTPUT CHARACTERSTICS:


2. For plotting the output characteristics the input current IE is kept constant at 10mA and for different

values of VCB, note down the values of IC

3. Repeat the above step by keeping IB at 20mA and 30mA


5. Plot the graph between VCB and IC for constant IE

Page 49

TABULAR COLUMN:


S.No. VCB = 0 V VCB = 1 V VCB = 3 V

VEB(V) IE(mA) VEB(V) IE(mA) VEB(V) IE(mA)

OUTPUT CHARACTARISTICS:

S.No. IE = 10 mA IE = 20 mA IE = 30 mA

VCB(V) IC(mA) VCB(V) ICmA) VCB(V) IC(mA)

Page 50

CALCULATIONS:




Page 51

MODEL GRAPHS:



Page 52

RESULT:

Thus the input and output characteristics of transistor connected in CB configuration is drawn and the





Page 53


(AUTONOMOUS)

DEPT. OF ECE


FET CHARACTERISTICS (CS CONFIGURATION)

AIM:

1. To draw the drain and transfer characteristics of JFET connected in CS configuration.

2. To find rd, gm and µ of the given JFET.

APPARATUS:

1. JFET (BFW 10/11) --------------- 1No.


3. Bread Board --------------- 1No.

4. Voltmeter (0-20 V) --------------- 2No.

5. Ammeter (0-50 mA) --------------- 1No.

6. Resistor (1 KΩ) ---------------- 1N0.


FORMULAE:

1. Drain Resistance rd =

2. Trans Conductance gm =

3. Amplification Factor µ = rd x gm

THEORY:

A JFET consists of a P- type or N- type silicon bar. The bar is the conducting channel for the charge

carriers. If the bar is made up of N- type material then it is known as N channel FET and if the bar is

made up of P- type material then it is known as P channel FET. There are three terminals in FET namely

Source, Gate and Drain. In JFET, the gate to source voltage is always reverse biased.

When a reverse voltage VGS is applied between the gate and source, the width of the depletion layer is

increased. Thus reduces the width of the channel thereby increases the resistance of N- type bar, as a

result the current from drain to source is decreased.

Page 55

(0-20 V) (0-20 V)

1 KΩ

S

D

G

(0-50 mA)

VGG

(0-30 V)

VDD

(0-30 V)

CIRCUIT DIAGRAM:

Page 56

BFW10/11

PROCEDURE:

DRAIN CHARACTERSTICS:


2. For plotting the drain characteristics the input voltage VGS is kept constant at 0V and for different

values of VDS, note down the values of ID

3. Repeat the above step by keeping VGS at 0.5V and 1V.


5. Plot the graph between VDS and ID for constant VGS

TRANSFER CHARACTERSTICS:


2. For plotting the transfer characteristics the output voltage VDS is kept constant at 5 V and for

different values of VGS, note down the values of ID


4. Plot the graph between VGS and ID for constant VDS

Page 57

TABULAR COLUMN:

DRAIN CHARACTERISTICS:

S.No. VGS = 0 V VGS = - 0.5 V VGS = - 1 V

VDS(V) ID(mA) VDS(V) ID(mA) VDS(V) ID(mA)

TRANSFER CHAREACTARISTICS:

S.No. VDS = 5 V

VGS(V) ID(mA)

Page 58

CALCULATIONS:


2. Transconductance gm =

3. Amplification Factor µ = rd x gm

Page 59

MODEL GRAPHS:

DRAIN CHARACTERISTICS:

TRANSFER CHARACTERISTICS:

Page 60

RESULT:

Thus the drain and transfer characteristics of JFET connected in CS configuration is drawn and the



2. Transconductance gm =

3. Amplification Factor µ =

Page 61


(AUTONOMOUS)

DEPT. OF ECE


UJT CHARACTERISTICS

AIM:

To obtain the characteristics of UJT and to determine the intrinsic stand off ratio.

APPARATUS:

1. UJT (2N2646) --------------- 1No.


3. Bread Board --------------- 1No.

4. Voltmeter (0-20 V) --------------- 2No.

5. Ammeter (0-50 mA) --------------- 1No.

6. Resistor (1 KΩ) ---------------- 1N0.


FORMULAE:

1. Intrinsic stand off ratio ƞ =

THEORY:

A Uni-Junction Transistor (UJT) is an electronic semiconductor device that has only one junction. The

Uni-Junction Transistor (UJT) has three terminals, an emitter (E) and two bases (B1 and B2). The base is

formed by lightly doped n-type bar of silicon. Two ohmic contacts B1 and B2 are attached at its ends.

The emitter is of p-type and it is heavily doped. The resistance between B1 and B2, when the emitter is

open-circuit is called inter-base resistance. The original uni-junction transistor, or UJT, is a simple

device that is essentially a bar of N type semiconductor material into which P type material has been

diffused somewhere along its length. The 2N2646 is the most commonly used version of the UJT.

PROCEDURE:


2. Keep the base to base voltage VBB constant.

3. Vary the emitter voltages in convenient steps and note down the emitter current.

4. Repeat the above steps for different constant base to base voltages VBB.

5. Plot the graph between VEB and IE for constant VBB.

Page 63

(0-20 V) (0-20 V)

1 KΩ

B1

B2 E

(0-50 mA)

RPS 1

(0-30 V)

RPS 2

(0-30 V)

CIRCUIT DIAGRAM:

TABULAR COLUMN:

S.No. VBB = 7 V VBB = 5 V VBB = 3 V

VEB(V) IB(mA) VEB(V) IB(mA) VEB(V) IB(mA)

Page 64

BFW10/11

CALCULATIONS:

1. Intrinsic stand off ratio ƞ =

Page 65

MODEL GRAPH:

Page 66

RESULT:

Thus the characteristics of UJT are obtained and the intrinsic stand off ratio is calculated as

_______________.

Page 67


(AUTONOMOUS)

DEPT. OF ECE


====================================================================

LED CHARACTERISTICS

AIM:

To verify the characteristics of Light Emitting Diode (LED) and determine the cut- in voltage.

APPARATUS REQUIRED:

1. LED --------------- 1No.

2. Resistor – 1KΏ --------------- 1No.

3. Bread Board --------------- 1No.

4. Voltmeter (0-20V) --------------- 1No.

5. Ammeter (0-50mA) --------------- 1No.

6. Regulated Power Supply (0-30V) ---------------- 1N0.


THEORY:

LED is semiconductor junction diode which emits light when current passes through it in forward bias

condition. P type of semiconductor consists of large number of holes while N type of semiconductor

consists of large number of electrons. At zero bias (no voltage across junction), depletion region exists

and it separate out two regions. When LED is forward biased, barrier potential reduces and depletion

region becomes narrow. Electron crosses the depletion region and recombines with holes.

Similarly holes crosses depletion region and recombine with electrons. Each recombination of hole and

electron produces photon (light) The intensity of light emitted depends on the number of minority carriers

available for recombination. Wavelength (or frequency) of emitted light depends on band-gap energy.

The light emitting diode works by the process of spontaneous emission.

Light source materials are made from compound of group-III (Al,Ga,In) and group-V (P,As,Sb)

element.The wavelength generated by the LED depends on bandgap energy and bandgap energy depends

on doping level of above elements.

Page 69

1 KΩ

(0-30 V)

(0-50 mA)

(0-20 V)

A

K

CIRCUIT DIAGRAM:

MODEL GRAPH:

TABULAR COLUMN:


in Volts


mA

Page 70

A

V

V

I

PROCEDURE:



connected to the cathode of the diode,






RESULT:

Thus the characteristics of given LED is verified and the cut- in voltage is calculated as

_______________.

Page 71


(AUTONOMOUS)

DEPT. OF ECE


====================================================================

V-I CHARACTERISTIC OF SCR

AIM:

To obtain the V-I characteristics of SCR and find the break over voltage and holding current.

APPARATUS REQUIRED:

1. SCR (TYN604) ----------------- 1No.

2. Resistors- (330 Ω, 100 Ω) ----------------- Each 1No.

3. Voltmeter (0-30 V) --------------- 1. No.

4. Ammeter (0-100 mA, 0-50 mA) --------------- EACH 1No.

5. Diode 1N4007 ----------------- 1No.

6. Regulated Power Supply (0-30 V) ----------------- 1No.

7. Breadboard ----------------- 1No.


THEORY:

A silicon controlled rectifier (SCR) is a semiconductor device that acts as a true electronic switch. It can

change the alternating current in to direct current. It can control the amount of power fed to the load.

Thus the SCR combines the features of rectifier and a transistor. If the supply voltage is less than the

break over voltage, the gate will open (IG = 0). Then increase the supply voltage from zero, a point is

reached when the SCR starts conducting. Under this condition, the voltage across the SCR suddenly drop

and most of the supply voltage appears across the load resistance RL. If proper gate current is made to

flow the SCR can close at much smaller supply voltage.

Page 73

CIRCUIT DIAGRAM:

Page 74

PROCEDURE:

1. The connections are made as per in the circuit diagram.

2. First by varying RPS 2 then gate current (IG) is kept constant.

3. The voltage between anode and cathode is increased in step by step by varying the RPS 1.

4. The corresponding anode current (IA) is noted.

5. The process is repeated for two more constant value of IG, the readings are tabulated.

Page 75

TABULAR COLUMN:

S. No.

AnodeCathode

Voltage Vak

(Volts)

Gate Current Ig

(mA)

Anode Current

Ia (mA)

Anode –

Cathode volt

when SCR in

ON (volts)

Page 76

MODEL GRAPH:

RESULT:

Thus the V-I characteristics of SCR was obtained and graph was drawn.

Page 77

electronic devices and circuits lab manual (17aec07) … · scr characteristics . index s. no. date...

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