Edc 2

LAB-MANUAL

II Year III SEM ECE

3EC-09

Electronics Lab I

ACERC/Department of ECE/EDC lab/1

DEPARTMENT OF ELECTRONICS & COMMUNICATION

ENGINEERING


INDEXS. No. Content Page

No.1. RTU syllabus2. Do’s and Don’ts

3. Instructions to the Students4. Lab PEO5. Lab Plan

Experiment as per RTU Syllabus

1.

1. Exp-1 Study the following devices:(a) Analog & digital multimeters(b) Function/ Signal generators(c) Regulated d. c. power supplies (constant voltage and constant current operations)(d) Study of analog CRO, measurement of time period, amplitude, frequency & phase angle using Lissajous figures.

2. Exp-2 Plot V-I characteristic of P-N junction diode & calculate cut-in voltage, reverse Saturation current and static & dynamic resistances.

3.Exp-3 Plot V-I characteristic of zener diode and study of zener diode as voltage regulator. Observe the effect of load changes and determine load limits of the voltage regulator.

4. Exp-4 Plot frequency response curve for single stage amplifier and to determine gain bandwidth product.

5. Exp-5 Plot drain current - drain voltage and drain current – gate bias characteristics of field effect transistor and measure of Idss & Vp.

6. Exp-6 Application of Diode as clipper & clamper.

7.Exp-7 Plot gain- frequency characteristic of two stages RC coupled amplifier & calculate its bandwidth and compare it with theoretical value.

8. Exp-8 Plot gain- frequency characteristic of emitter follower & find out its input and output resistances.

9.Exp-9 Plot input and output characteristics of BJT in CB, CC and CE configurations. Find their h- parameters.

10. Exp-10 Study half wave rectifier and effect of filters on wave. Also calculate theoretical & practical ripple factor.

11. Exp-11 Study bridge rectifier and measure the effect of filter network on D.C. voltage output & ripple.

Experiment Beyond Syllabus


1. Exp-1 To find the Ripple factor and regulation of a Full-wave Rectifier with and without filter.

2. Exp-2 To observe the characteristics of UJT and to calculate the Intrinsic Stand-Off Ratio (η).

3. Exp-3 To draw the V-I Characteristics of SCR

RTU Detailed Syllabus


Class: III Sem. B. Tech. EvaluationBranch: ECESchedule per WeekPractical Hrs : 3

Examination Time = Three (4) HoursMaximum Marks = 100[ Sessional (60) & End-term (40)]

S. No.

List of Experiments

1 2. Study the following devices:(a) Analog & digital multimeters(b) Function/ Signal generators(c) Regulated d. c. power supplies (constant voltage and constant current operations)(d) Study of analog CRO, measurement of time period, amplitude, frequency & phase angle using Lissajous figures.

2 Plot V-I characteristic of P-N junction diode & calculate cut-in voltage, reverse Saturation current and static & dynamic resistances.

3 Plot V-I characteristic of zener diode and study of zener diode as voltage regulator. Observe the effect of load changes and determine load limits of the voltage regulator

4 Plot frequency response curve for single stage amplifier and to determine gain bandwidth product

5 Plot drain current - drain voltage and drain current – gate bias characteristics of field effect transistor and measure of Idss & Vp.

6 Application of Diode as clipper & clamper.

7 Plot gain- frequency characteristic of two stages RC coupled amplifier & calculate its bandwidth and compare it with theoretical value.

8 Plot gain- frequency characteristic of emitter follower & find out its input and output resistances.

9 Plot input and output characteristics of BJT in CB, CC and CE configurations. Find their h- parameters.

10 Study half wave rectifier and effect of filters on wave. Also calculate theoretical & practical ripple factor.

11 Study bridge rectifier and measure the effect of filter network on D.C. voltage output & ripple.


DO’S AND DON’T’S

DO’S

1. Student should get the record of previous experiment checked before starting the

new experiment.

2. Read the manual carefully before starting the experiment.

3. Before starting the experiment, get circuit diagram checked by the teacher.

4. Before switching on the power supply, get the circuit connections checked.

5. Get your readings checked by the teacher.

6. Apparatus must be handled carefully.

7. Maintain strict discipline.

8. Keep your mobile phone switched off or in vibration mode.

9. Students should get the experiment allotted for next turn, before leaving the lab.

DON’TS

1. Do not touch or attempt to touch the mains power supply Wire with bare hands.

2. Do not overcrowd the tables.

3. Do not tamper with equipments.

4. Do not leave the without permission from the teacher


INSTRUCTIONS TO THE STUDENTS

GENERAL INSTRUCTIONS

Maintain separate observation copy for each laboratory.

Observations or readings should be taken only in the observation copy.

Get the readings counter signed by the faculty after the completion of the experiment.

Maintain Index column in the observation copy and get the signature of the faculty

before leaving the lab.

BEFORE ENTERING THE LAB

The previous experiment should have been written in the practical file, without

which the students will not be allowed to enter the lab.

The students should have written the experiment in the observation copy that they

are supposed to perform in the lab.

The experiment written in the observation copy should have aim, apparatus

required, circuit diagram/algorithm, blank observation table (if any), formula (if

any), programmed (if any), model graph (if any) and space for result.

WHEN WORKING IN THE LAB

Necessary equipments/apparatus should be taken only from the lab assistant by

making an issuing slip, which would contain name of the experiment, names of

batch members and apparatus or components required.

Never switch on the power supply before getting the permission from the faculty.

BEFORE LEAVING THE LAB

The equipments/components should be returned back to the lab assistant in good

condition after the completion of the experiment.

The students should get the signature from the faculty in the observation copy.

They should also check whether their file is checked and counter signed in the

index.

Program Educational Objectives: ACERC/Department of ECE/EDC lab/7

1. EDC Lab is an important Lab for all the students as they make different circuits on breadboard which includes various devices such as Transistors, Diodes, and Amplifiers etc. It is important to understand the basics and working of these devices.

2. It is the basic Lab of all the branches… Knowledge and concept of electrons and holes, Diode, semiconductors, Amplifiers are necessary in each and every subject. Of Electronics. Which is useful for understanding the behavior of different electronics devices?

3. This Lab helps in understanding various other Labs, of electronics, real life application.

4. In industries the practical application uses the basic Knowledge of EDC. During Training, the student see a lot of equipment having devices like Diode, Capacitor, Transistor, MOSFET, PCB Designing , Testing , so the basic Knowledge about them lead to easy understanding of their working.

5. This Lab helps to understand the important of Electronics in Social life. Device Miniaturization is become of EDC only.. Use of LED, LCD, Sensor and Various Opto electronics devices can be easily understood because of Electronics only.

3. Program Outcomes:

A) Graduate will have the basic knowledge of Electronics, device and circuits.

B) Graduate will have an ability to identify the various devices, working Principle, Characteristics and their applications.

C) Graduate will have an ability to design various Projects, PCB design and working of daily Use Equipment (Like: LED, sensors, Opto electronics devices).

D) The knowledge Of EDC Lab will help the student to perform various Experiments in Laboratories which will help in understanding theory more clearly.

E) Graduate will have the Knowledge and use of Modern Upcoming technologies Like Mobile, 3G, 4G Technologies which will help in complete development of student.

F) The Knowledge of EDC Lab will help in getting Success in Research and Development.

G) Graduate will develop confidence for getting higher education and ability of Life Long learning.

H) Graduate will show the understanding of impact of Engineering Solution on the society and also will be aware of Contemporary issue.

I) This Lab help in Preparing student for various industries purpose such as Knowledge of PCB designing, Testing and Circuit Forming.


J) The Lab knowledge helps in professional and developing Ethical responsibilities.

K) This Lab will help in understanding of various other subjects of Engineering Stream such as Digital Electronics, Microprocessor and Analog Electronics.

3. Mapping of course objective with course Outcomes

Program Objectives/Outcomes

A B C D E F G H I J K

I Yes Yes Yes Yes Yes Yes Yes

II Yes Yes Yes Yes Yes Yes

III Yes Yes Yes Yes Yes Yes Yes

IV Yes Yes Yes Yes Yes Yes

V Yes Yes Yes Yes Yes

4. Important Topics Covered:

Study of CRO and Function Generators etc

Semiconductor Physics and PN Diode I/p and O/p Characteristics..

Zener Diode Characteristics

Clipper and Clamper

Rectifier (Half Wave and Full Wave)

BJT Transistor I/p and O/p Characteristics..

Single Stage Amplifier

Emitter Follower

RC Couple Amplifier

FET I/p and O/p Characteristics..

5. Topics beyond the Syllabus:

1) Foundation Topics:

Introduction of Conductors, Semiconductor and Insulators

Diode, Transistors Operation and applications


FET, MOSFET Operation and applications

2) Advanced Topics:

Zener and Avalanche Breakdown

Feedback Concepts

Rectifiers

Study of CRO and Function Generators etc

3) Contemporary Issues/Trends

Advancement in the designing of Electronics Circuits on Printed Circuit Board.

4) New Application Oriented Topics

Feedback Topology

Oscillators

6. Text Book/Reference Book

S.No Title Author Publication

1 Electronics Device and Circuits

Milliman Hallkias Tata McGraw hill Publications


Robert Bolystead Pearson Prentice Hall


Sanjeev Gupta Dhanpat Rai Publications


J.B.Gupta S.K. Kataria & Sons

LAB PLAN-


DATE/EXP. No. 1 2 3 4 5 6 7 8 9 10

Experiment no. 1 G1 G2 G3 G4 G5











1. STUDY OF DEVICES

AIM: - Study the following devices:

(a) Analog & digital multimeters(b) Function/ Signal generators(c) Regulated d. c. power supplies (constant voltage and constant current operations)(d) Study of analog CRO, measurement of time period, amplitude, frequency & phase angle using Lissajous figures.

APPARATUS:-

CROAnalog and digital multimeterFunction / Signal GeneratorRegulated DC Power SupplyCRO Probes

THEORY:-

(a) ANALOG AND DIGITAL MULTIMETER

A multimeter or a multitester, also known as a VOM (Volt-Ohm meter), is an electronic

measuring that combines several measurement functions in one unit. A typical multimeter may

include features such as the ability to measure voltage, current and resistance. Multimeters may

use analog or digital circuits—analog multimeters (AMM) and digital multimeters (often

abbreviated DMM or DVOM.) Analog instruments are usually based on a micro ammeter whose

pointer moves over a scale calibrated for all the different measurements that can be made; digital

instruments usually display digits, but may display a bar of a length proportional to the quantity

being measured.

A multimeter can be a hand-held device useful for basic fault finding and field service work or

a bench instrument which can measure to a very high degree of accuracy. They can be used to

troubleshoot electrical problems in a wide array of industrial and household devices such

as electronic equipment, motor controls, domestic appliances, power supplies, and wiring systems


http://en.wikipedia.org/wiki/Power_supply

http://en.wikipedia.org/wiki/Domestic_appliance

http://en.wikipedia.org/wiki/Electronic_equipment

http://en.wikipedia.org/w/index.php?title=Bench_instrument&action=edit&redlink=1

http://en.wikipedia.org/wiki/Fault_(electric)

http://en.wikipedia.org/wiki/Microammeter

http://en.wikipedia.org/wiki/Digital_circuit

http://en.wikipedia.org/wiki/Analog_circuit

http://en.wikipedia.org/wiki/Electric_current

http://en.wikipedia.org/wiki/Voltage

Fig. DIGITAL MULTIMETER

OPERATION

A multimeter is a combination of a multirange DC voltmeter, multirange AC voltmeter,

multirange ammeter, and multirange ohmmeter. An un-amplified analog multimeter combines a

meter movement, range resistors and switches.

For an analog meter movement, DC voltage is measured with a series resistor connected between

the meter movement and the circuit under test. A set of switches allows greater resistance to be

inserted for higher voltage ranges. The product of the basic full-scale deflection current of the

movement, and the sum of the series resistance and the movement's own resistance, gives the full-

scale voltage of the range. As an example, a meter movement that required 1 milliamp for full

scale deflection, with an internal resistance of 500 ohms, would, on a 10-volt range of the

multimeter, has 9,500 ohms of series resistance. For analog current ranges, low-resistance shunts

are connected in parallel with the meter movement to divert most of the current around the coil.

Again for the case of a hypothetical 1 mA, 500 ohm movement on a 1 Ampere range, the shunt

resistance would be just over 0.5 ohms.

Moving coil instruments respond only to the average value of the current through them. To

measure alternating current, a rectifier diode is inserted in the circuit so that the average value of

current is non-zero. Since the average value and the root-mean-square value of a waveform need

not be the same, simple rectifier-type circuits may only be accurate for sinusoidal waveforms.

Other wave shapes require a different calibration factor to relate RMS and average value. Since

practical rectifiers have non-zero voltage drop, accuracy and sensitivity is poor at low values.


http://en.wikipedia.org/wiki/Rectifier

To measure resistance, a small dry cell within the instrument passes a current through the device

under test and the meter coil. Since the current available depends on the state of charge of the dry

cell, a multimeter usually has an adjustment for the ohms scale to zero it. In the usual circuit

found in analog multimeters, the meter deflection is inversely proportional to the resistance; so

full-scale is 0 ohms, and high resistance corresponds to smaller deflections. The ohms scale is

compressed, so resolution is better at lower resistance values.

Amplified instruments simplify the design of the series and shunt resistor networks. The internal

resistance of the coil is decoupled from the selection of the series and shunt range resistors; the

series network becomes a voltage divider. Where AC measurements are required, the rectifier can

be placed after the amplifier stage, improving precision at low range.

Digital instruments, which necessarily incorporate amplifiers, use the same principles as analog

instruments for range resistors. For resistance measurements, usually a small constant current is

passed through the device under test and the digital multimeter reads the resultant voltage drop;

this eliminates the scale compression found in analog meters, but requires a source of significant

current. An auto ranging digital multimeter can automatically adjust the scaling network so that

the measurement uses the full precision of the A/D converter.

In all types of multimeters, the quality of the switching elements is critical to stable and accurate

measurements. Stability of the resistors is a limiting factor in the long-term accuracy and

precision of the instrument.

(b) FUNCTION GENERATOR

Fig. FUNCTION GENERATOR

The function generator is used to generate a wide range of alternating-current (AC) signals.

The front panel is divided into six major control groups:

1) Frequency Selection Group;


http://en.wikipedia.org/wiki/Voltage_divider

2) Sweep Group;

3) Amplitude Modulation Group;

4) DC Offset Group;

5) Function, or Waveform Group; and

6) Output Group.

• The power switch is on the upper left-hand corner of the unit. The green LED will indicate that

the unit is on.

• The three most important groups for this lab are the frequency, function, and output groups. The

remaining three groups, (sweep, amplitude modulation, and DC offset) will be briefly covered in

the lab setup procedures. Should you desire more detailed descriptions of these groups; the Leader

Function Generator manual is available in the lab.

Frequency Selection Group:

These controls are used to select the operating frequency of the function generator. This group

consists of the frequency control knob and the eight frequency multiplier selection buttons. For

example, to set the function generator to an operating frequency of 2000 Hz (2 kHz):

• Rotate the frequency control knob to 2.

• Select the 1 kHz frequency multiplier button.

With the result that: 2.0 * 1 kHz = 2.0 kHz.

To set the function generator to an operating frequency of 5.5 kHz:

• Rotate the frequency control knob to 0.55.

• Select the 10 kHz frequency multiplier button.

With the result that: 0.55 * 10 kHz = 5.5 kHz.

Output Group: ACERC/Department of ECE/EDC lab/15

1. These controls are used to adjust the amplitude of the generator's

output signal. The group consists of the amplitude-control knob, the three attenuation buttons and

the fused 50 ohm BNC connector. Although the amplitude knob is not indexed, the amplitude

ranges from a few millivolts to approximately 20 volts. We will set the amplitude levels by

aligning the white line on the amplitude knob to the three o'clock position (90 degrees right), the

nine o'clock position (90 degrees left), or the twelve o'clock position (straight up). Notice that

rotating the knob fully to the left does not result in a zero amplitude signal.

• The attenuation buttons are used to attenuate (decrease) the amplitude of the signal by a factor

measured in decibels. The following relationship will assist in working with the attenuation

buttons:

(dB) = -10 * log10 (Pout/ Pin) (if power is the unit of measurement) or

(dB) = -20 * log10 (Vout / Vin) (if voltage is the unit of measurement)

Note: The attenuation buttons are additive. In other words, if the 10 dB and the 20 dB buttons are

both pressed in, the combined attenuation of the input signal is 30 dB.

Function/Waveform Selection Group:

This group is used to select the shape of the generated waveform. The group is made up of the six

wave-selector buttons. The six waveforms that the function generator can produce are the sine

wave, the square wave, the triangle wave, two sawtooth waves, and the variable-width pulse

wave.

© Regulated d. c. power supplies (constant voltage and constant current operations)A power supply is a device that supplies electric power to an electrical load. The term is most

commonly applied to devices that convert one form of electrical energy to another, though it may

also refer to devices that convert another form of energy (mechanical, chemical, solar) to

electrical energy. A regulated power supply is one that controls the output voltage or current to a

specific value; the controlled value is held nearly constant despite variations in either load current

or the voltage supplied by the power supply's energy source.


http://en.wikipedia.org/wiki/Regulated_power_supply

http://en.wikipedia.org/wiki/Electrical_load

http://en.wikipedia.org/wiki/Electric_power

Every power supply must obtain the energy it supplies to its load, as well as any energy it

consumes while performing that task, from an energy source. Depending on its design, a power

supply may obtain energy from:

Electrical energy transmission systems. Common examples of this include power supplies

that convert AC line voltage to DC voltage.

Energy storage devices such as batteries and fuel cells.

Electromechanical systems such as generators and alternators.

Solar power.

A power supply may be implemented as a discrete, stand-alone device or as an integral device

that is hardwired to its load. Examples of the latter case include the low voltage DC power

supplies that are part of desktop computers and consumer electronics devices.

Commonly specified power supply attributes include:

The amount of voltage and current it can supply to its load.

How stable its output voltage or current is under varying line and load conditions.

How long it can supply energy without refueling or recharging (applies to power supplies

that employ portable energy sources).

DC power supplyAn AC powered unregulated power supply usually uses a transformer to convert the voltage from

the wall outlet (mains) to a different, nowadays usually lower, voltage. If it is used to

produce DC, rectifier is used to convert alternating voltage to a pulsating direct voltage, followed

by a filter, comprising one or more capacitors, resistors, and sometimes inductors, to filter out

(smooth) most of the pulsation. A small remaining unwanted alternating voltage component at

mains or twice mains power frequency (depending upon whether half- or full-wave rectification is

used)—ripple—is unavoidably superimposed on the direct output voltage.

For purposes such as charging batteries the ripple is not a problem, and the simplest unregulated

mains-powered DC power supply circuit consists of a transformer driving a single diode in series

with a resistor.


http://en.wikipedia.org/wiki/Resistor

http://en.wikipedia.org/wiki/Ripple_(electrical)

http://en.wikipedia.org/wiki/Utility_frequency

http://en.wikipedia.org/wiki/Inductor

http://en.wikipedia.org/wiki/Resistor

http://en.wikipedia.org/wiki/Capacitor

http://en.wikipedia.org/wiki/Electronic_filter

http://en.wikipedia.org/wiki/Direct_current

http://en.wikipedia.org/wiki/Transformer

http://en.wikipedia.org/wiki/Alternating_current

http://en.wikipedia.org/wiki/Current_(electricity)

http://en.wikipedia.org/wiki/Voltage

http://en.wikipedia.org/wiki/Consumer_electronics

http://en.wikipedia.org/wiki/Desktop_computer

http://en.wiktionary.org/wiki/hardwired

http://en.wikipedia.org/wiki/Solar_power

http://en.wikipedia.org/wiki/Alternator

http://en.wikipedia.org/wiki/Electrical_generators

http://en.wikipedia.org/wiki/Fuel_cell

http://en.wikipedia.org/wiki/Battery_(electricity)

http://en.wikipedia.org/wiki/Energy_storage

http://en.wikipedia.org/wiki/Direct_current

http://en.wikipedia.org/wiki/Alternating_current

Before the introduction of solid-state electronics, equipment used valves (vacuum tubes) which

required high voltages; power supplies used step-up transformers, rectifiers, and filters to generate

one or more direct voltages of some hundreds of volts, and a low alternating voltage for filaments.

Only the most advanced equipment used expensive and bulky regulated power supplies.

AC power supplyAn AC power supply typically takes the voltage from a wall outlet (mains supply) and lowers it to

the desired voltage. Some filtering may take place as well.

(d) ANALOG CRO

Technical Specifications Operating Modes:

OPERATING MODES

CH 1, CH 2, CH 1&11 Alt / Chopped,

(Approx. 350 KHz), X-Y operation: 1:1

Vertical Deflection: (Both Channels)

Bandwidth: DC 20 MHz (-3dB)

Rise time: 17.5 ns (approximately)

Deflection Coefficients: 12 steps

5mV/cm - 20V/cm (1-2-5 sequence)

Accuracy: ± 3%

Input Impedance: 1M Ω ||30pF

Input coupling: DC-AC Gnd

Max. Input: 350V (DC+ peak AC)

Time Base:

Time coefficients: 18 steps, 0.5 µs/ cm0.2s/ cm

(1-2-5 sequence) with MagX5 to 100 ns/cm.

With variable to 40ns/cm

Accuracy: ±3 % (In cal position)

Sweep Output: Approximately 5V(peak to peak)

Trigger System:

Modes: Auto or variable

Source: CH 1 or CH 2, external

Slope: Positive or Negative

Coupling: AC, TV frame


http://en.wikipedia.org/wiki/Mains_supply

http://en.wikipedia.org/wiki/Vacuum_tube

http://en.wikipedia.org/wiki/Solid-state_electronics

Sensitivity: Internal 0.5cm External0.8V

Trigger Bandwidth: 40 MHz

HORIZONTAL DEFLECTION

Bandwidth: DC- 2 MHz (-3dB)

XY mode: Phase shift < 5° 60 KHz

Deflection coefficients: 12 calibrated

Steps 5 mV /cm-20V /cm

Input Impedance: 1MΩ || 30 pF

Component Tester:

Test Voltage: Max. 8.6 Vrms

Test Current: Max. 8 mArms

Test Frequency: 50 HZ Test circuit

Ground to chassis

Miscellaneous:

Fault Simulation: Total of 15 faults

Can be simulated. Detailed

Troubleshooting Procedure included.

Cathode ray tube: 140 mm Rectangular

Tube with internal graticule,

(P-31) phosphor

Accelerating potential: 2000 VDC

Display: 8x10 cm

Trace rotation: Adjustable

Calibrator: Square wave 1KHz(approx.) 0.2V +1%

Z Modulation: TTL level

Mains Voltage: 230V ±10% 50Hz

Power Consumption: 36 VA(approximately)

Weight: 7.3 Kg (Approximately)

Dimensions (mm): W450 x H145 x D42

Front Panel Controls


(1) Power ‘On/Off’: Turns ‘On’ & ‘Off’ (on in open cover condition only.) LED indicates power

‘On’. Use position& Int/Focus controls to get the beam. All push buttons.

(2) Time / Div: Rotary Switch for TB speed control.

(3) Trigger Input: For feeding External trigger signal.

(4) Volts/Div: For sensitivity selection of CH 1 & CH 2.

(5) DC-AC-Gnd: Switch provided for Input coupling. BNC inputs provided for connecting the

Input signal.

(6) Component Tester: Switch when pressed converts scope into Component Tester mode.

(7) CT: Input & Gnd terminals to be used for CT.

Controls on PCB

(1) Intensity: Controls the brightness

(2) Focus: Controls the sharpness

(3) Trace Rotation: Controls the horizontal alignment of the trace.

(4) X Pos: Controls the horizontal position

(5) Y Pos I & II: Controls vertical position of the trace.

(6) X Y: When pressed cuts-off internal TB & connects external horizontal signal via. CH II

(7) X 5: When pressed gives 5 times magnification.

(8) External: When pressed allows ext. trigger.

(9) TV: When pressed allows TV frame to be synchronized.

(10) Cal Variable: Controls the time speed in between the steps.


(11) Auto/ Norm: In AT gives display of trace & auto trigger. When pressed becomes normal &

gives variable level trigger.

(12) Level: Controls the trigger level from positive peak to negative peak.

(13) + / - : Selects the slope of triggering.

(14) Trig 1/ Trig 2: When out trigger CH I and when pressed triggers CH II

(15) CH I Alt/: When out selects CH I and when pressed selects

CH II Chop CH II. When dual switch also pressed this selects Alt or Chop modes.

(16) Mono / Dual: When out, selects CH I only. When pressed selects both.

Amplitude Measurements

In general electrical engineering, alternating voltage data normally refers to effective values (rms =

root-mean-square value). However, for signal magnitudes and voltage designations in Oscilloscope

measurements, the peak-to-peak voltage (Vpp) value misapplied. The latter corresponds to the real

potential difference between the most positive and most negative points of a signal waveform. If a

sinusoidal waveform, displayed on the Oscilloscope screen, is to be converted into an effective

(rms) value, the resulting peak-to-peak value must be divided by 2 x√2 = 2.83. Conversely, it

should be observed that sinusoidal voltages indicated in Vrms (Veff) have 2.83 times the potential.

The maximum signal voltage required at the vertical amplifier input for a display of 1cm is

approximately 5mVpp. This is achieved with the attenuator control set at5mV/cm, however smaller

signals than this may also be displayed. The deflection coefficients on the input attenuators are

indicated in mV/cm or V/cm (peak-to-peak value).The magnitude of the applied voltage is

ascertained by multiplying the selected deflection coefficient by the vertical display height in cm. If

an attenuator probe X10is used, a further multiplication by a factor of 10 is required to ascertain the

correct voltage value.

Time Measurements :

As a rule, most signals to be displayed are periodically repeating processes, also called periods.

The number of periods per second is the repetition frequency Depending on the time base setting

of the Time/Div. switch, one or several signal periods or only a part of a period can be displayed.

The time coefficients are stated ins/cm, ms/cm and µs/cm on three fields. There are 18 time

coefficient ranges of the ST2001E, from 0.5s/cm to 0.2s/cm.The duration of a signal period or a

part of it is determined by multiplying the relevant time (horizontal distance in cm) by the time


coefficient set on the Time/Div. switch. The variable time control (identified with an arrow knob

cap) must be in its calibrated position Cal. (arrow pointing horizontally to the left).

Operating Modes :

The required operating modes are selected with push buttons in the vertical amplifier section. For

'Mono' operation with channel I only, all push buttons should be out. For' Mono' operation with

channel 2, only, the 'Alt/Chop' button must be pressed. For internal triggering with the signal from

channel 2, the Trig 1/2 button has to be pressed in addition. On pressing the button marked

'Mono/Dual', dual trace operation is selected. In this condition both traces are displayed

consecutively (alternate sweep).This mode is not suitable for the display of very low frequency

signals as the display will flicker or appear to jump. This can be overcome by pressing the

'Alt/Chop' button. Both channels then share the trace during each sweep period (chopped

mode).For display with a higher repetition rate, the type of channel switching is less important but

the alternate mode is normally suggested. For XY operation the XY button must be pressed. The

X signal is connected via the input of channel 2. The sensitivity of the horizontal amplifier during

X-Y operation is selected by the CH II attenuator switch. The sensitivity and input impedance for

both the X & Y axes are equal. Note that the frequency limit of the X axis is approximately2 MHz

(-3 dB). Therefore, an increase in phase difference is noticeable at higher frequencies. The phase

shift is 3° approximately at 60 KHz. Lissajous figures can be displayed in the X- Y mode for

certain measuring tasks.

• Comparing two signals of different frequency or bringing one frequency up to the frequency of

the other signal. This also applies for whole number multiples or fractions of the one signal frequency.

• Phase comparison between two signals of the same frequency

RESULT: - We successfully studied about analog and digital multimeter, Function generator,

Regulated DC power supply and analog CRO


1. P-N JUNCTION DIODE CHARACTERISTICS

AIM: - Plot V-I characteristic of P-N junction diode & calculate cut-in voltage, reverse Saturation current and static & dynamic resistances.

APPARATUS:-

P-N Diode IN4007. Regulated Power supply (0-30v) Resistor 1KΩ Ammeters (0-200 mA, 0-500mA) Voltmeter (0-20 V) Bread board Connecting wires

THEORY:-

A p-n junction diode conducts only in one direction. The V-I characteristics of the diode are curve

between voltage across the diode and current through the diode. When external voltage is zero,

circuit is open and the potential barrier does not allow the current to flow. Therefore, the circuit

current is zero. When P-type (Anode is connected to positive terminal and n- type (cathode) is

connected to negative terminal of the supply voltage, is known as forward bias. The potential

barrier is reduced when diode is in the forward biased condition. At some forward voltage, the

potential barrier altogether eliminated and current starts flowing through the diode and also in

the circuit. The diode is said to be in ON state. The current increases with increasing forward

voltage.

When N-type (cathode) is connected to positive terminal and P-type (Anode) is connected

negative terminal of the supply voltage is known as reverse bias and the potential barrier across

the junction increases. Therefore, the junction resistance becomes very high and a very small

current (reverse saturation current) flows in the circuit. The diode is said to be in OFF state. The

reverse bias current produces due to minority charge carriers.


CIRCUIT DIAGRAM:-

FORWARD BIAS:-

REVERSE BIAS:-


MODEL WAVEFORM:-

PROCEDURE:-

FORWARD BIAS:-

1. Connections are made as per the circuit diagram.

2. For forward bias, the RPS positive is connected to the anode of the diode and RPS negative 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.

OBSERVATION:-

S.NO APPLIED VOLTAGE (V) VOLTAGE ACROSS

DIODE(V)

CURRENT

THROUGH

DIODE(mA)

PROCEDURE:-

REVERSE BIAS:-

1. Connections are made as per the circuit diagram

2. For reverse bias, the RPS positive is connected to the cathode of the diode and RPS negative 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.

6. Graph is plotted between voltage and current.

OBSEVATION:-

S.NO APPLIEDVOLTAGE

ACROSSDIODE(V)

VOLTAGE

ACROSS DIODE(V)

CURRENT

THROUGH


DIODE(mA)

PRECAUTIONS:-

1. All the connections should be correct.

2. Parallax error should be avoided while taking the readings from the Analog meters.

RESULT: - Forward and Reverse Bias characteristics for a p-n diode is observed

VIVA QESTIONS:-

1. Define depletion region of a diode?

2. What is meant by transition & space charge capacitance of a diode?

3. Is the V-I relationship of a diode Linear or Exponential?

4. Define cut-in voltage of a diode and specify the values for Si and Ge diodes?

5. What are the applications of a p-n diode?

6. Draw the ideal characteristics of P-N junction diode?

7. What is the diode equation?

8. What is PIV?

9. What is the break down voltage?

10. What is the effect of temperature on PN junction diodes?


2. ZENER DIODE CHARACTERISTICS

AIM: Plot V-I characteristic of zener diode and study of zener diode as voltage regulator.

Observe the effect of load changes and determine load limits of the voltage regulator.

APPARATUS: -

Zener diode. Regulated Power Supply (0-30V). Voltmeter (0-20V) Ammeter (0-100mA) Resistor (1KOhm) Bread Board Connecting wires

CIRCUIT DIAGRAM:-

STATIC CHARACTERISTICS:-


REGULATION CHARACTERISTICS :-

Theory:-

A zener diode is heavily doped p-n junction diode, specially made to operate in the break down

region. A p-n junction diode normally does not conduct when reverse biased. But if the reverse

bias is increased, at a particular voltage it starts conducting heavily. This voltage is called Break

down Voltage. High current through the diode can permanently damage the device

To avoid high current, we connect a resistor in series with zener diode. Once the diode starts

conducting it maintains almost constant voltage across the terminals whatever may be the

current through it, i.e., it has very low dynamic resistance. It is used in voltage regulators.

PROCEDURE:-

Static characteristics:-


2. The Regulated power supply voltage is increased in steps.

3. The zener current (lz), and the zener voltage (Vz) are observed and then noted in the tabular

form.

4. A graph is plotted between zener current (Iz) and zener voltage (Vz).

Regulation characteristics:-


1. The voltage regulation of any device is usually expressed as percentage regulation

2. The percentage regulation is given by the formula

((VNL-VFL)/VFL)X100

VNL=Voltage across the diode, when no load is connected.

VFL=Voltage across the diode, when load is connected.

3. Connection are made as per the circuit diagram

4. The load is placed in full load condition and the zener voltage (V z), Zener current (lz), load

current (IL) are measured.

5. The above step is repeated by decreasing the value of the load in steps.

6. All the readings are tabulated.

7. The percentage regulation is calculated using the above formula

OBSERVATIONS:-

Static characteristics:-

S.NO ZENER

VOLTAGE(VZ)

ZENER CURRENT(IZ)


Regulation characteristics:-

S.N0

VNL(VOLTS) VFL

(VOLTS)RL

(KΏ)% REGULATION

MODEL WAVEFORMS:-

PRECAUTIONS:-

1. The terminals of the zener diode should be properly identified

2. While determined the load regulation, load should not be immediately shorted.


3. Should be ensured that the applied voltages & currents do not exceed the ratings of the

diode.

RESULT:-

a) Static characteristics of zener diode are obtained and drawn.

b) Percentage regulation of zener diode is calculated.

VIVAQUESTIONS:-

1. What type of temp? Coefficient does the zener diode have?

2. If the impurity concentration is increased, how the depletion width effected?

3. Does the dynamic impendence of a zener diode vary?

4. Explain briefly about avalanche and zener breakdowns?

5. Draw the zener equivalent circuit?

6. Differentiate between line regulation & load regulation?

7. In which region zener diode can be used as a regulator?

8. How the breakdown voltage of a particular diode can be controlled?

9. What type of temperature coefficient does the Avalanche breakdown has?

10. By what type of charge carriers the current flows in zener and avalanche breakdown diodes?


3. SINGLE STAGE AMPLIFIER

AIM : 1. Plot frequency response curve for single stage amplifier and to determine gain bandwidth product.

APPRATUS :

N-channel FET (BFW11)Resistors (6.8KΩ, 1MΩ, 1.5KΩ)Capacitors (0.1µF, 47µF)Regulated power Supply (0-30V)Function generatorCROCRO probesBread boardConnecting wires

CIRCUIT DIAGRAM:


THEORY:

A field-effect transistor (FET) is a type of transistor commonly used for weak-signal

amplification (for example, for amplifying wireless (signals). The device can amplify analog or

digital signals. It can also switch DC or function as an oscillator. In the FET, current flows along

a semiconductor path called the channel. At one end of the channel, there is an electrode called

the source. At the other end of the channel, there is an electrode called the drain. The physical

diameter of the channel is fixed, but its effective electrical diameter can be varied by the

application of a voltage to a control electrode called the gate. Field-effect transistors exist in two

major classifications. These are known as the junction FET (JFET) and the metal-oxide-

semiconductor FET (MOSFET). The junction FET has a channel consisting of N-type

semiconductor (N-channel) or P-type semiconductor (P-channel) material; the gate is made of

the opposite semiconductor type. In P-type material, electric charges are carried mainly in the

form of electron deficiencies called holes. In N-type material, the charge carriers are primarily

electrons. In a JFET, the junction is the boundary between the channel and the gate. Normally,

this P-N junction is reverse-biased (a DC voltage is applied to it) so that no current flows

between the channel and the gate. However, under some conditions there is a small current

through the junction during part of the input signal cycle. The FET has some advantages and

some disadvantages relative to the bipolar transistor. Field-effect transistors are preferred for

weak-signal work, for example in wireless, communications and broadcast receivers. They are

also preferred in circuits and systems requiring high impedance. The FET is not, in general, used

for high-power amplification, such as is required in large wireless communications and

broadcast transmitters.

Field-effect transistors are fabricated onto silicon integrated circuit (IC) chips. A single IC can

contain many thousands of FETs, along with other components such as resistors, capacitors, and

diodes.

PROCEDURE:


2. A signal of 1 KHz frequency and 50mV peak-to-peak is applied at the

Input of amplifier.


3. Output is taken at drain and gain is calculated by using the expression,

Av=V0/Vi

4. Voltage gain in dB is calculated by using the expression,

Av=20log 10(V0/Vi)

5. Repeat the above steps for various input voltages.

6. Plot Av vs. Frequency

7. The Bandwidth of the amplifier is calculated from the graph using the

Expression,

Bandwidth BW=f2-f1

Where f1 is lower 3 dB frequency

f2 is upper 3 dB frequency

OBSERVATIONS:

S.NO INPUT

VOLTAGE(Vi)

OUTPUT

VOLTAGE(V0)

VOLTAGE GAIN

Av= (V0/Vi)


MODEL GRAPH:

PRECAUTIONS:

1. All the connections should be tight.

2. Transistor terminals must be identified properly

RESULT: The frequency response of the common source FET Amplifier and Bandwidth is

obtained.


VIVA QUESTIONS

1. What is the difference between FET and BJT?

2. FET is unipolar or bipolar?

3. Draw the symbol of FET?

4. What are the applications of FET?

5. FET is voltage controlled or current controlled?

6. Draw the equivalent circuit of common source FET amplifier?

7. What is the voltage gain of the FET amplifier?

8. What is the input impedance of FET amplifier?

9. What is the output impedance of FET amplifier?

10. What are the FET parameters?

11. What are the FET applications?


4. FET CHARACTERISTICS

AIM: Plot drain current - drain voltage and drain current – gate bias characteristics of field effect transistor and measure of Idss & Vp.

APPARATUS: FET (BFW-11)

Regulated power supply Voltmeter (0-20V) Ammeter (0-100mA) Bread board Connecting wires

THEORY:

A FET is a three terminal device, having the characteristics of high input impedance and less

noise, the Gate to Source junction of the FET s always reverse biased. In response to small

applied voltage from drain to source, the n-type bar acts as sample resistor, and the drain current

increases linearly with VDS. With increase in ID the ohmic voltage drop between the source and

the channel region reverse biases the junction and the conducting position of the channel begins

to remain constant. The VDS at this instant is called “pinch of voltage”.

If the gate to source voltage (VGS) is applied in the direction to provide additional reverse bias,

the pinch off voltage ill is decreased. In amplifier application, the FET is always used in the

region beyond the pinch-off.

FDS=IDSS(1-VGS/VP)^2


CIRCUIT DIAGRAM

PROCEDURE:

1. All the connections are made as per the circuit diagram.

2. To plot the drain characteristics, keep VGS constant at 0V.

3. Vary the VDD and observe the values of VDS and ID.

4. Repeat the above steps 2, 3 for different values of VGS at 0.1V and 0.2V.

5. All the readings are tabulated.

6. To plot the transfer characteristics, keep VDS constant at 1V.

7. Vary VGG and observe the values of VGS and ID.

8. Repeat steps 6 and 7 for different values of VDS at 1.5 V and 2V.

9. The readings are tabulated.

10. From drain characteristics, calculate the values of dynamic resistance (rd) by using the

formula

rd = ∆VDS/∆ID

11. From transfer characteristics, calculate the value of transconductace (gm) By using the

formula

Gm=∆ID/∆VDS

12. Amplification factor (μ) = dynamic resistance. Tran conductance

μ = ∆VDS/∆VGS


OBSERVATIONS :

DRAIN CHARACTERISTICS:

S.NO VGS=0V VGS=0.1V VGS=0.2V

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

TRANSFER CHARACTERISTICS :

S.NO VDS

=0.5V

VDS=1V VDS =1.5V

VGS (V) ID(mA) VGS (V) ID(mA) VGS (V) ID(mA)


MODEL GRAPH:

TRANSFER CHARACTERISTICS

DRAIN CHARACTERISTICS


PRECAUTIONS:

1. The three terminals of the FET must be carefully identified

2. Practically FET contains four terminals, which are called source, drain, Gate, substrate.

3. Source and case should be short circuited.

4. Voltages exceeding the ratings of the FET should not be applied.

RESULT:

1. The drain and transfer characteristics of a given FET are drawn

2. The dynamic resistance (rd), amplification factor (μ) and Tran conductance (gm) of the

given FET are calculated.

VIVA QUESTIONS:

1. What are the advantages of FET?

2. Different between FET and BJT?

3. Explain different regions of V-I characteristics of FET?

4. What are the applications of FET?

5. What are the types of FET?

6. Draw the symbol of FET.

7. What are the disadvantages of FET?

8. What are the parameters of FET?


6. CLIPPING AND CLAMPING CIRCUITS

AIM : Application of Diode as clipper & clamper.

APPARATUS :

Diode (IN914 / IN4007) Resistors-1 K& 100k DC Regulated power supply (for Vref) Signal generator (for Vi) CRO

THEORY:

CIRCUIT DIAGRAM OF POSITIVE CLIPPER

Fig.1 a. Positive clipper Circuit b. Transfer Characteristics

Clippers clip off a portion of the input signal without distorting the remaining part of the

waveform. In the positive clipper shown above the input waveform above Vref is clipped off.

If Vref = 0V, the entire positive half of the input waveform is clipped off. Plot of input Vi

(along X-axis) versus output Vo (along Y-axis) called transfer characteristics of the circuit

can also be used to study the working of the clippers.

For stiff clipper: 100RB < RS< 0.01RL, Where RB is bulk resistance of the diode. For diode

IN914, value of RB is 30Ω.Series resistor RS must be 100times greater than bulk resistance RB

and 100 times smaller than load resistance RL. If RB=30 Ω, select RS=1k Ω and RL=100kΩ.


PROCEDURE:

1. Before making the connections check all components using multimeter.

2. Make the connections as shown in circuit diagram.

3. Using a signal generator (Vi) apply a sine wave of 1KHz frequency and a peak-to peak

amplitude of 10V to the circuit. (Square wave can also be applied.)

4. Keep the CRO in dual mode; connect the input (Vi) signal to channel 1 and output

waveform (Vo) to channel 2. Observe the clipped output waveform which is as shown in fig.

2. Also record the amplitude and time data from the waveforms.

5. Now keep the CRO in X-Y mode and observe the transfer characteristic waveform

Note:

1. Vary Vref and observe the variation in clipping level. For this use variable DC power supply

for Vref.

2. Change the direction of diode and Vref to realize a negative clipper.

3. For double-ended clipping circuit, make the circuit connections as shown in fig.3 and the

output waveform observed is as shown in figure 5.

4. Adjust the ground level of the CRO on both channels properly and view the output in DC

mode (not in AC mode) for both clippers and clampers.

WAVEFORMS

Fig. 2. Input and output waveform for positive Clipper


RESULT:

Output voltage V0 =__________ during positive half cycle

=__________ during negative half cycle

DOUBLE ENDED CLIPPER

CIRCUIT DIAGRAM

Fig.3 a. Double ended clipper Circuit b. Transfer Characteristics

Apply Vi = 10 Vpp at 1kHz

V1= 2VV2= -2V

WAVE FORMS

Fig.4. Input and output waveform for double-ended clipping circuit


RESULT:

Output voltage V0 =__________ during positive half cycle

=__________ during negative half cycle

Note:

The above clipper circuits are realized using the diodes in parallel with the load (at the

output), hence they are called shunt clippers. The positive (and negative) clippers can also be

realized in the series configuration wherein the diode is in series with the load. These circuits

are called series clippers.

POSITIVE CLAMPER

COMPONENTS REQUIRED :

Diode (IN 914/BY-127) Resistor of 100 K Capacitor - 1F DC regulated power supply Signal generator CRO

CIRCUIT DIAGRAM

Fig. 5 Positive Clamper

The clamping network is one that will “clamp” a signal to a different DC level. The network

must have a capacitor, a diode and a resistive element, but it can also employ an independent

DC supply (Vref) to introduce an additional shift. The magnitude of R and C must be chosen

such that time constant τ = RLC is large enough to ensure the voltage across capacitor does

not discharge significantly during the interval of the diode is non-conducting


DESIGN:

For proper clamping, τ >100T where T is the time period of input waveform

If frequency is 1 kHz with peak-peak input voltage of 10V, T=1ms

τ = RL.C=100×T = 100ms

Let C=1μF

RL= 100×10-3 =100kΩ

1×10-6

Select C =1uF and RL =100 kΩ

PROCEDURE:

1. Before making the connections check all components using multimeter.

2. Make the connections as shown in circuit diagram (fig. 5).

3. Using a signal generator apply a square wave input (Vi) of peak-to-peak amplitude of 10V

(and frequency greater than 50Hz) to the circuit (Sine wave can also be applied).

4. Observe the clamped output waveform on CRO which is as shown in Fig. 6.

Note:

1. For clamping circuit with reference voltage Vref, the output waveform is observed as

shown in Fig. 7. For without reference voltage, Keep Vref = 0V.

2. CRO in DUAL mode and DC mode. Also the grounds of both the channels can be made to

have the same level so that the shift in DC level of the output can be observed.

3. For negative clampers reverse the directions of both diode and reference voltage.

Fig. 6 Input and output waveform for positive clamper without reference voltage.


Fig. 7 Input and output waveform for positive clamper circuit with reference voltage = 2V

RESULT:

With Vref =0, output voltage V0=_________With Vref =2, output voltage V0=________

VIVA QUESTIONS

1) Explain difference between clipper and clamper.2) Explain positive and negative clipper level?3) What is the basic difference between clipper and clamper and voltage multiplier?4) What are the applications of clipper and clamper?


6. RC COUPLED AMPLIFIER

AIM: Plot gain- frequency characteristic of two stages RC coupled amplifier & calculate its bandwidth and compare it with theoretical value.

APPARATUS:

Transistors - BC 107 -2Nos,Resistors - 3.3K -2Nos,

33k -2Nos, 330Ω -2Nos, 1k -2Nos,

Capacitors - 100uF -3Nos, 10uF -2Nos, Bread Board,

Regulated power supply,Cathode ray oscilloscope,

THEORY:

This is most popular type of coupling as it provides excellent audio fidelity.

A coupling capacitor is used to connect output of first stage to input of second stage.

Resistances R1, R2, Re form biasing and stabilization network. Emitter bypass capacitor

offers low reactance paths to signal coupling Capacitor transmits ac signal, blocks DC.

Cascade stages amplify signal and overall gain is increased total gain is less than product

of gains of individual stages. Thus for more gain coupling is done and overall gain of

two stages equals to A=A1*A2

A1=voltage gain of first stage

A2=voltage gain of second stage.

When ac signal is applied to the base of the transistor, its amplified output appears

across the collector resistor Rc. It is given to the second stage for further amplification

and signal appears with more strength. Frequency response curve is obtained by plotting

a graph between frequency and gain in db .The gain is constant in mid frequency range

and gain decreases on both sides of the mid frequency range. The gain decreases in the

low frequency range due to coupling capacitor Cc and at high frequencies due to

junction capacitance Cbe.


CIRCUIT DIAGRAM:

PROCEDURE:

1. Apply input by using function generator to the circuit.

2. Observe the output waveform on CRO.

3. Measure the voltage at

a. Output of first stage

b. Output of second stage.

4. From the readings calculate voltage gain of first stage, second stage and overall

gain of two stages. Disconnect second stage and then measure output voltage of

first stage calculates voltage gain.

5. Compare it with voltage gain obtained when second stage was connected.

6. Note down various values of gain for different frequencies.

7. A graph is plotted between frequency and voltage gain.


OBSERVATIONS: -

APPLIED

FREQUENCY

O/P VOLTAGE

(Vo)

VOLTAGE GAIN

in dB (20 log10Vo/Vi)

MODELGRAPH:-

INPUT WAVE FORM:

FIRST STAGE OUTPUT:

SECOND STAGE OUTPUT:


FREQUENCY RESPONSE:

PRECAUTIONS:

1) All connections should be tight.

2) Transistor terminals must be identifying properly.

3) Reading should be taken without any parallax error.

RESULT: Thus voltage gain is calculated and frequency response is observed along

with loading affect.

VIVA QUESTIONS:

1) What is the necessity of cascading?

2) What is 3dB bandwidth?

3) Why RC coupling is preferred in audio range?

4) Which type of coupling is preferred and why?

5) Explain various types of Capacitors?

6) What is loading effect?

7) Why it is known as RC coupling?

8) What is the purpose of emitter bypass capacitor?

9) Which type of biasing is used in RC coupled amplifier?


8. COMMON EMITTER FOLLOWER

AIM: Plot gain- frequency characteristic of emitter follower & find out its input and output resistances.

APPARATUS: FETBFW10Transistor BC107ResistorsCapacitorsCROFunction GeneratorMulti meter

THEORY:

CIRCUITDIAGRAM:


The common collector circuit is also known as emitter follower. The ac output voltage from a

CC circuit is essentially the same as the input voltage; there is no voltage gain or phase shift.

Thus, the CC circuit can be said to have a voltage gain of 1. The fact that the CC output

voltage follows the changes in signal voltage gives the circuit its other name emitter follower.

The input impedance of a CC amplifier is high. Output impedance is low and the Voltage

gain is almost unity. Because of these Characteristics the CC circuit is normally used as a

buffer amplifier, placed between a high impedance signal source and a low impedance load.

SOURCE FOLLOWER

The FET common drain circuit has the output voltage developed across the source resistor R s.

Here the ac output voltage is closely equal to the ac input voltage, and the circuit can be said

to have unity gain. Because the output voltage at the source terminal follows the signal

voltage at the gate, the common drain circuit is also known as a source follower. A common

drain circuit has a voltage gain approximately equal to 1, no phase shift between input and

output, very high input impedance and low output impedance. Because of its high Z i, low Zo

and unity gain the CD circuit is used as a buffer amplifier between a high impedance signal

source and a low impedance load.


PROCEDURE:

1. Connect the circuit as per the circuit diagram.

2. Apply Vslv 1 KHz signal from the signal generator.

3. Observe corresponding output from the CRO and then calculate voltage gain using the

formula Av=Vo/Vi.

4. Measure voltage across AB terminals and then calculate input current by using the formula

Iin=Vab/Rab.

5. Measure current flowing through resistor at Source (or Emitter) terminal and note down it

as Iout.

6. Calculate Current gain using the formula AI=Iin/Iout.

7. Calculate input resistance using the formula Rin=Vin/Iin.

8. To calculate the output resistance, connect the pot at the output and vary the resistance of

the pot up to half of the output with RL is equal to infinity. The resistance of pot is the output

resistance.

OBSERVATIONS:

Frequency(Hz) Voltage gain (V) Current gain(mA)


MODELWAVEFORM:

PRECAUTIONS:

1. Wires should be checked for good continuity

2. FET terminals must be identified and connected carefully.

RESULT: Gain- frequency characteristic of emitter follower is successfully plotted & its input and output resistances also calculated.


9(a). TRANSISTOR CB CHARACTERSTICS

AIM: 1.To observe and draw the input and output characteristics of a transistor

connected in common base configuration.

2. To find α of the given transistor.

APPARATUS: Transistor, BC 107 Regulated power supply (0-30V, 1A) Voltmeter (0-20V) Ammeters (0-100mA) Resistor, 1000Ω Bread board Connecting wiresTHEORY:

A transistor is a three terminal active device. T he terminals are emitter, base, collector. In CB

configuration, the base is common to both input (emitter) and output (collector). For normal

operation, the E-B junction is forward biased and C-B junction is reverse biased.

In CB configuration, IE is positive, IC is negative and IB is negative. So,

VEB=f1 (VCB,IE) and

IC=f2 (VCB,IB)

With an increasing the reverse collector voltage, the space-charge width at the output junction

increases and the effective base width ‘W’ decreases. This phenomenon is known as “Early

effect”. Then, there will be less chance for recombination within the base region. With increase of

charge gradient with in the base region, the current of minority carriers injected across the emitter

junction increases. The current amplification factor of CB configuration is given by,

α= ∆IC/ ∆IE

CIRCUIT DIAGRAM


PROCEDURE:

INPUT CHARACTERISTICS:


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

different values of VEB note down the values of IE.

3. Repeat the above step keeping VCB at 2V, 4V, and 6V.All the readings is tabulated.

4. A graph is drawn between VEB and IE for constant VCB.

OUTPUT CHARACTERISTICS:


2. For plotting the output characteristics, the input IE iskept constant at 10m A and for different

values of VCB, note down the values of IC.

3. Repeat the above step for the values of IE at 20 mA, 40 mA, and 60 mA, all the readings

are tabulated.

4. A graph is drawn between VCB and Ic for constant IE

OBSERVATIONS:



S.No VCB=0V VCB=1V VCB=2V

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


S.No

IE=10mA IE=20mA IE=30mA

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


MODEL GRAPHS:

INPUT CHARACTERISTICS

OUTPUT CHARACTERISTICS


PRECAUTIONS:

1. The supply voltages should not exceed the rating of the transistor.

2. Meters should be connected properly according to their polarities.

RESULT:

1. The input and output characteristics of the transistor are drawn.

2. The α of the given transistor is calculated.

VIVA QUESTIONS:

1. What is the range of α for the transistor?

2. Draw the input and output characteristics of the transistor in CB configuration?

3. Identify various regions in output characteristics?

4. What is the relation between α and β?

5. What are the applications of CB configuration?

6. What are the input and output impedances of CB configuration?

7. Define α (alpha)?

8. What is EARLY effect?

9. Draw diagram of CB configuration for PNP transistor?

10. What is the power gain of CB configuration?


9(b). TRANSISTOR CC CHARACTERSTICS

AIM: To study the input and output characteristics of a transistor in common collector

configuration and to determine its h parameters.

APPARATUS:

Transistor BC147 1

Resistance 68 k, 1k ohm 1

Regulated power supply (0 – 30V) 2

Ammeter (1-10)mA, (0-500)µA 1

Voltmeter (0 – 1) V, (0 – 30) V 1

Bread board

Connecting wires

THEORY:

Bipolar junction transistor (BJT) is a three terminal (emitter, base, collector) semiconductor

device. There are two types of transistors namely NPN and PNP. It consists of two P-N

junctions namely emitter junction and collector junction. In Common collector configuration the

input is applied between base and collector terminals and the output is taken from collector and

emitter. Here collector is common to both input and output and hence the name common

collector configuration. Input characteristics are obtained between the input current and input

voltage taking output voltage as parameter. It is plotted between VBC and IB at constant VCE in CC

configuration. Output characteristics are obtained between the output voltage and output current

taking input current as parameter. It is plotted between VCE and IE at constant IB in CC

configuration.


CIRCUIT DIAGRAM:

PROCEDURE:

INPUT CHARECTERSTICS:

1. Connect the transistor in CC configuration as per circuit diagram.

2. Keep output voltage VCE = 0V by varying VEE.

3. Varying VBB gradually, note down both base current IB and base collector voltage (VBC).

4. Repeat above procedure (step 3) for various values of VC (VBC).

OUTPUT CHARACTERSTICS:

1. Make the connections as per circuit diagram.

2. By varying VBB keep the base current IB = 20µA.

3. Varying VCC gradually, note down the readings of emitter-current (IE) and collector- Emitter

voltage (VCE).

4. Repeat above procedure (step 3) for different values of IE .


OBSERVATIONS:


S.NOVCB = 1V VCB = 2V VCB = 4V

VEB(V) IE(μA) VEB(V) IE(μA) VEB(V) IE(μA)

OUT PUT CHAREACTARISTICS:

S.NOIB = 50 μA IB = 75 μA IB = 100 μA

VCE(V) IE(mA) VCE(V) IEmA) VCE(V) IE(mA)

MODEL GRAPHS:

INPUT CHARACTERSTICS:


OUTPUT CHARECTERSTICS:

Calculations from graph:

a) Input impedance (hic) = ∆VBC / ∆IB

(b) Forward current gain (hfc) = ∆IE / ∆IB

(c) Output admittance (hoc) = ∆IE / ∆ VEC

(d) Reverse voltage gain (hrc) = ∆VBC/∆ VEC

RESULT:

Thus the input and output characteristics of CC configuration are plotted and h parameters are

found.

a) Input impedance (hic) =

b) Forward current gain (hfc) =

c) Output admittance (hoc) =

d) Reverse voltage gain (hrc) =


PRECAUTIONS:

1. The supply voltage should not exceed the rating of the transistor

2. Meters should be connected properly according to their polarities

VIVA QUESTIONS:

1. What are the applications of CC configuration?

2. Compare the voltage gain and input and output impedances of CE and CC configurations.

3. BJT is a current controlled device. Justify

4. Why CC Configuration is called emitter follower?

5. Can we use CC configuration as an amplifier?

6. What is the need for analyzing the transistor circuits using different parameters?

7. What is the significance of hybrid model of a transistor?

8. Is there any phase shift between input and output in CC configuration?


9(c). TRANSISTOR CE CHARACTERSTICS

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

2. To find β of the given transistor.

APPARATUS:

Transistor (BC 107) R.P.S (O-30V) 2Nos Voltmeters (0-20V) 2Nos Ammeters (0-200μA) & (0-500mA) Resistors 1Kohm Bread board

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. As

compared to CB arrangement IB increases less rapidly with VBE. Therefore input resistance of CE

circuit is higher than that of CB circuit.

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

with VCE unto 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 = ΔIC/ΔIB


CIRCUIT DIAGRAM:

PROCEDURE:

INPUT CHARECTERSTICS:

1. Connect the circuit as per the circuit diagram.

2. For plotting the input characteristics the output voltage VCE is kept constant at 1V and for

different values of VBE. Note down the values of IC

3. Repeat the above step by keeping VCE at 2V and 4V.

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 10μA 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 the all the readings

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


OBSERVATIONS:


S.NOVCE = 1V VCE = 2V VCE = 4V

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

OUT PUT CHAREACTARISTICS:

S.NOIB = 50 μA IB = 75 μA IB = 100 μA

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


MODEL GRAPHS:

INPUT CHARACTERSTICS:

OUTPUT CHARECTERSTICS:


PRECAUTIONS:

1. The supply voltage should not exceed the rating of the transistor

2. Meters should be connected properly according to their polarities

RESULT:

1. the input and output characteristics of a transistor in CE configuration are Drawn

2. the of a given transistor is calculated

VIVA QUESTIONS:

1. What is the range of for the transistor?

2. What are the input and output impedances of CE configuration?

3. Identify various regions in the output characteristics?

4. what is the relation between

5. Define current gain in CE configuration?

6. Why CE configuration is preferred for amplification?

7. What is the phase relation between input and output?

8. Draw diagram of CE configuration for PNP transistor?

9. What is the power gain of CE configuration?

10. What are the applications of CE configuration?


h-PARAMETERS OF CE CONFIGURATION

AIM: To calculate the H-parameters of transistor in CE configuration.

APPRATUS: Transistor BC 107Resistors 100 K Ώ 100 Ώ Ammeter (0-200µA), (0-200mA)Voltmeter (0-20V) - 2NosRegulated Power Supply (0-30V, 1A) - 2NosBreadboard

THEORY:


The two sets of characteristics are necessary to describe the behavior of the CE configuration

one for input or base emitter circuit and other for the output or collector emitter circuit.

In input characteristics the emitter base junction forward biased by a very small voltage VBB

where as collector base junction reverse biased by a very large voltage VCC. The input

characteristics are a plot of input current IB Vs the input voltage VBE for a range of values of

output voltage VCE. The following important points can be observed from these characteristics

curves.

1. The characteristics resemble that of CE configuration.

2. Input resistance is high as IB increases less rapidly with VBE

3. The input resistance of the transistor is the ratio of change in base emitter voltage ΔV BE to

change in base current ΔIB at constant collector emitter voltage (VCE) i.e. Input resistance or

input impedance hie = ΔVBE / ΔIB at VCE constant.


A set of output characteristics or collector characteristics are a plot of out put current I C VS

output voltage VCE for a range of values of input current IB .The following important points can

be observed from these characteristics curves:-

1. The transistor always operates in the active region. I.e. the collector current


IC increases with VCE very slowly. For low values of the VCE the IC increases rapidly with a small

increase in VCE .The transistor is said to be working in saturation region.

Output resistance is the ratio of change of collector emitter voltage ΔVCE , to change in collector

current ΔIC with constant IB. Output resistance or Output impedance hoe = ΔVCE / ΔIC at IB

constant.

Input Impedance hie = ΔVBE / ΔIB at VCE constant

Output impedance hoe = ΔVCE / ΔIC at IB constant

Reverse Transfer Voltage Gain hre = ΔVBE / ΔVCE at IB constant

Forward Transfer Current Gain hfe = ΔIC / ΔIB at constant VCE

CIRCUIT DIAGRAM:


PROCEDURE:

1. Connect a transistor in CE configuration circuit for plotting its input and output

characteristics.

2. Take a set of readings for the variations in IB with VBE at different fixed values of output

voltage VCE.

3. Plot the input characteristics of CE configuration from the above readings.

4. From the graph calculate the input resistance hie and reverse transfer ratio hre by taking the

slopes of the curves.

5. Take the family of readings for the variations of IC with VCE at different values of fixed IB.

6. Plot the output characteristics from the above readings.

7. From the graphs calculate hfe ands hoe by taking the slope of the curves.

Tabular Forms

Input Characteristics

S.NOVCE=0V VCE=6V

VBE(V) IB(μA) VBE(V) IB(μA)

Output Characteristics

S.NOIB = 20 µA IB = 40 µA IB = 60 µA

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


MODEL WAVEFORM: Input Characteristics


Output Characteristics


RESULT: The H-Parameters for a transistor in CE configuration are calculated from the input

and output characteristics.

1. Input Impedance hie =

2. Reverse Transfer Voltage Gain hre =

3. Forward Transfer Current Gain hfe =

4. Output conductance hoe =

VIVA QUESTIONS:

1. What are the h-parameters?

2. What are the limitations of h-parameters?

3. What are its applications?

4. Draw the Equivalent circuit diagram of H parameters?


5. Define H parameter?

6. What are tabular forms of H parameters monoculture of a transistor?

7. What is the general formula for input impedance?

8. What is the general formula for Current Gain?

9. What is the general formula for Voltage gain?


10. HALF – WAVE RECTIFIER

AIM: - Study half wave rectifier and effect of filters on wave. Also calculate theoretical & practical ripple factor.

APPARATUS:- Experimental Board Multimeters 2No’s. Transformer (6-0-6). Diode, 1N 4007 Capacitor 100μf. Resistor 1KΩ. Connecting wires THEORY: -

During positive half-cycle of the input voltage, the diode D1 is in forward bias and conducts

through the load resistor R1. Hence the current produces an output voltage across the load resistor

R1, which has the same shape as the positive half cycle of the input voltage.

During the negative half-cycle of the input voltage, the diode is reverse biased and there is no

current through the circuit. i.e, the voltage across R1 is zero. The net result is that only the

positive half cycle of the input voltage appears across the load. The average value of the half

wave rectified o/p voltage is the value measured on dc voltmeter.

For practical circuits, transformer coupling is usually provided for two reasons.

1. The voltage can be stepped-up or stepped-down, as needed.

2. The ac source is electrically isolated from the rectifier. Thus preventing shock hazards in the

secondary circuit.


CIRCUIT DIAGRAM:-

PROCEDURE:-


2. Connect the primary side of the transformer to ac mains and the secondary side to the rectifier

input.

3. By the multimeter, measure the ac input voltage of the rectifier and, ac and dc voltage at the

output of the rectifier.

4. Find the theoretical of dc voltage by using the formula,

Vdc=Vm/П

Where, Vm=2Vrms, (Vrms=output ac voltage.)

The Ripple factor is calculated by using the formula

r=ac output voltage/dc output voltage.


REGULATION CHARACTERSTICS:-


2. By increasing the value of the rheostat, the voltage across the load and current flowing

through the load are measured.

3. The reading is tabulated.

4. Draw a graph between load voltage (VL and load current ( IL ) taking VL on X-axis and

IL on y-axis

5. From the value of no-load voltages, the %regulation is calculated using the formula,

Theoretical calculations for Ripple factor:-

Without Filter :-

Vrms=Vm/2

Vm=2Vrms

Vdc=Vm/П

Ripple factor r=√ (Vrms/ Vdc )2 -1 =1.21

With Filter:-

Ripple factor, r=1/ (2√3 f C R)

Where f =50Hz

C =100µF

RL=1KΩ

PRACTICAL CALCULATIONS:-

Vac=

Vdc=

Ripple factor without Filter =

Ripple factor with Filter =


OBSERVATIONS:-

WITHOUT FILTER

USING

DMM

Vac(v) Vdc(v) r= Vac/ Vdc

WITH FILTER

USING

DMM


WITHOUTFILTER:-

Vdc=Vm/П, Vrms=Vm/2, Vac=√ ( Vrms2- Vdc 2)

USING

CRO

Vm(v) Vac(v) Vdc(v) r= Vac/ Vdc

WITHFILTER

USINGCRO

V1(V) V2(V) Vdc=

(V1+V2)/2

Vac=

(V1- V2)/2√3

r=

Vac/ Vdc


PRECAUTIONS:

1. The primary and secondary sides of the transformer should be carefully identified.

2. The polarities of the diode should be carefully identified.

3. While determining the % regulation, first Full load should be applied and then it

should be decremented in steps.

RESULT :-

1. The Ripple factor for the Half-Wave Rectifier with and without filters is measured.

2. The % regulation of the Half-Wave rectifier is calculated.

VIVA QUESTIONS:

1. What is the PIV of Half wave rectifier?

2. What is the efficiency of half wave rectifier?

3. What is the rectifier?

4. What is the difference between the half wave rectifier and full wave Rectifier?

5. What is the o/p frequency of Bridge Rectifier?

6. What are the ripples?

7. What is the function of the filters?

8. What is TUF?

9. What is the average value of o/p voltage for HWR?

10. What is the peak factor?


11. BRIDGE RECTIFER

AIM: - Study bridge rectifier and measure the effect of filter network on D.C. voltage output & ripple.

APPARATUS:-

Experimental board Diodes IN4007 4 Nos. Resistor 1KΩ Capacitor 100μF/25v. Transformer (6-0-6V) Multi meters 2 Nos. Connecting Wires

CIRCUIT DIAGRAM:-

THEORY:-

The bridge rectifier is also a full-wave rectifier in which four p-n diodes are connected in the

form of a bridge fashion. The Bridge rectifier has high efficiency when compared to half-wave

rectifier. During every half cycle of the input, only two diodes will be conducting while other

two diodes are in reverse bias.

PROCEDURE:-



2. Connect the ac main to the primary side of the transformer and secondary side to the bridge

rectifier.

3. Measure the ac voltage at the input of the rectifier using the multi meter.

4. Measure both the ac and dc voltages at the output of the Bridge rectifier.

5. Find the theoretical value of dc voltage by using the formula,

CALCULATIONS:-

Theoretical calculations:-

Vrms = Vm/ √2

Vm =Vrms√2

Vdc=2Vm/П

(i)Without filter:

Ripple factor, r = √ ( Vrms/ Vdc )2 -1 = 0.482

(ii)With filter:

Ripple factor, r = 1/ (4√3 f C RL) where f =50Hz

C =100µF

RL=1KΩ

Practical Calculations:-

Without filter:-

Vac=

Vdc=

Ripple factor, r=Vac/Vdc

With filters:-

Vac=


Vdc=

Ripple factor, r=Vac/Vdc

OBSEVATIONS:-

Without Filter

USING

DMM


With Filter

USING

DMM


Without Filter:-

Vrms = Vm/ √2 , Vdc=2Vm/П , Vac=√( Vrms2- Vdc

2)

USING CRO


WITH FILTER

USINGCRO

V1(V) V2(V) Vdc=

(V1+V2)/2

Vac=

(V1- V2)/2√3

r=

Vac/

Vdc


MODELWAVEFORM:-

PRECAUTIONS:-

1. The voltage applied should not exceed in the ratings of the diode

2. The diodes will be connected correctly

RESULT:-

The Ripple factor of Bridge rectifier is with and without filter calculated.


VIVAQUESTIONS:-

1. What is the PIV of Bridge rectifier?

2. What is the efficiency of Bridge rectifier?

3. What are the advantages of Bridge rectifier?

4. What is the difference between the Bridge rectifier and full wave rectifier?

5. What is the o/p frequency of Bridge Rectifier?

6. What is the disadvantage of Bridge Rectifier?

7. What is the maximum secondary voltage of a transformer?

8. What are the different types of the filters?

9. What is the difference between the Bridge rectifier and half wave Rectifier?

10. What is the maximum DC power delivered to the load?


Department of Electronics & Communication

Beyond The Syllabus

3EC9 ELECTRONICS LAB-I

(ELECTRONICS & COMMUNICATION)

S. No. List of Experiments Beyond The Syllabus Page

No.

1 To find the Ripple factor and regulation of a Full-wave Rectifier

with and without filter.

2 To observe the characteristics of UJT and to calculate the

Intrinsic Stand-Off Ratio (η).

3 To draw the V-I Characteristics of SCR


1. FULL-WAVE RECTIFIER

AIM:-To find the Ripple factor and regulation of a Full-wave Rectifier with and without filter.

APPARATUS:-

Experimental Board

Transformer (6-0-6V).

P-n Diodes, (lN4007) ---2 No’s

Multimeters –2No’s

Filter Capacitor (100μF/25V) -

Connecting Wires

Load resistor, 1KΩ

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).


CIRCUIT DIAGRAM:-

PROCEDURE:


3. Connect the ac mains to the primary side of the transformer and the secondary side to the

rectifier.

4. Measure the ac voltage at the input side of the rectifier.

5. Measure both ac and dc voltages at the output side the rectifier.

6. Find the theoretical value of the dc voltage by using the formula Vdc=2Vm/П

7. Connect the filter capacitor across the load resistor and measure the values of V ac and Vdc

at the output.

8. The theoretical values of Ripple factors with and without capacitor are calculated.

9. From the values of Vac and Vdc practical values of Ripple factors are calculated. The

practical values are compared with theoretical values.


THEORITICAL CALCULATIONS:-

Vrms = Vm/ √2

Vm =Vrms√2

Vdc=2Vm/П

(i)Without filter:

Ripple factor, r = √ ( Vrms/ Vdc )2 -1 = 0.482

(ii)With filter:

Ripple factor, r = 1/ (4√3 f C RL) where f =50Hz

C =100µF

RL=1KΩ

PRACTICAL CALCULATIONS:

Without filter:-

Vac=

Vdc=

Ripple factor, r= Vac/Vdc

With filters:-

Vac=

Vdc=

Ripple factor=Vac/Vdc


Without Filter:

USING

DMM


With Filter

USING

DMM


Without Filter

Vrms = Vm/ √2 , Vdc=2Vm/П , Vac=√( Vrms2- Vdc 2)

USING

CRO


With Filter

USINGCRO

V1(V) V2(V) Vdc=

(V1+V2)/2

Vac=

(V1- V2)/2√3

r=

Vac/ Vdc

PRECAUTIONS:


1. The primary and secondary side of the transformer should be carefully identified

2. The polarities of all the diodes should be carefully identified.

RESULT:-

The ripple factor of the Full-wave rectifier (with filter and without filter) is calculated.

VIVA QUESTIONS:-

1. Define regulation of the full wave rectifier?

2. Define peak inverse voltage (PIV)? And write its value for Full-wave rectifier?

3. If one of the diode is changed in its polarities what wave form would you get?

4. Does the process of rectification alter the frequency of the waveform?

5. What is ripple factor of the Full-wave rectifier?

6. What is the necessity of the transformer in the rectifier circuit?

7. What are the applications of a rectifier?

8. What is meant by ripple and define Ripple factor?

9. Explain how capacitor helps to improve the ripple factor?

10. Can a rectifier made in INDIA (V=230v, f=50Hz) be used in USA (V=110v, f=60Hz)?


2. UJT CHARACTERISTICS

AIM: To observe the characteristics of UJT and to calculate the Intrinsic Stand-Off Ratio (η).

APPARATUS:

Regulated Power Supply (0-30V, 1A) - 2Nos

UJT 2N2646

Resistors 10kΩ, 47Ω, 330Ω

Multimeters - 2Nos

Breadboard

Connecting Wires

CIRCUIT DIAGRAM


THEORY:

A Unijunction Transistor (UJT) is an electronic semiconductor device that has only one

junction. The UJT Unijunction 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 interbase resistance.The original unijunction 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.

Circuit symbol

The UJT is biased with a positive voltage between the two bases. This causes a potential

drop along the length of the device. When the emitter voltage is driven approximately

one diode voltage above the voltage at the point where the P diffusion (emitter) is,

current will begin to flow from the emitter into the base region. Because the base region

is very lightly doped, the additional current (actually charges in the base region) causes

(conductivity modulation) which reduces the resistance of the portion of the base

between the emitter junction and the B2 terminal. This reduction in resistance means

that the emitter junction is more forward biased, and so even more current is injected.

Overall, the effect is a negative resistance at the emitter terminal. This is what makes the

UJT useful, especially in simple oscillator circuits. When the emitter voltage reaches V p,

the current starts to increase and the emitter voltage starts to decrease. This is

represented by negative slope of the characteristics which is referred to as the negative


http://en.wikipedia.org/wiki/Image:UJT_symbol.JPG

resistance region, beyond the valley point, RB1 reaches minimum value and this region,

VEB proportional to IE.

PROCEDURE:

1. Connection is made as per circuit diagram.

2. Output voltage is fixed at a constant level and by varying input voltage

corresponding emitter current values are noted down.

3. This procedure is repeated for different values of output voltages.

4. All the readings are tabulated and Intrinsic Stand-Off ratio is calculated using

η = (Vp-VD) / VBB

5. A graph is plotted between VEE and IE for different values of VBE.

MODEL GRAPH:


OBSEVATIONS:

VBB=1V VBB=2V VBB=3V

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

CALCULATIONS:

VP = ηVBB + VD

η = (VP-VD) / VBB

η = ( η1 + η2 + η3 ) / 3

RESULT: The characteristics of UJT are observed and the values of Intrinsic Stand-Off

Ratio are calculated.

VIVA QUESTIONS

1. What is the symbol of UJT?

2. Draw the equivalent circuit of UJT?

3. What are the applications of UJT?

4. Formula for the intrinsic stand off ratio?

5. What does it indicates the direction of arrow in the UJT?

6. What is the difference between FET and UJT?

7. Is UJT is used an oscillator? Why?

8. What is the Resistance between B1 and B2 is called as?

9. What is its value of resistance between B1 and B2?

10. Draw the characteristics of UJT?


19. SILICON-CONTROLLED RECTIFIER(SCR)

CHARACTERISTICS

AIM: To draw the V-I Characteristics of SCR

APPARATUS: SCR (TYN616) Regulated Power Supply (0-30V) Resistors 10kΩ, 1kΩ Ammeter (0-50) µA Voltmeter (0-10V) Breadboard Connecting Wires.

CIRCUIT DIAGRAM:

THEORY:


It is a four layer semiconductor device being alternate of P-type and N-type silicon. It consists

of 3 junctions J1, J2, J3 the J1 and J3 operate in forward direction and J2 operates in reverse

direction and three terminals called anode A, cathode K, and a gate G. The operation of SCR can

be studied when the gate is open and when the gate is positive with respect to cathode.

When gate is open, no voltage is applied at the gate due to reverse bias of the junction J2 no

current flows through R2 and hence SCR is at cut off. When anode voltage is increased J2 tends

to breakdown.

When the gate positive, with respect to cathode J3 junction is forward biased and J2 is reverse

biased .Electrons from N-type material move across junction J3 towards gate while holes from

P-type material moves across junction J3 towards cathode. So gate current starts flowing, anode

current increase is in extremely small current junction J2 break down and SCR conducts heavily.

When gate is open thee break over voltage is determined on the minimum forward voltage at

which SCR conducts heavily. Now most of the supply voltage appears across the load

resistance. The holding current is the maximum anode current gate being open , when break

over occurs.


PROCEDURE:

1. Connections are made as per circuit diagram.

2. Keep the gate supply voltage at some constant value

3. Vary the anode to cathode supply voltage and note down the readings of voltmeter and

ammeter. Keep the gate voltage at standard value.

4. A graph is drawn between VAK and IAK .

OBSERVATION

VAK(V) IAK ( µA)

MODEL WAVEFORM:


RESULT: SCR Characteristics are observed.

VIVA QUESTIONS

1. What the symbol of SCR?

2. IN which state SCR turns of conducting state to blocking state?

3. What are the applications of SCR?

4. What is holding current?

5. What are the important type’s thyristors?

6. How many numbers of junctions are involved in SCR?

7. What is the function of gate in SCR?

8. When gate is open, what happens when anode voltage is increased?

9. What is the value of forward resistance offered by SCR?

10. What is the condition for making from conducting state to non conducting state?


Edc 2

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