Bee Manual 2014

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SWARNADHRA COLLEGE OF ENGINEERING & TECHNOLOGY

SEETHARAMPURAM, NARASAPUR.

FOR

BASIC ELECTRICAL & ELECTRONICS ENGINEERING LAB OBSERVATION

(Section B: ELECTRONICS ENGINEERING)

Swarnandhra

Mr. V Satya Kishore

SWARNANDHRA COLLEGE OF ENGINEERING AND TECHNOLOGY

(Approved by AICTE, Accredited by NBA, Permanently affiliated to JNTU, KAKINADA)

SEETHARAMPURAM, NARSAPUR-534280. W.G.DT.,

DEPARTMENT OF ELECTRONICS & COMMUNICATION engineering

II YEAR B.Tech MECHANICAL ENGINEERING

Prepared by:

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S.NO NAME OF THE EXPERIMENTDATE OF FACULTY

COMPLETION SIGNATURE

Study and operations of

Multimeters

Function Generator

Regulated Power Supplies

Study and Operation of CRO

SWARNADHRA COLLEGE OF ENGINEERING & TECHNOLOGY

SEETHARAMPURAM, NARASAPUR - 534 280

LIST OF EXPERIMENTS (Part -B)

Bread Boards

1. PN Junction Diode Characteristics

3. Full Wave Rectifier

4.

5. RC Phase Shift Oscillator.

6 Class ‘A’ Power Amplifier..

with and without filter. CE Transistor Amplifier.

2. Transistor CE Characteristics

(input and output).

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BREAD BOARD

Basically breadboards are modules having numerous discrete tiny spring-loaded sockets arranged in definite

rows and columns. These rows and columns are linked group wise internally through copper tracks in smart

patterns which may be diversely suited to vastly different circuit design applications. By just following these

built-in connections carefully, many circuit integrations and combinations may be created by simply inserting

the component leads and jumper wires into the relevant randomly selected sockets.

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STUDY AND OPERATION OF

1. MULTIMETER

2.FUNCTION GENERATOR

3.REGULATED POWER SUPPLY.

4.CRO

1(A).STUDY OF MULTIMETER:

Sepcifications:

Display: 3 ½ digit liquid crystal display (LCD)with a maaximum reading of 1999.Polarity:Automatic,Positive implied,negative Polarity indication.

Overrange: (1) or (-1) is displayed.

Zero:Automatic.

Battery life: 200 Hours typical with carbon-zinc.

DC Volts:

Ranges: 200mv,2v,20v,200v,600v.

Resolution: 100µv.

Accuracy: ±(0.8% rdg + 1 dgt).

Input Impedance: 10 M Ω

Over Load Protection: 600v DC or AC rms.

DC Currents:

Ranges: 200µA,2mA,20mA,200mA,10A.

Accuracy: ±(1.0% rdg + 1 dgts) on 200µA to 200mA ranges

±(3.0% rdg +3 dgts) on 10A range.

Input Protection: 0.5A/ 250V Fast blow fuse

10A/600V fast blow ceramic fuse.

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AC Current:

Ranges : :(50Hz-500Hz)

Ranges: 200µA,2mA,20mA,200mA,10A.

Accuracy: ±(2.0% rdg + 4dgts) on 200µA to 200mA ranges

±(3.5% rdg +4dgts) on 10A range.

Input Protection: 0.5A/ 250V Fast blow fuse 10A/600V fast blow ceramic fuse.

Resistance:

Ranges:200Ω, 2KΩ, 20KΩ, 200KΩ,2000KΩ, 20MΩ, 2000MΩ

Accuracy: ±(1.0% rdg + 4dgts) on 200Ω to 2000KΩ ranges

±(2.0% rdg + 4dgts) on 20MΩ range

±[(5.0% rdg - 10dgts)+ 10dgts] on 2000MΩ range

Open circuit volts: 0.3VDC

(3.0VDC on 200Ω,2000MΩ ranges)

Overload protection:

500VDC or AC rms

Continuity:

Audible indication: less than 100Ω

Overload protection: 500VDC or AC rms

Diode test:

Test current: 0.8mA ±0.3mA

Accuracy:(3.0% rdg +1dgt)

Open circuit volts: 3.0V DC typical

Overload protection: 500V DC or AC rms

Capacitance:

Ranges: 2nF,20nF,200nF,2µF,20µF

Accuracy:±(4.0%rdg+10dgts) on all ranges

Test frequency:400Hz

Transistor hFE:

Ranges:0-1000

Base current: 10µAdc approx. (Vce=3.0V DC)

Fornt Panel Controls:

Power switch: switch on power supply for bringing into the operating mode

Rotary switch: It is used to select desire measurement in desired range

AC/DC switch:put the switch in AC mode to measure AC current as well as AC voltage.

Put the switch in DC mode to measure DC current as well as DC voltage

ebce: This is used to put transistor in this holes for measure hfe value

CX : It is used to place the capacitor terminals in this holes for measure capacitance value

V,COM,10A: Jacks for connecting multi meter probes

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1(B).OPERATION:

Voltage measurements:

1. Connect the red test lead to the "VΩ" jack and the black test led to the "COM" jack.

2. Set the Function/Range switch to the desired voltage range and slide the "AC/DC" selector switch to

the desired voltage type. If magnitude of voltage is not known, set switch to the highest range andreduce until a satisfactory reading is obtained.

3. Connect the test leads to the device or circuit being measured.

Current measurements:

1. Set the Function/Range switch to the desired current range and slide the "AC/DC" selector switch to

the desired current type.

2. For current measurements less than 200mA,connect the red test lead to the µA/mA jack and the black

test lead to the COM jack.

3. For current measurements of 200mA or greater, connect the red test lead to the 10mA jack and theblack test lead to the COM jack.

4. Remove power from the circuit under test and open the normal circuit path where the measurement is

to be taken. Connect the meter in series with the circuit.

Resistance and continuity measurements:

1. Set the Function/Range switch to the desired resistance range or continuity position.

2. Remove power from the equipment under test.


4. Touch the probes to the test points. In ohms,the value indicated in the display is the measured value of resistance. In continuity test, the beeper sounds continuously, if the resistance is less than 100Ω.

Diode tests:


2. Set the Function/Range switch to the "diode" position.

3. Turn off power to the circuit under test.

4. Touch probes to the diode. A forward-voltage drop is about 0.6V(typical for a silicon diode).

5. Reverse probes. If the diode is good, "1" is displayed. If the diode is shorted. ".000" or another number

is displayed. If the diode is open. "1" is displayed in both directions.

Transistor gain measurements:

1. Set the Function/Range switch to the desired hfe range (PNP or NPN type transistor).

2. Never apply an external voltage to the hfe sockets. Damage to the meter may result.

3. Plug the transistor directly into the hfe sockets. h

fe sockets are labeled E,B, and C for emitter, base,

and collector.

4. Read the transistor hfe directly from the display.

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Capacitance measurements:

1. Set the Function/Range switch to the desired Cx(capacitance) range.

2. Never apply an external voltage to the Cx sockets. Damage to the meter may result.

3. Insert the capacitor leads directly into the Cx sockets.

4. Read the capacitance directly from the display

Precautions:

1. Use caution when working above 60V DC or 150V AC rms. Such voltages Cause a shock hazard.

2. When using the probes, keep your fingers behind the finger guards on the probes.

3. Measuring voltage which exceeds the limits of the multi meter may damage the meter and

expose the operator to a shock hazard. Always recognise the meter voltage limits as stated on the front

of the meter

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2(A).STUDY OF FUNCTION GENERATOR:

Specifications:

Operating modes : Sine,square,triangle,pulse

Frequency range : 2Hz to 2MHz in six decade steps, variable control between steps

Accuracy : 1% of the selected range ± counts

Sine wave distortion : 1% typical

Square/pulse rise and fall time : less than 100ns at full rated output

Pulse duty cycle variation : 15% to 85%Triangle linearity error : 0.5%

Display : 5 digits

Frequency range : 2Hz to 2 M Hz

Input impedance : 500kohms/22pf

Accuracy : count ±0.1Hz

Outputs:

Signal output : (SHORT CIRCUIT PROOF)

Impedance : 500 ohms/600 ohms switchable

Output : Max 25v p-p into 50ohms

Attenuation : 4 steps :20db,40db,60db

Level flatness : +-2% from 1Hz to 100k Hz

DC offset : Continuously variable

Offset range : ±Continuously adjustable attenuated by step attenuator

Front Panel Controls

Frequency counter jack: Frequency counter for the external signal. there is a switch side by this connector

enabling user to select the external signal.

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F.var(adjusting knob) : Continuous and linear frequency adjustment from 2Hz to 2 M Hz in steps selected with

frequency range

Offset (on/off): Adjusting of the positive/negative offset voltage. controls the output ±15 signal dc level with

respect to ground.

Amplitude control: It adjust the amplitude of the output signal from less than 10% to 100%(20Hz to 20MHz)

Range selector: (6 positions push button switches) used in conjunction with F VAR to select the desired output

frequency . the switch has six distinct positions starting at 20Hz to 2MHz. this corresponds to upper frequency

limit in any range shows below.

Duty cycle: this controls varies the duty cycle of the selected pulse from 15% to 85%(20Hz to 2MHz)

Function selector: (4 positions push button switch) selects either sine ,square, triangle or pulse as the output waveforms

Attenuator: (-20 db to -40db push button). The switch adjusts the amplitude of output signal in precise steps

of 20db .maximum attenuation obtained is 60 db.

2(B).OPERATION:

1.Release the all push buttons before using the instrument

2.Switch on the instrument

3.Keep the offset switch in off position

4.Select the frequency ranges as you required

20HZ : 2 to 20HZ

200HZ :20hz to 200HZ

2KHZ: 200hz to 2KHZ

20KHZ: 2KHZ to 20KHZ

200KHZ : 20KHZ to 200KHZ2MHZ: 200KHZ to 2MHZ

5.Select the waveform

6.Connect the BNC to crocodile connector as the function o/p terminal

7.Observe the different waveforms at different frequency

8.Release the all push buttons before switch off the instrument

9.Do not apply any dc voltage to the o/p terminal of the instrument.

Precautions:

1. When the instrument is used to make measurements of high voltage there is always

certain amount of danger from electrical shock

2. Do not operate the instrument with the covered removed unless you are a qualified service technician.

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3(A).STUDY OF TRANSISTORISED POWER SUPPLY:

Specifications:

Input Voltage: 230V +\-10% 50HZ, Single Phase AC.

Output Voltage:

(1) Volts (Settable by the FINE & COARSE Controls on the front panel)

(2) Output through Terminals.

3. Load Current: 0-1 Amp, Maximum (Continuously Variable by front panel current control).

4. Regulations :- (LINE) CV Mode: 0.01% (for +\-10% change in mains supply) Better than +\- 0.05 %

of the highest specified output voltage from no load to full load.

5. Ripple & Noise: ImV

r.m.s

6. Protections: Constant Current limiting type of output characteristics protects the unit from over load,short circuit conditions.

7. Metering: Digital Voltmeter and Ammeter provide, to read output Voltage and Current.

Operating temparature: 0-55 °C Ambient

Front Pannal Controls:

Volt Switch: Display Channal 1, or Channal 2 Output voltge on DVM.

Current Switch : Display Channal 1, or Channal 2 Current on DAM

Core: Produces wide variations of output voltge in steeps of .5 Volts.

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Fine: Produces light variation of output voltage in steeps of .1 Volts.

Current limite:Adjust maximum current rating of source

3.(B) OPERATION:

Before switching the unit “ON” first observe the following :

1. The input ON/OFF switch “OFF” position.

2. Plug the input mains cord in an appropriate socket and switch “ON” the ON/OFF” switch. The Neon/

LED will glow indicating the availability of the input supply.

3. Power Supply output settings

a) Voltage Setting: The Power Supply Unit has automatic cross over type of output characteristics The

cross over point is decided by the set output voltage level and set current limit. The output voltage can be

set to the desired level by adjusting control on the front panel without connecting load.

b) Current Setting : The Output current can be set by decreasing the current potentiometer to minimum

position (anti clock wise); short the + VE & -VE terminals and adjust required current. Remove the short

circuit and load the unit. The power supply will work within the set current limit and output voltage.

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4(A) STUDY OF CRO:

Specifications:

Max AC frequency : 5 MHz.

Max AC Voltage : 50V.

Max DC Voltage : 50V

Min AC, DC Voltage : 1 uV

X-Y mode of operation

Dual Trace.

Front Pannal Controls:

Power : Pushbutton switch to turn scope ON and OFF. LED indicates

(PB Switch + LED) : 'POWER ON' condition.

Intensity : Intensity control to adjust Brightness of CRT display.

(Knob)

Focus : Focus control to adjust Sharpness of CRT display.

(Knob)

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X-Y : Switch when pressed, cuts off Internal Time base and selects X-Y

(PB Switch) : operation. (X signal via CH.II)

X-Pos : Controls Horizontal Positioning of trace.

(Knob)

Hold Off : Controls Hold Off time between Sweeps in the ratio 1: 1 0approx. (Knob) : (Normal (Cal) position = full counterclockwise.)

Trig : LED glows, if Sweep is triggered.

(Led)

TV Sep : TV sync separator.

(Lever switch) OFF = Normal operation.

TV: H = Line or Horizontal Frequency.

TV: V = Frame or Vertical Frequency.

+/- : Selects the Slope of Trigger Signal.(PB Switch) + = rising edge.

- = falling edge.

Time/Div : Selects Time base speeds from O.5~S/div. to O.2mS/div.

(Rotary)' switch)

Variable : Timebase variable control.

(Center knob) Increases Timebase speed in the ratio 1: 2.5 approx.

(Led) Cal. Position = full counterclockwise, LED OFF.

Uncal Position = LED ON,

Ext : Switch when pressed selects External Triggering.

(PB Switch) (Trigger signal via TRIG.INP. 15)

Switch when in out position, selects Internal' Triggering.

Trig. Inp : Input for External Trigger Signal.

(BNC connector)

Level : Adjusts trigger point of the Signal from +ve peak to -ve peak,

(Knob) if AT/NORM PB switch (16) is pressed.

X-Mag x10 : Switch when pressed, magnifies Trace or Signal 10 times in

(PB Switch) X-direction. On 0.5J1S/div. range, this improves timebase speed

to 50nS/div.

Cal 0.2V I2V : Calibrator output sockets provided for probes compensation.

(2mm socket) Signal available at the sockets is flat top square wave,

of amplitude 0.2Vpp and 2Vpp, frequency = 1kHz approx.

0.2Vpp used for 10: 1 probes compensation.

2Vpp used for 100: 1 probes compensation.

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CT : Switch when pressed converts the instrument from oscilloscope

(PB Switch & to Component Tester Mode

4mm socket).

One test lead is connected to CT socket and the second test lead is

connected to ground (24. or 36.) socket.

Y-Pos : Controls Vertical positioning of CH.I trace.(Knob)

Invert (Ch 1)' : Switch when pressed, inverts the polarity of CH.I signal.

(PB Switch) In combination with ADD switch, used for algebraic addition or

difference of two channels,

Ch.I : Signal input for CH.I, Input Impedance IM? ? 25pF.

(BNC connector)

Ground : Separate Ground socket.

(4mm socket)

AC/DC/GD : Input coupling switches for CH.I

(PB Switches) AC: Both switches in out position.

Signal is capacitively coupled, DC is blocked.

DC: AC/DC switch pressed, GD switch in out position.

All components (AC & DC) of the signal are passed.

GD: GD switch pressed. AC/DC switch may be at any position.

Signal is disconnected, UP of vertical amplifier is

grounded.

Volts/Div : CH.I Input Attenuator. Selects input sensitivity in mV/div.

(Rotary switch) or V/div. in 1-2-5 sequence

Var-Gain : Continuously variable gain between the calibrated positions of

(Center knob) the VOLTSIDIV. switch for CH.I.

(LED) Increases sensitivity by a ratio 1: 2.5

Cal. Position = fully counterclockwise, LED OFF.

Uncal. Position = LED ON.

On Smv range, when knob turned fully clockwise, sensitivity

becomes 2m V. .

Dual : Switch in out position = Single Channel separately.

(PB Switch) Only DUAL Switch pressed = CH.I & CH.n in alternate mode.

DUAL+ADD switches pressed = CH.I & CH.n in CHOP mode.

Add : Only ADD switch pressed = Algebraic addition or difference of

(PB Switch) CH.I & CH.n, in combination with INVERT switches.

Volts/Div : CH.n Input Attenuator. Selects input sensitivity in mV/div. or

(Rotary switch) V/div. in 1-2-5 sequence

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1. AMPLITUDE MEASUREMENT :

VOLTAGE VALUES OF A SINE CURVE

PRODEDURE:

1. Take the signal generator and switch on the power supply

2. Push the sine function switch and observe whether the dc off-set switch is in ON position. If it is

in ON position, move it to OFF position.

3. Push any one of the maximum range switch

4. Set the frequency range potentiometer at middle position (Now the signal generator generates a

sine signal of approximately 500Hz).

5. Set the amplitude control at middle position.

6. Observe whether any attenuation button (dB buttons) is pressed or not. If these buttons are

pressed, release them.

7. Take the C.R.O and switch on the power supply.

8. Press channel 1 (CH-I) buttton. Check for the appearance of any horizontal line.

9. If the line doesn't appear, slightly vary the vertical and horizontal position controls of CH-I, until

the line appears focused at the centre of the screen.

10. If horizontal line appears in a thick or thin fashion, vary the focus control until the generated line

appears clearly.

11. Push the C.R.O. ac/dc button in a.c position. Observe whether the ground button is pushed or

not.If it is pushed then release it.(If the ground button is pushed, the C.R.O. does not take any

input signal)

12. Take the C.R.O. probe, connect output of the signal generator to the input to CH-1 of the C.R.O

13. Observe the waveform on the screen of the C.R.O. If the signal appears with less amplitude

decrease the amp/div rotary switch until the waveform amplitude increases on the screen. If the

signal that appears on the screen is out of range of the screen, increase the amp/div rotary switch

until the wave form appears on the screen inbetween the graticules.

14. Observe the waveform on the C.R.O. screen. If the waveform appears compressed, decrease time

/div and if it appears expanded increase time/div rotary switch, until a perfect waveform appears

on the screen.

15. After getting clear waveform on the screen, note the number of divisions between the peak to

peak amplitude of the signal in “Y” axis.

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16. Note the values in tabular form and calculate the peak amplitude and r.m.s voltage of the input

signal using the formula.

17. Change the amplitude of signal generator and repeat steps 15 and 16.

S.NO: No.of div between VP-P

= N x V VP=V

P-P /2 Vrms=V

P / √2

Peak to Peak in‘y’ axis (N)

1

2

3

4

2. FREQUENCY MEASUREMENT

Using CRO we cannot directly measur Frequency. We calcute the Frequency by measuring Time Period of

signal.

PRODEDURE:

1. Take the signal generator and switch on the power supply

2. Push the sine function switch and observe whether the dc off-set switch is in ON position. If it is

in ON position, move it to OFF position.

3. Push any one of the maximum range switch4. Set the frequency range potentiometer at middle position (Now the signal generator generates a

sine signal of approximately 500Hz).

5. Set the amplitude control at middle position.

6. Observe whether any attenuation button (dB buttons) is pressed or not. If these buttons are

pressed, release them.

7. Take the C.R.O and switch on the power supply.

8. Press channel 1 (CH-I) buttton. Check for the appearance of any horizontal line.

9. If the line doesn't appear, slightly vary the vertical and horizontal position controls of CH-I, untilthe line appears focused at the centre of the screen.

10. If horizontal line appears in a thick or thin fashion, vary the focus control until the generated line

appears clearly.

11. Push the C.R.O. ac/dc button in a.c position. Observe whether the ground button is pushed or

not.If it is pushed then release it.(If the ground button is pushed, the C.R.O. does not take any

input signal)

12. Take the C.R.O. probe, connect output of the signal generator to the input to CH-1 of the C.R.O

Amp/

Div(V)

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13. Observe the waveform on the screen of the C.R.O. If the signal appears with less amplitude

decrease the amp/div rotary switch until the waveform amplitude increases on the screen. If the

signal that appears on the screen is out of range of the screen, increase the amp/div rotary switch

until the wave form appears on the screen inbetween the graticules.

14. Observe the waveform on the C.R.O. screen. If the waveform appears compressed, decrease time

/div and if it appears expanded increase time/div rotary switch, until a perfect waveform appears

on the screen.

15. After getting clear waveform on the screen, note the number of divisions between the peak to

peak amplitude of the signal in “X” axis.

16. Note the values in tabular form and calculate the peak amplitude and r.m.s voltage of the input

signal using the formula.

17. Change the Frequency of signal generator and repeat steps 15 and 16.

S.NO: No.of div between Time/Div (t) Signal Time Period Frequency

Peak to Peak in T = N X

t F=1/ T (Hz)‘X’ axis (N)

1

2

3

4

5

3. PHASE DIFFERENCE MEASUREMENT

PROCEDURE:

1. Apply 2KHz sine signal from the signal generator with an amplitude of approximately 5V.

2. Set the C.R.O in dual mode by pressing the dual button on the front panel of the C.R.O

3. Connect input signal of the circuit to CH-I input and output of the circuit to CH-II input of

C.R.O.

4. Vary amp/div control, time/div control until two perfect waveforms on the C.R.O screen

appear.

1k Ω

1µFsignal generator i/p out put

Circuit Diagram

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1. P-N JUNCTION DIODE

AIM: 1) To plot the V-I characteristics of a diode under forward and reverse bias conditions.

2) To find the Static (dc) resistance (rd) and Dynamic (ac) resistance (r

ac).

EQUIPMENT &COMPONENTS REQUIRED:

S.NO. EQUIPMENT/COMPONENTS SPECIFICATION QUANTITY

REQUIRED

1 (TPS) TRANSISTORISED 0-30V 1

POWER SUPPLY

2 DIODE 1N4007 1

3 RESISTOR 470Ω 1

4 DIGITAL AMMETERS (DC) 0-100 mA, 1

0-500 µA 1

5 BREAD BOARD WB-102 1

6 DIGITALVOLT METERS (DC) 0-1V, 1

0-30V 1

THEORY:

The basic property of the diode is its unidirectional current flow. The diode has two terminals called the

anode and cathode. If the positive terminal of the power supply is connected to the anode and negative terminal

of the supply is connected to the cathode, then the diode is said to be forward biased. When Forward Voltage >

internal barrier Voltage the potential barrier at the junction completely disappears, resulting in relatively large

current flows in the external circuit. There must be at least 0.7V forward bias voltage for silicon diodes before

it can conduct appreciably. This voltage is known as cut-in voltage or threshold voltage (Vth).

If the positive terminal of the power supply is connected to the cathode and negative terminal of the

supply is connected to the anode, the diode is said to be reverse biased. Due to the minority carriers, there is a

small current flow. It will usually be a few microamperes. The reverse biased current of a diode is very small

compared to the forward biased current. The reverse biased current is also known as leakage bias current. The

reverse voltage at which the junction breakdown occurs is known as breakdown voltage, VBD

. The reverse

biased current is a function of temperature.The volt -ampere characteristics is shown in the figure1.3. An Ideal diode acts like a switch, either open

or closed, depending upon the polarity of the voltage placed across it. The ideal diode has zero resistance under

forward bias and infinite resistance under reverse bias.

CUT-IN VOLTAGE:

The term cut-in voltage, indicated by Vth

, is the voltage below which the current is very small. As the

voltage exceeds cut-in voltage, the current increases very rapidly. The cut-in voltage is some times called offset

voltage, break point voltage or threshold voltage.

18

Exp. No.

Date:

3) To find Cut in voltage (Threshold voltage (Vth))

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Cut-in voltage for Germanium diode is 0.2 V and about 0.6V for Silicon diode.

DYNAMIC (ac) RESISTANCE:

The a.c. resistance of a diode, at a particular D.C. voltage, is equal to the reciprocal of the slope of the

characteristic at that point, i.e. the a.c. resistance, rac

= ∆V/ ∆I. The resistance offered by the diode to an a.c.

signal is called its dynamic or a.c. resistance. The resistance calculated using the relation ∆V/ ∆I is called the acor dynamic resistance(r

dc).

Hence we will refer to the ac resistance of the diode as rD where the lower case letter r is in keeping with

the convention of using lower case letters for ac quantities. Thus rac

= ∆V/ ∆I Ω. The value of a.c. resistance of

a diode is in range of 1 to 25Ω usually it is smaller than the D.C. resistance of a diode.

STATIC (dc) RESISTANCE:

When dc voltage is applied across the diode certain dc current will flow through it. The dc resistance of

a diode is found by dividing the dc voltage across it by the dc current through it. Thus the dc resistance also

called the static resistance is found by direct application of Ohms law. This is denoted by rdc

. rdc

= V/I Ω. The

static resistance of diode is quite low (in ohms)

CIRCUIT DIAGRAMS:

a) FORWARD BIAS (FB) :

470Ω (0-100) mA

+

+ A +

T.P.S (0-30) V 1N4007 (0-1) V

K

b) REVERSE BIAS (RB) :

470Ω (0-500)µA

+ -

+ K

T.P.S (0-30) V 1N4007 (0-30)v

19

V

fig.1.1

A

V

+

A

fig.1.2

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PROCEDURE:

1.Connect the circuit as per the diagram (Forward bias).fig.1.1

2. Vary the T.P.S in sequence of steps and take the corresponding voltmeter and ammeter readings. and

Note in Table 1.1

3.Similarly connect the circuit as per the diagram (Reverse bias).fig.1.2

4. Vary the T.P.S.in sequence of steps and take the corresponding voltmeter and ammeter readingsand

Note in Table .1.2

5. Plot the graph between V-I characteristics in Forward bias and Reverse bias for different values. Take

V (Voltage) on X Axis and I (Current) on Y-axis.

6. Calculate (a) static resistance (rdc

) = V/I Ω.

(b) Dynamic resistance (rac

)= ∆V/ ∆I Ω.

(c) Cut in voltage (Threshold voltage (Vth))

OBESERVATION TABLE:

FORWARD BIAS:

S.No Forward voltage Forward current

(VF) volts (I

F) mA

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Table1.1

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REVERSE BIAS:

S.No Reverse voltage Reverse current

(VR) volts (I

R) µA

MODEL GRAPH:

∆V =(V2-V1) Small Change in forward voltage.

∆I = (I2-I1) Small Change in reverse current.

21

Table1.2

I2

I

IF mA

- I mA

VB -VR(volts)

? I

? V

V1 V2

VF(volts)

∆

∆

(IR) µA

Fig 1.3

D

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RESULT:

VIVA - QUESTIONS:

1. How do you define barrier potential?

2. What is the difference between static and dynamic resistance in case of diode?

3. How capacitance is formed in a diode?

4. Explain why the PIV of semiconductor diode is an important parameter?

5. Write the diode current equation. 6. Is reverse saturation current independent of forward and reverse bias?

7. What are the applications of a diode?

8. What are the specifications of a diode?

9. What is the cut in voltage?

REMARKS:

Signature of Faculty

Y

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2. COMMON-EMITTER CONFIGURATION

AIM: To draw the input and output characteristics of a transistor in Common - Emitter configuration.

EQUIPMENT & COMPONENTS REQUIRED:


REQUIRED

1 TRANSISTOR BC 107 1

2 AMMETER (0-100m A) 2

3 VOLTMETER (0-1V) 1

(0-30V) 1


5 T.P.S (0-30V)/1A 1

6 CONNECTING WIRES 10

7 AMMETER (0-500µA) 1

8 RESISTORS 10 KΩ 1

100Ω 1

THEORY:

The common emitter configuration is derived from the fact that the emitter is common to both the

input and output side of the configuration. The input is applied between base and emitter and output is taken

from collector and emitter. Here emitter is common to both the input and output terminals. Two sets of

characteristics are necessary to describe the behavior of the CE configuration. One for the input or base-

emitter circuit and the other for the output or collector -emitter circuit.

INPUT CHARACTERISTICS:

The input characteristics are plotted between the input current IB and the input voltage V

BE for different

values of output voltage VCE

.

1. The base current( IB) (µA) increases with the increase in base to emitter voltage (V

BE ) for

constant VCE

. This implies that input resistance (ri) of common emitter configuration is very

high as compared to CB configuration.

2 As the collector - emitter voltage (VCE ) is increased above 1v, the curves shift downward. Thisoccurs because of the fact that as V

CE is increased, the depletion width in the base- region

increases. This reduces the effective base width, which in turn reduces the base current.

3 Input resistance or dynamic (ac) input resistance of the transistor is the ratio of change in Base-

Emitter voltage (VBE

) to change in base current (IB) at constant Collector-Emitter Voltage (V

CE).

i.e; ri =∆ V

BE / ∆ I

B at constant V

CE.

Typical value of ri is few Hundred Ohms to 4K ohms.

Exp. No.

Date:

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OUTPUT CHARACTERISTICS:

These characteristics may be obtained by using the circuit shown in fig.no 2.1.

1. The output characteristics may be divided into three important regions namely saturation region,

active region and cut-off region.

2. As the collector - emitter voltage (VCE

) increases above zero, the collector current (IC) increases

rapidly to a saturation value, depending upon the value of base current (IB). It may be noted that

collector current (IC) reaches to a saturation value when V

CE is about 1V.

3. When VCE

is increased further, IC slightly increases. This increase in I

c is due to the fact that the

increased value of collector - emitter voltage (VCE

) reduces the base current and hence the

collector current increases. This phenomenon is called as an early effect.

4. When IB is zero, a small I

C current exists. This is called leakage current. However for all practical

purposes, the collector current (Ic) is zero, when IB is zero. Under this condition the transistor issaid to be cut-off.

5 Output resistance (or) dynamic (ac) output resistance is the ratio of change in collector voltage

(∆VCE

) to the change in collector current (∆Ic) at constant I

B i.e; R

o = ∆V

CE / ∆ I

c at constant I

B.

The common - emitter output resistance of a transistor ranges from 10KΩ to50KΩ

CIRCUIT DIAGRAM:

PROCEDURE (INPUT CHARACTERISTICS) :

1. Connect the circuit as per the circuit diagram.

2. Keep the VCE

voltage constant at 2v by changing TPS-2.

3. Now vary TPS-1 voltage from to 0 – 2V in steps of 0.1V and note down the VBE

voltage and IB base

current .

24

fig 2.1

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4. Repeat the steps 2 and 3 for VCE

= 4V and VCE

= 6V. and note the observation in table 2.1

5. Draw the graph between VBE

and IB and for different V

CE voltages.

OBSERVATION TABLE (INPUT CHARACTERISTICS):

VCE1

(V) VCE2

(V)

VBE(V)

IB(µA) V

BE(V)I

B(µA)

MODEL GRAPH:(INPUT CHARACTERISTICS):

PROCEDURE (OUTPUT CHARACTERISTICS) :

1. Connect the circuit as per the circuit diagram.fig 2.1

2. Keep the base current IB

constant at 400µA by changing TPS-1.

3. Now vary TPS –2 voltage from 0 – 12V in steps of 1V and note down the voltage across

collector and emitter VCE

and collector current IC.

4. Repeat steps 2 and 3 at IB = 450µA and I

B = 500µA.and note the observation in table 2.2

5. Draw the graph between VCE

and IC for different base currents I

B.

S.No

25

Table 2.1

fig 2.2

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OBSERVATION TABLE (OUTPUT CHARACTERISTICS):

IB1

(µA) IB2

(µA)

VCE

(V) IC(mA) V

CE(V) I

C(mA))

MODEL GRAPH:

S.No

Cutt- off

Region

Active

region

Saturation

Region

C o l l e c t o r c u r r

e n t I C ( m A )

Collector – emitter voltage (VCE)

IB = 0

IB = 3 (µA)

IB = 1(µA)

IB = 4 (µA)

IB = 2 (µA)

26

Table 2.2

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RESULT: -

VIVA - QUESTIONS :

1) What is meant by transistor? (BJT)

2) What are the terminals in a transistor?

3) What is current amplification factor?

4) What is ment by gain factor (or) transport factor means?

5) What are the applications of transistor?

6) What is the relation between amplification factor and gain factor?

7) What is early effect?

8) Define drift current?

9) Write down the current equation for transistor.

10) Mention CE applications.

REMARKS:


Y

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3. FULL WAVE RECTIFIER

AIM: a) To observe the function of full wave rectifier with and without filter.

b) To calculate the Ripple factor, % of regulation and efficiency (η).

EQUIPMENT AND COMPONENTS REQUIRED:

S.No. EQUIPMENT/COMPONENTS REQUIRED SPECIFICATION QUANTITY

1 TRANSFORMER (9-0-9) V 1

2 DIODE 1N4007 2

3 DECADE RESISTANCE BOX (DRB) (0-1) MΩ 1

4 DIGITAL MULTIMETERS (0-20V) 2


6 CAPACITOR 1000µF / 25V 1


THEORY:

A full-wave rectifier is a circuit. which allows a unidirectional current to flow through the load

during the entire input cycle.

The result of full wave rectification is a d.c output voltage that pulsates for every half-cycle of

the input. There are two types of full-wave rectifiers namely center-tapped and bridge rectifier.

Exp. No.

Date:

28

fig 3.1

D2

V

VS

VS

+

++

+_

_

_

_

D1

V0

+ i +

V

VS

VS

+

++

+_

_

_

_

D1

V0

+

i +

D2

_+

Fig (3)

Fig (2)

i

+

_

+

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WORKING:

The center-tapped full wave rectifier circuit uses two diodes, which are connected to the center-tapped

secondary winding of the transformer. The input is applied to the primary winding of the transformer. The

center-tap on the secondary winding of a transformer is usually taken as the ground or zero voltage reference

point. It may be noted that the voltage between the center-tap and either end of the secondary winding is half of

the secondary voltage,i.e.,VS=V

2 /2

The operation of a center-tapped full-wave rectifier:

During the positive half-cycle of the input the polarities of the secondary voltage are as shown in

figure this forward biases diode D1 and reverse-biases diode D2. As a result of this, diode D1 conducts some

current where as diode D2 is off. The current through load RL is as indicated in the above figure. It may be noted

that current through the load flows in the same direction, during both the positive and negative portions of the

input cycle. Therefore the output voltage is the voltage developed across the load RL.

Average values of output voltage and load current in a full-wave rectifier:

Consider a center-tapped full-wave rectifier with a sinusoidal a.c. input voltage.

Let Vm= Maximum value of the voltage across each half of the secondary winding.

We know that r.m.s value of secondary voltage is Vrms

=Vm / √2.

Vs = the r.m.s.value of the voltage across each half of the secondary winding.

Im = Maximum value of the load current.

Vdc

=Average or dc value of the output voltage across the load resistor.

Idc

= Average or dc value of the current through the load resistor.

Vs = Vm Sin ω tWhere V

s= instantaneous value of the voltage across each half of the secondary winding

Vdc

=2 Vm / π =0.636 V

m

The average (or) dc value of the load current is given by the relation:

Idc

=Vdc /R

L =2V

m /(πxR

L)=2I

m / π = 0.636 I

m (since I

m= V

m /R

L)

=2Im / π = 0.636I

m

Peak inverse voltage:

We know that each diode in a full wave rectifier is alternately forward biased and reverse biased. The

maximum value of reverse voltage which the diode must withstand is twice the maximum secondary voltage

(i.e; 2Vm) Consider the circuit of a center tapped full wave rectifier. Peak inverse voltage is the maximum

possible voltage across a diode when it is reverse biased. Consider that D1is in forward biased i.e, it is conducting

and diode D2 is reverse biased i e; non conducting. In this case a voltage V

mis developed across the load

resistor RL.

Now the voltage across diode D2is the sum of the voltage across load resistor R

L and voltage across

the lower half of transformer secondary Vm. Hence PIV of diode D

2= V

m+V

m= 2V

m. Similarly PIV of diode D

1

is 2Vm . PIV of each diode in a center tapped full wave rectifier is PIV=2V

m

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CIRCUIT DIAGRAMS: (Without Filter)

PROCEDURE:(Without Filter)

1) Connect the circuit as per the circuit diagram.fig 3.2

2) First take the no load voltage without connecting the DRB

3) Connect the multimeter across the output terminals

4) Now connect the DRB, set the DRB at 500Ω and take the readings of Vac

and Vdc

by using

the multimeter.

5) Repeat the above step by decreasing DRB in the order of 500Ω to 100Ω and note the read-

ings of Vac

and Vdc

with the multimeter.

6) Calculate the Vac and V

dcripple factor (γ ) = V

ac / V

dc.

7) Calculate the % regulation (η) =[ (Vnoload

– Vfull load

) / Vfull load

]x 100

TABLE: (Without Filter)

Vno load

(v)=

RL (Ω) V

dc(V) V

ac(V) Ripple Factor (η) %Regulation (η)

A D1 K

Ph

N

VS = V2 /2

V2 V1

A D2 K

RL

VS = V2 /2

AC

230V/50Hz

CRO(Vo)

1N4007

1N4007

9V

9V VO or

Vac or

Vdc

fig.3.2

30

Table 3.2

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I n p u t v o l t a g e ( v i n )

0

V m

T i m eπ 2π

Vm

O u t p u t v o l t a g e ( v o u t )

Time2π π 0

+

-

A D1 K

2

9V

9V

O

1N4007

1N4007

VO or

Vac or

Vdc

Ω

fig.3.3

WAVEFORMS:(Without Filter)

PROCEDURE: (With Filter)

1) Connect the circuit as per the circuit diagram.3.3

2) First take the no load voltages (Vac

and Vdc

) without connecting the DRB.

3) Now connect the DRB, set the DRB at 500 Ω and take the readings of Vac

and Vdc

by using

the multimeter.

4) Repeat the above step by decreasing DRB in the order of 500Ω to 100Ω note the readings of

Vac

and Vdc

with the multimeter.

5) Calculate the Vac

and Vdc

ripple factor (γ ) = Vac

/ Vdc.

6) Calculate the % regulation (η) =[ (Vnoload

– Vfull load

) / Vfull load

]x 100

CIRCUIT DIAGRAMS: (With Filter)

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TABLE:(With Filter)

Vno load

(v)=

RL (Ω) V

dc(V) V

ac(V) Ripple Factor (γ ) %Regulation (η)

WAVEFORMS:(With Filter)

RESULT:

I n p u t v o l t a g e ( v i n )

0

V m

T i m eπ 2π

32

Table 3.3

Vm

O u t p u t v o l t a g e ( v o u t )

Time2π π 0

fig 3.4

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VIVA - QUESTIONS :

1) What is a full wave rectifier?

2) What are the types of full wave rectifiers?

3) What is the theoretical efficiency for full wave rectifier?4) What is meant by ripple and ripple factor of full wave rectifier?

5) Explain the operation of full wave rectifier.

6) What are the applications of full wave rectifier?

REMARKS:


Y

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4. CE TRANSISTOR AMPLIFIER

AIM: To find the frequency response of a common emitter amplifier and to find the bandwidth, voltage

gain, and output impedance.


REQUIRED

1 TRANSISTOR BC 107 1

2 BREAD BOARD WB 102 1

3 T.P.S (0-30V)/1A 1


5 RESISTORS 1KΩ, 1

2.2KΩ, 1

10KΩ, 1

470Ω 1

6 CAPACITORS 10µF, 2

47µF 1

7 SIGNAL GENERATOR (0-1MHz) 1

8 CRO 20MHz 1

THEORY :

The circuit shows a common-emitter amplifier using NPN transistor. It may be noted from this circuit that

the input a.c. signal is applied across the base-emitter terminals and the output signal is taken across the collector

and emitter terminals. The emitter-base junction of a transistor is forward-biased by the VBB

supply. The collector-

base junction is reverse-biased by the Vcc

supply. The Vcc

supply along with the resistances RB and R

C determines

the Q- point. The capacitors C1 and C

2 are called blocking capacitors (or) coupling capacitors. Each capacitor

acts like a switch, which is open to a direct current but shorted to an alternating current. Because of this,

blocking capacitor blocks the direct current, but passes the alternating current. This action isolates d.c. bias

from an a.c. signal in the circuit. The function of capacitor C1 is to connect the a.c. signal source to the input

circuit (or base- emitter circuit) of the amplifier. The function of capacitor C2 is to connect the amplifier to its

load resistance or to the next stage of the amplifier. All the voltages and currents of the transistor are indicated

by the instantaneous total values (i.e., d.c. + a.c). Thus the relation gives the instantaneous value of the total

base current iB =I

B +i

b

The instantaneous value of the total collector currents is given by iC = I

C +i

C

Similarly, the instantaneous value of the total base to emitter voltage is given by

VBE

= VBE

+Vbe

and the instantaneous value of the total collector -to- emitter voltage is given by VCE

= VCE

+ Vce

Part -B

Exp. No.

Date:

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Here the upper case letters I and V indicate the d.c. (or quiescent-operating) current and voltage values

respectively. The lower case letter i and v represent the a.c. current and voltage values respectively. It may be

noted that the emitter terminal of a transistor is shown grounded, therefore common emitter amplifier is also

known as grounded emitter amplifier.

Common emitter amplifier parameters :

This circuit is used to determine amplifier parameters such as input resistance (Ri), output resistance

(RO), current gain (A

i), voltage gain (A

V) and power gain (A

P). Here it may be noted from the figure that r

be1

represents the ac resistance of the emitter-base junction as seen by the input signal. It is known as input resistance,

looking directly into the base and is designated by Ri (or) R

in (base). Here b is common emitter d.c current gain

(or hfe) of a transistor. The input resistance, (R

i) does not include the effect of external biasing resistors connected

to the base.

Another important point is that since βr'eis much smaller than resistance R

B, a major part of source

current passes through β.r1

e and a negligible part through the resistance R

B.

The following are the parameters of C E amplifier :-

1. Input resistance: -

It is the resistance looking directly into the base and is given by the ratio of base voltage to base

current. Thus input resistance is

Ri =V

b /i

b = V

in /i

b since V

in = β.r'

e.i

b

Ri = (β.r'e.ib)/ib = β.r'e

And the input resistance of the amplifier stage

Ris = R

B /(β.r'

e)

Therefore RB >>βr'

e

Therefore Ris =β.r'

e=R

i

2. Output resistance: -

It is the resistance looking into collector, and is approximately equal to the collector resistance (RC).

Mathematically the output resistance is

RO

=RC

3. Current gain: -

Ai = i

c / i

b = β

4. Voltage gain: - It is the ratio of output voltage (VO) to the input voltage (V

in ) Since the output voltage is the

same as collector voltage and input voltage is the same as base voltage, it is also known as voltage gain from

base to collector.

Av = V

O /V

in

We also know that Vin = i

b. β.r1

e and V

o = i

e R

C = β.i

b.R

C

Therefore Voltage gain Av =(β.i

b.R

C) / (i

b. β. r1

e )= R

C / r1

e

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5. Power gain: -

It is the product of current gain (Ai) and voltage gain (A

v).

AP = A

i.A

v = β(R

C / r1

e)

Characteristics and uses of common emitter amplifier: -

1. Its input resistance is in the range of 1k Ω to 2 k Ω, which is considered to be moderately low.

2. Its output resistance is about 50k Ω, and is very large.

3. Its current gain is very high and is in the range of 50 to 300.

4. Its voltage gain is of the order of 1500

5. Its power gain is very large i.e, in the order of 10,000 (equal to 40dB).

6. It produces phase reversal of the input signal i.e; output is 180o out of phase with respect to the input signal.

DESIGN: -

Choose VCC

= 9V VRe

= VCC

/10

VBE

= 0.7V VRe

= Ie R

e

IC

= 2mA Ie = V

Re /R

e

RC = 2.2K ( I

e ≈ I

c )

Re = 470 Ω

hfe =

Therefore β = 1+ hfe

IB = I

c / β =

RB = β.R

e /10 (or) R

B = 0.1. β.R

e

VBB

= IB.R

B +V

BE + I

eR

e

Therefore VBB

= (VCC

.R2) /(R

1+R

2)

RB = (R

1.R

2)/(R

1+R

2)

R1 = (V

CC.R

B)/V

BB

R2 =(R

1R

B)/(R

1- R

B)

For CE choose such that its reactance <<Re at 100Hz

XCE

≅ 0.1 Re

XCE

=1/2πf CE

CE = 1/2πfx

CE

Use C

E = 47µF

CC = 1/2πX

CE X

RB

Use CC = 10µF ≅ C

C1 = C

C2 = C

C = 10µF

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B

C

E

20mV(P-P) R

L

= 1 0 k Ω

R1

Ci= 10µF

C0= 10µF

C E = 4 7 µ FR

2

R E

= 4 7 0 Ω

R C

= 2 . 2

k Ω

Vcc

= 12V

Ri = 1k Ω

Vout

S.No

CIRCUIT DIAGRAM:

TABLE:

Input AC Voltage (Vi) =

Input frequency (f) Vout

(Volts) GAIN(AV) = V

out /V

idB=20log 10 A

V

PROCEDURE:

1. The circuit is connected as shown in the figure.4.1

2. Set Vs at 20mV (p-p), using the signal generator.3. Keeping the input voltage constant, vary the frequency from 0-1MHz in regular steps and note down the

corresponding output voltage.

4. Plot the graph between gain (dB) and frequency (Hz).

5. Find the output impedance

Output impedance: -

(a) Ri is removed from the circuit and then 20mV/1KHz signal is applied at the input Note down the

amplitude of the output signal.

fig 4.1

Table 4.1

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(b) Now a DRB is connected across the output terminal and DRB is adjusted such that the output voltage

is reduced to half of its maximum value.

6. Calculate the bandwidth from the graph.

MODEL GRAPH: -

RESULT: -

VIVA QUESTIONS : -

1. What is the main advantage of CE configuration over CB configuration as far as biasing is concerned?

2. What happens to the input impedance of the CE amplifier if CE is removed?

3. What is the phase-relationship between the input and output voltages of (1) CE amplifier (2) CC amplifier.

4. Compare all the parameters between CE and CC amplifier.

REMARKS:


Y

Frequency

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5. RC PHASE SHIFT OSCILLATOR

AIM: To design, construct and test a RC phase shift oscillator circuit and to measure its designed

frequency (f o).

EQUIPMENT AND COMPONENTS REQUIRED:

S.N0 EQUIPMENT/COMPONENT SPECIFICATION QUANTITY

REQUIRED

1. TRANSISTOR BC107 1

2. T.P.S UNIT 0- 30V 1

3. CRO 20 MHz 1

4. CAPACITORS (CC,C,C,C,C

E) 10µf 1

0.1µf 3

47µf 1

5. RESISTORS (R1, R2, R) 1k Ω 1

470Ω 1

THEORY:

RC phase shift oscillator is an audio frequency or low frequency oscillator. It uses a CE amplifier

whose output is given to three RC networks. The phase shift produced by the CE amplifier is 1800. Since an

oscillator requires a phase shift of 00 or 3600,the additional 1800 phase shift is obtained using three RC networks

with an individual shift of 600 each.

CIRCUIT OPERATION:

The circuit starts oscillating if there is any inherent noise in the transistor or any variations in the power

source. With this input at the base, the amplifier produces a collector current. The voltage at the collector is

amplified and shifted by 180o and this is fed to the RC Network which shifts the phase by180o and Feeds the

signal is in phase with the base current this increase the base current and so the collector current I C also

increases. This is again fed to base through the RC Network is inphase and so base current IB

further increases.

this process is contionuously to vary Icbetween its saturation and cutoff values resulting in oscillations.

Theoretical frequency Calculations

f=1/2πRC √6+4k K=RC / R

Exp. No.

Date:

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C.R.OCL 100

R1

R2

R R

R

RC

1kΩ C

C

10uF

C C C

RE 47uF

VCC = 12V

CE 470Ω

0.1µf 0.1µf 0.1µf

BC107

CIRCUIT DIAGRAM:

TABLE:

THEORETICAL PRACTICAL R C

FREQUENCY (KHz) FREQUENCY (KHz) (Ω) (µF)

PROCEDURE:

1. The connections are made as per the circuit diagram

2. Switch on the power supply.

3. Connect the C.R.O at the output of the circuit.

4. Adjust the potentiometer for distortion free waveforms.

5. Measure the output frequency and amplitude in CRO

6. Compare the theoretical and practical values of frequency.

7. Repeat the procedure for different resistance values.

8. Plot the graph for amplitude versus frequency.

fig 5.1

Table 5.1

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MODEL GRAPH:

V

Time (t)

RESULT:

VIVA QUESTIONS:

1. What is the purpose of RC Phase shift network?

2. List the applications of RC phase shift network.

3. What is the range of frequencies generated by RC phase shift network?4. What is the phase shift offered by each RC Section of the network?

REMARKS:


Y

0

T

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6. CLASS ‘A’

POWER AMPLIFIER

AIM:

To obtain the frequency response of Class ‘A’ power amplifiers.

APPARATUS:1. Class – 'A' power amplifier trainer kit.

2. Function generator (1 to10MHz)

3. C.R.O (0 to 30MHz)

4. Connecting wires

5. Multimeter.

CIRCIIT DIAGRAM:

R1

18kOhm_5%

R2

4.7kOhm_5%

R3

1.0kOhm_5%

R4470Ohm_5%

C1

22uF

C2

22uFQ1

BC107BP

Q2

BC107BP

R5

1.0kOhm_5%

R6

5.1kOhm_5%

R7

330Ohm_5%

C3

100uF

C4

100uF

T1 ..

R81.0kOhm_5%

12VVCC

V1

20mV

1000Hz

THEORY:

There are various classes of power amplifiers, including classes A,

AB, B and C. We shall be concerned here with the class ‘A’ linear power

amplifier. A class ‘A’ power amplifier is one whose emitter to base

remains forward biased during the entire input signal. If, in addition, the

output signal is an exact reproduction of the input, the amplifier is said to

be linear. A linear class’A’ power amplifier therefore does not distort or

change the shape of the signal waveform and delivers audio power to aload.

The circuit diagram of a power amplifier Q that receives its input

signal from a preamplifier or driver. R1 and R2 provide voltage divider

forward bias to Q. R3 is required for bias stabilization. And C1 is a

bypass capacitor for R3, to prevent degeneration of the audio signal.

Proper operation of this stage as a class A amplifier requires the bias to be

properly set so that an undistorted input signal delivered by the driver will

be amplified without distortion by Q.

C.R.O.

Exp. No.

Date:

Swarnandhra

7/23/2019 Bee Manual 2014


43

Test points include the bases, emitters, and collectors of Q1 and

Q2 and the secondary of output transformer T.Assume that the audio

amplifier is operating normally and a sine-wave test signal is coupled to

the input. The DC voltage measured at the bases Q1 and Q2 and emitters

should show that for these NPN transistors, each base is positive relative

to its emitter (for forward bias of the base –to emitter circuit). The DC

voltage at the collector of Q2 is approximately equal to Vcc, because of

the low primary resistance of T.

TABULAR FORM:

FREQUENCY

(In Hz)

INPUT VOLTAGE

(In Volts)

OUTPUT

VOLTAGE

(In Volts)

GAIN= 20 LOG

V0/VI (in dB)

MODEL GRAPH:

FREQUENCY (Hz)

G A I N (

d B

)

BAND

WIDTH

Swarnandhra

7/23/2019 Bee Manual 2014


CALCULATIONS :

Input power Pi = Vcc.Ic

Vcc = 12V

Ic = Collector current

Output power P0 = VI Where V & I r.m.s. Values of output voltage and current.

V = V0/2√ 2

I = IL (Multimeter indicates current in r.m.s.)

Efficiency η = (PO/Pi ) *100

PROCEDURE:

1.Switch ON the power supply.

2.Connect the signal generator to the input of the amplifier.

3.Select sine wave test signal of 1KHz and amplitude 20mV P-P and

observe the output waveforms at V1 and V2 using C.R.O.

4.calculate gain and plot the graph between gain and frequency.

RESULT: Thus obtained the frequency response of a Class ‘A’ Power amplifiers

and Plot the graph.

VIVA QUESTIONS:

1. What is the operation of Class – A, AB operations?

2. What is the efficiency of a Class –A and AB amplifiers?

3. What is the difference between the Class – A, Class – AB amplifiers?

4. What are the disadvantages of Class – A,AB amplifiers?

REMARKS:


Y

Bee Manual 2014

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