Download Lab Manual

1
EC010 307
PREPERAED BY
DEEPAK P.
APPROVED BY
HOD
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INDEX
Sl No
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
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19.
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Contents
INTRODUCTION
INSTRUCTION TO STUDENTS
LAB CYCLES
FAMILIARIZATION OF EQUIPMENTS
DIODES CHARACTERISTICS
ZENER DIODES CHARACTERISTICS
HALF WAVE RECTIFIERS
FULL WAVE RECTIFIERS
BDIDGE RECTIFIERS
CLIPPERS
CLAMPING
RC CIRCUITS
CHARACTERISTICS OF CE CONFIGURATION
CHARACTERISTICS OF CB CONFIGURATION
RC COUPLED CE AMPLIFIER
ZENER VOLTAGE REGULATOR
TRANSISTOR VOLTAGE REGULATOR
APPENDIX I (SYMBOLS, VARIABLES)
APPENDIX II(RATING OF TRANSISTOR)
APPENDIX III(COMPONENT VALUE IDENTIFICATION)
Page No
3
4
5
6
12
19
24
29
34
40
53
59
71
77
82
90
94
97
99
101
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INTRODUCTION
“A practical approach is probably the best approach to mastering a subject and gaining
a clear insight.”
Analog Circuits Practical session covers those practical oriented electronic circuits that are very
essential for the students to solidify their theoretical concepts. This workbook provides a
communication bridge between the theory and practical world of the electronic circuits. The
knowledge of these practical are very essential for the engineering students. All of these practical
are arranged on the modern electronic trainer boards.
This practical session comprises of two sections. The first section consists of Diode circuits.
Some of the very useful diode based circuits are discussed in this section. The second section
describes the Bipolar Junction Transistor based circuits. Different configurations of BJT
amplifier are discussed in this part of the book. Each and every practical provides a great in
depth practical concepts of BJT.
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INSTRUCTIONS TO THE STUDENTS
1. Write Experiment number , Experiment name, Experiment date in the rough record
2. Keep your rough record/ Fare record neat and clean.
3. Draw circuit diagram neatly with HB pencil in the rough record as per circuit given in the
lab manual/available in your laboratory.
4. Wire the circuit using electronic components available in the lab.
5. Write the readings in the observation table in the given format in the lab manual.
6. Draw waveforms in the given space.
7. Prepare for vive based on the experiment that you are going to do in a day.
8. The viva questions are included in the semester hand book as well as lab manual
9. Use text book, reference book or internet to find out answers of the questions.
10. Every student must complete your rough record get sign from the faculty on the same day
of your lab or the very next day itself.
11. Fare record must be completed and submitted in the next lab.
12. Keep the work place neat and clean.
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EC010 307 ANALOG CIRCUITS LAB
LAB CYCLES
Cycle 1
1. Familiarization of Equipments
2. Characteristics of Ordinary Diodes.
3. Characteristics of Zener diodes.
4. Half wave, Full wave and Bridge Rectifiers.
5. Clipping circuits.
6. Clamping circuits.
7. Frequency responses of RC circuits (RC Low pass and high pass filters, RC Integrating
and Differentiating circuits.)
Cycle 2
8. Zener Voltage Regulator
9. Characteristics of Transistors (CE & CB).
10. RC Coupled CE amplifier – frequency response characteristics.
11. Transistor Voltage regulator.
.
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EXPERIMENT NO. 1
FAMILIARIZATION OF EQUIPMENTS
AIM: To observe sine wave, square wave, triangular wave and ramp waveforms on the C.R.O.
and to measure amplitude and frequency of the waveforms.
Introduction:
a) D.S.O
Specification
Instek GDS-1052-U
50 MHz Digital Storage Oscilloscope
Brand:
Instek
Model No:
GDS-1052-U
Our Model No: GDS1052U
b) FUNCTION GENERATOR
This instrument is basically the frequency generator that can generate signals of different
frequency, amplitude and shape. It is known as variable frequency source.
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1.LED DISPLAY.
Displays internal or external frequency.
2. INTERNAUEXTERNAL SWITCH. PUSH IN : External Frequency Counter.
PUSH OUT:
Internal Frequency Counter.
3. RANGE SWITCHES.
Frequency range Selector.
4. FUNCTION SWITCHES.
Select Sine wave, Triangle wave or Square
wave output.
5. ATTENUATOR.
Selects Output Level by -20 dB.
6. GATE TIME INDICATOR.
Gate Time Is selected automatically by input
signal.
7. FREQUENCY DIAL.
Controls Output frequency in selected range.
8. MHz, KHz, Hz, mHz INDICATOR.
Indicates unit of frequency.
9. EXTERNAL COUNTER INPUT BNC.
Used as an External Frequency Counter.
10. SWEEP RATE CONTROL.
On/Off
Switch
for
Internal
Sweep
Generator, adjusts Sweep rate of Internal
Sweep Generator.
11. SWEEP WIDTH CONTROL.
Pull out and adjusts Magnitude of Sweep.
12. VCF INPUT BNC.
Voltage controlled Frequency Input permits
External Sweep. Frequency control sweep
rate control should be off when applying
External Voltage at this BNC.
13 SYMMETRY CONTROL.
Adjust Symmetry of Output Waveform
1:1to 10:1 with Push/Pull Switch On.
14. TTL/CMOS CONTROL.
Selects TTL or CMOS mode
15. TTL/CMOS OUTPUT BNC.
TTL/CMOS Level Output.
16. DC OFFSET CONTROLS.
Adds Positive or Negative DC Component
to Output Signal.
17. MAIN OUTPUT BNC.
Impedance 50 Ohm.
18. AMPLITUDE CONTROL.
Adjusts Output Level from 0 to 20 dB.
19. TILT STAND.
Pull Out to adjust tilt.
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20. POWER SWITCH.
Push type switch. turning on the power
when pressed.
21. FUSE HOLDER.
Replacing fuse with unscrewing
22. AC INLET.
For connection of the supplied AC power.
Procedure:
1. Connect function generator output at the input of C.R.O. at channel 1 or at channel 2
2. Select proper channel i.e. if signal is connected to channel 1 select CH1 and if signal is
connected to channel 2 select CH2
3. Adjust Time /Div knob to get sufficient time period displacement of the wave on the
CRO screen.
4. With fine tuning of time/Div make the waveform steady on screen.
5. Use triggering controls if waveform is not stable
6. Keep volt/div knob such that waveform is visible on the screen without clipping
7. Measure P-P reading along y-axis. This reading multiplied with volt/div gives peak to
peak amplitude of the ac i/p wave.
8. Measure horizontal division of one complete cycle. This division multiplied by time/div
gives time period of the i/p wave.
9. Calculate frequency using formula f = 1/T.
10. Note down your readings in the observation table
11. Draw waveforms of sine, square, ramp and triangular in the given space.
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Usually these are the shapes of the signal that can be generated using Function Generator.
WORKSHEET
Observation Table
Draw observed waveforms:
Sine wave: (Amplitude : ________ Frequency: _____________ )
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Square wave: (Amplitude : ________ Frequency: _____________ )
Triangular wave: (Amplitude : ________ Frequency: _____________ )
Ramp: ((Amplitude : ________ Frequency: _____________ )
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Conclusion:
Result
The DSO, Function Generator familiarization was done and the wave forms are noted.
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EXPERIMENT NO. 2
DIODE CHARACTERISTICS.
AIM: To obtain V-I characteristics of PN junction diode.
Introduction:
The semiconductor diode is formed by doping P-type impurity in one side and N-type of
impurity in another side of the semiconductor crystal forming a p-n junction as shown in the
following figure.
At the junction initially free charge carriers from both side recombine forming negatively
charged ions in P side of junction(an atom in P-side accept electron and becomes negatively
charged ion) and positively charged ion on n side(an atom in n-side accepts hole i.e. donates
electron and becomes positively charged ion)region. This region deplete of any type of free
charge carrier is called as depletion region. Further recombination of free carrier on both side is
prevented because of the depletion voltage generated due to charge carriers kept at distance by
depletion (acts as a sort of insulation) layer as shown dotted in the above figure.
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Working principle:
When voltage is not applied across the diode, depletion region forms as shown in the above
figure. When the voltage is applied between the two terminals of the diode (anode and cathode)
two possibilities arises depending on polarity of DC supply.
[1] Forward-Bias Condition: When the +Ve terminal of the battery is connected to P-type
material & -Ve terminal to N-type terminal as shown in the circuit diagram, the diode is said to
be forward biased. The application of forward bias voltage will force electrons in N-type and
holes in P-type material to recombine with the ions near boundary and to flow crossing junction.
This reduces width of depletion region. This further will result in increase in majority carriers
flow across the junction. If forward bias is further increased in magnitude the depletion region
width will continue to decrease, resulting in exponential rise in current as shown in ideal diode
characteristic curve.
[2]Reverse-biased: If the negative terminal of battery (DC power supply) is connected with Ptype terminal of diode and +Ve terminal of battery connected to N type then diode is said to be
reverse biased. In this condition the free charge carriers (i.e. electrons in N-type and holes in Ptype) will move away from junction widening depletion region width. The minority carriers (i.e.
–ve electrons in p-type and +ve holes in n-type) can cross the depletion region resulting in
minority carrier current flow called as reverse saturation current(Is). As no of minority carrier is
very small so the magnitude of Is is few microamperes. Ideally current in reverse bias is zero.
In short, current flows through diode in forward bias and does not flow through diode in reverse
bias. Diode can pass current only in one direction.
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Diode Characteristics Expressed as a Resistance
Experiment Procedure:
1. Connect the power supply, voltmeter, current meter with the diode as shown in the figure
for forward bias diode. You can use two multi meter (one to measure current through
diode and other to measure voltage across diode)
2. Increase voltage from the power supply from 0V to 20V in step as shown in the
observation table
3. Measure voltage across diode and current through diode. Note down readings in the
observation table.
4. Reverse DC power supply polarity for reverse bias
5. Repeat the above procedure for the different values of supply voltage for reverse bias
6. Draw VI characteristics for forward bias and reverse bias in one graph
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Circuit diagram (forward bias)
Circuit diagram (reverse bias)
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WORKSHEET
Observation table: (Forward bias)
Observation table: (Reverse bias)
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Draw V-I characteristics of PN junction diode:
Forward bias
Reverse bias
Conclusion:
Current through Silicon based diode starts increasingly exponentially when potential across
diode is approximately milli volts (Cut-in Voltage).
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A germanium diode requires a lower voltage due to its higher atomic number, which makes it
more unstable. Silicon is used far more extensively than germanium in solid state devices
because of its stability.
Important Viva Questions
1. List important specifications of the diode
2. What is breakdown voltage? What is the breakdown voltage of diode 1N4001 and
1N4007?
3. What is the highest forward current in the diode 1N4007?
4. List different types of the diode
5. List applications of the diode?
6. How to check diode with help of multimeter?
7. What is the reason for reverse saturation current ?
8. What is the forward voltage drop of silicon diode and germanium diode?
Result:
The diode characteristics were done and the wave forms are noted. The characteristics
curves are plotted.
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EXPERIMENT NO. 3
CHARACTERISTICS OF ZENER DIODES.
AIM: To obtain V-I characteristics of Zener diode.
Introduction:
The Zener diode is designed to operate in reverse breakdown region. Zener diode is used for
voltage regulation purpose. Zener diodes are designed for specific reverse breakdown voltage
called Zener breakdown voltage (VZ). The value of VZ depends on amount of doping.
Breakdown current is limited by power dissipation capacity of the zener diode. If power capacity
of the Zener is 1 W and Zener voltage is 10V, highest reverse current is 0.1A or 100 mA. If
current increases more than this limit, diode will be damaged. Forward characteristics of the
Zener diode is similar to normal PN junction diode.
Experiment Procedure:
1. Connect the power supply, voltmeter, current meter with the diode as shown in the figure
for reverse bias. You can use two multimeter (one to measure current through diode and
other to measure voltage across diode)
2. Increase voltage from the power supply from 0V to 20V in step as shown in the
observation table
3. Measure voltage across diode and current through diode. Note down readings in the
observation table.
4. Reverse DC power supply polarity for forward bias
5. Repeat the above procedure for the different values of supply voltage for reverse bias
6. Draw VI characteristics for reverse bias and forward bias in one graph
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Circuit diagram (reverse bias)
Circuit diagram (forward bias):
Model Graph
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WORKSHEET
Observation table: (Reverse bias)
Observation table: (Forward bias)
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Draw V-I characteristics of Zener diode:
Conclusion:
Important Viva Questions
1. What is the breakdown voltage of Zener diode used in your practical? What is the
power capacity. What is the maximum current that you can pass through it?
2. Can we operate normal PN junction diode in breakdown region for longer duration?
Give reason
3. What is the specialty of Zener diode so as we can operate it in breakdown region for
longer duration
4. What is the difference between Zener breakdown and Avalanche breakdown?
5. Draw Zener regulator circuit to obtain regulated DC voltage 6.8 V. Considering input
DC voltage in the range from 10V to 30V. Consider load resistance of 10KΩ.
6. Determine maximum and minimum value of Zener current if value of series
resistance is 1 K, load resistance is 2K and input varies from 10V to 30V. Zener
voltage is 5 V.
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7. Draw output waveform in the circuit of question 5, if we apply AC wave of 10V at
the input.
Result
The Zener diode characteristics were done and the wave forms are noted. The characteristics
curves are plotted.
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EXPERIMENT NO. 4
I.
HALF WAVE RECTIFIER
AIM: To observe waveform at the output of half wave rectifier with and without filter capacitor
and to measure DC voltage, DC current, ripple factor with and without filter capacitor
Introduction:
One of the very important applications of diode is in DC power supply as a rectifier to convert
AC into DC. DC Power supply is the important element of any electronic equipment. This is
because it provides power to energize all electronic circuits like oscillators, amplifiers and so on.
In electronic equipments, D.C. power supply is must. For example, we can’t think of television,
computer, radio, telephone, mobile as well as measuring instruments like CRO, multi-meter etc.
without DC power supply. The reliability and performance of the electronic system proper
design of power supply is necessary. The first block of DC power supply is rectifier. Rectifier
may be defined as an electronic device used to convert ac voltage or current into unidirectional
voltage or current. Essentially rectifier needs unidirectional device. Diode has unidirectional
property hence suitable for rectifier. Rectifier broadly divided into two categories: Half wave
rectifier and full wave rectifier. In this experiment, you will construct half wave rectifier.
Working principle of half wave rectifier:
In half wave rectifier only half cycle of applied AC voltage is used. Another half cycle of AC
voltage (negative cycle) is not used. Only one diode is used which conducts during positive
cycle. The circuit diagram of half wave rectifier without capacitor is shown in the following
figure. During positive half cycle of the input voltage anode of the diode is positive compared
with the cathode. Diode is in forward bias and current passes through the diode and positive
cycle develops across the load resistance RL. During negative half cycle of input voltage, anode
is negative with respected to cathode and diode is in reverse bias. No current passes through the
diode hence output voltage is zero.
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Half wave rectifier without filter capacitor convert AC voltage into pulsating DC voltage. Filter
capacitor is used to obtain smooth DC voltage. Construct following circuit to perform this
practical.
Practical Circuit diagram:
List of components:
1. Transformer Input : 230V AC, output : 12V AC, 500 mA
2. Diode 1N4007
3. Resistor 10K
4. Capacitor 1000μF
5. Toggle Switch
Experiment Procedure:
1. Construct circuit on the bread board.
2. Keep toggle switch OFF to perform practical of half wave rectifier without filter
capacitor and ON to connect filter capacitor.
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WORKSHEET
Waveforms:
Without filter capacitor:
Input Waveform at secondary of transformer
Output waveform:
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With filter capacitor:
Input Waveform at secondary of transformer:
Output waveform:
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Observations:
Without filter capacitor
1. AC Input voltage (rms) Vrms= ___________
2. DC output voltage VDC = ___________
3. DC current: IDC =______________
4. AC output voltage (Ripple voltage) Vr: __________
5. Ripple factor: (Vr/VDC) = ______________
With filter capacitor
1. AC Input voltage (rms) Vrms= ___________
2. DC output voltage VDC = ___________
3. DC current: IDC =______________
4. AC output voltage (Ripple voltage) Vr: __________
5. Ripple factor: (Vr/VDC) = ______________
Conclusion:
Important Viva Questions
1. Define ripple factor
2. What is the effect of load resistance on ripple voltage in presence of filter capacitor?
3. What is the effect of value of filter capacitor on ripple voltage?
4. What is the PIV necessary for the diode if transformer of 24V is used ?
5. What is the mathematical relationship between rms input AC voltage and DC output
voltage in half wave rectifier with and without filter capacitor?
Result
The Half wave rectifier circuit was done and the wave forms with and without filter capacitor are
noted. The DC voltage, DC current, ripple factor with and without filter capacitor is noted.
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EXPERIMENT NO. 5
II.
FULL WAVE RECTIFIER
AIM: To observe waveform at the output of full wave rectifier with and without filter capacitor.
To measure DC voltage, DC current, ripple factor with and without filter capacitor.
Introduction:
Full wave rectifier utilizes both the cycle of input AC voltage. Two or four diodes are used in
full wave rectifier. If full wave rectifier is designed using four diodes it is known as full wave
bridge rectifier. Full wave rectifier using two diodes without capacitor is shown in the following
figure. Center tapped transformer is used in this full wave rectifier. During the positive cycle
diode D1 conducts and it is available at the output. During negative cycle diode D1 remains OFF
but diode D2 is in forward bias hence it conducts and negative cycle is available as a positive
cycle at the output as shown in the following figure. Note that direction of current in the load
resistance is same during both the cycles hence output is only positive cycles.
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Advantages of full wave rectifier over half wave rectifier:
1. The rectification efficiency is double than half wave rectifier
2. Ripple factor is less and ripple frequency is double hence easy to filter out.
3. DC output voltage and current is higher hence output power is higher.
4. Better transformer utilization factor
5. There is no DC saturation of core in transformer because the DC currents in two halves of
secondary flow in opposite directions.
Disadvantages:
1. Requires center tap transformer
2. Requires two diodes compared to one diode in half wave rectifier.
Practical Circuit diagram:
List of components:
1. Transformer (center tapped) 12-0-12 V AC, 500 mA
2. Diode 1N4007 ---- 2 No.
3. Resistor 10K
4. Capacitor 1000μF
5. Toggle Switch
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Experiment Procedure:
1. Construct circuit on the general board.
2. Keep toggle switch OFF to perform practical of full wave rectifier without filter capacitor
and ON to connect filter capacitor.
WORKSHEET
Waveforms:
Without filter capacitor:
Input Waveform at secondary of transformer:
Output waveform:
32
With filter capacitor:
Input Waveform at secondary of transformer:
Output waveform:
33
Observations:
Without filter capacitor
1. AC Input voltage (rms) Vrms= ___________
2. DC output voltage VDC = ___________
3. DC current: IDC =______________
4. AC output voltage (Ripple voltage) Vr: __________
5.
Ripple factor: (Vr/VDC) = ______________
With filter capacitor
1. AC Input voltage (rms) Vrms= ___________
2. DC output voltage VDC = ___________
3. DC current: IDC =______________
4. AC output voltage (Ripple voltage) Vr: __________
5. Ripple factor: (Vr/VDC) = ______________
Conclusion:
Important Viva Questions
1. What is the frequency of AC component at the output of full wave rectifier? Give
reason.
2. What is the difference in DC output voltage in half wave and full wave rectifier for
the same AC input?
3. What is the PIV necessary for the diode if transformer of 24-0-24 V is used ?
4. What is the mathematical relationship between rms input AC voltage and DC output
voltage in half wave rectifier with and without filter capacitor?
Result
The Full wave rectifier circuit was done and the wave forms with and without filter capacitor are
noted. The DC voltage, DC current, ripple factor with and without filter capacitor is noted.
34
EXPERIMENT NO. 6
III.
BRIDGE RECTIFIER
AIM: To observe waveform at the output of bridge rectifier with and without filter capacitor. To
measure DC voltage, DC current, ripple factor with and without filter capacitor.
Introduction:
The Bridge rectifier is a circuit, which converts an ac voltage to dc voltage using both half cycles
of the input ac voltage. The Bridge rectifier circuit is shown in the following figure.
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The circuit has four diodes connected to form a bridge. The ac input voltage is applied to the
diagonally opposite ends of the bridge. The load resistance is connected between the other two
ends of the bridge. For the positive half cycle of the input ac voltage, diodes D1 and D2 conduct,
whereas diodes D3 and D4 remain in the OFF state. The conducting diodes will be in series with
the load resistance RL and hence the load current flows through RL. For the negative half cycle
of the input ac voltage, diodes D3 and D4 conduct whereas, D1 and D2 remain OFF. The
conducting diodes D3 and D4 will be in series with the load resistance RL and hence the current
flows through RL in the same direction as in the previous half cycle. Thus a bi-directional wave
is converted into a unidirectional wave.
The circuit diagram of the bridge rectifier with filter capacitor is shown in the following figure.
When capacitor charges during the first cycle, surge current flows because initially capacitor acts
like a short circuit. Thus, surge current is very large. If surge current exceeds rated current
capacity of the diode it can damage the diode. To limit surge current surge resistance is used in
series as shown in the figure. Similar surge resistance can be used in half wave as well as centertapped full wave rectifier also.
Bridge rectifier package (combination of four diodes in form of bridge) is easily available in the
market for various current capacities ranging from 500 mA to 30A. For laboratory purpose you
can use 1A package.
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Advantages of bridge rectifier:
1. No center tap is required in the transformer secondary hence transformer design is
simple.
2. If stepping up and stepping down not required than transformer can be eliminated. (In
SMPS used in TV and computer, 230V is directly applied to the input of bridge rectifier).
3. The PIV of the diode is half than in center tap full wave rectifier
4. Transformer utilization factor is higher than in center tapped full wave rectifier
5. Smaller size transformer required for given capacity because transformer is utilized
effectively during both AC cycles.
Disadvantages of bridge rectifier:
1. Requires Four diodes (But package is low cost)
2. Forward voltage drop across two diodes. This will reduce efficiency particularly when
low voltage (less than 5V) is required.
3. Load resistance and supply source have no common point which may be earthed.
Practical circuit diagram:
List of components:
1. Transformer 12 V AC, 500 mA
2. Diode 1N4007 ---- 4 No. or 1 A bridge rectifier package
3. Resistor 10K [4] Capacitor 1000μF [5] Toggle Switch
37
Experiment Procedure:
1.
Construct circuit on the bread board.
2.
Keep toggle switch OFF to perform practical of full wave rectifier without filter
capacitor and ON to connect filter capacitor.
WORKSHEET
Waveforms:
Without filter capacitor:
Input Waveform at secondary of transformer:
Output waveform:
38
With filter capacitor:
Input Waveform at secondary of transformer:
Output waveform:
Observations:
Without filter capacitor
1. AC Input voltage (rms) Vrms= ___________
2. DC output voltage VDC = ___________
3. DC current: IDC =______________
4. AC output voltage (Ripple voltage) Vr: __________
5. Ripple factor: (Vr/VDC) = ______________
39
With filter capacitor
1. AC Input voltage (rms) Vrms= ___________
2. DC output voltage VDC = ___________
3. DC current: IDC =______________
4. AC output voltage (Ripple voltage) Vr: __________
5. Ripple factor: (Vr/VDC) = ______________
Conclusion:
Important Viva Questions
1. What is the mathematical expression for ripple factor. What is the ripple factor of bridge
rectifier without filter capacitor?
2. What is the mathematical relationship between rms AC input and DC output from the
bridge rectifier with and without filter capacitor? If transformer of 24V is used, what is
the DC output voltage with and without filter capacitor?
3. What is the PIV necessary for the diode if transformer of 12-0-12 V is used ?
4. What is the efficiency of full wave bridge rectifier?
Result
The Bridge rectifier circuit was done and the wave forms with and without filter capacitor are
noted. The DC voltage, DC current, ripple factor with and without filter capacitor is noted.
40
EXPERIMENT NO. 7
CLIPPERS
AIM: To observe waveforms at the output of various clipper circuits.
Introduction:
Clipping circuit is used to select for transmission that part of an arbitrary waveform which lies
above or below some reference level. Clipping circuit “clips” some portion of the waveform.
Clipping circuit is also referred to as voltage limiters. Clamping circuit preserves shape of the
waveform while clipping circuit does not preserve shape of waveform. Clipping circuit uses
some reference level. Waveform above or below this reference level is clipped. Clipping circuits
are also known as voltage limiter or amplitude limiter or slicers. Some clipper circuits are
explained here.
Positive cycle clipper circuits:
Positive cycle clipper circuits are shown in the figure with series and shunt diode. Transfer
characteristics and output waveform for sinusoidal input is shown.
Circuit Diagram
For series
41
For series diode:
1. When vi(t)<0, Diode D is in ON condition, input waveform is available at the output.
2. When vi(t)>0, Diode D is in OFF condition, input waveform is not available at the output
and output remains zero.
For shunt diode:
1. When vi(t)<0, Diode D is in ON condition which bypass the signal to the ground and
hence input waveform is not available at the output.
2. When vi(t)>0, Diode D is in OFF condition and acts like a OFF switch, input waveform
is available at the output.
For negative cycle clipper, polarity of diode is reverse.
Series diode positive clipping with positive reference:
In the circuit shown in the following figure, DC reference voltage is used. This is useful of we do
not want to clip entire positive cycle but some portion of positive half cycle.
When vi(t)<VR, Diode D is in ON condition, input waveform is available at the output.
When vi(t)> VR, Diode D is in OFF condition, input waveform is not available at the output and
output remains zero. Thus portion of output cycle clips as shown in the waveform.
Series diode positive clipping with negative reference:
If want to clip entire positive half cycle along with some portion of the negative cycle then
negative DC reference can be used as shown in the following figure. In this case only some
portion of negative cycle passes to the output.
42
1. When vi(t)<-VR, Diode D is in ON condition, input waveform is available at the output.
2. When vi(t)> -VR, Diode D is in OFF condition, input waveform is not available at the
output and output remains constant equal to VR. Thus entire positive cycle and some
portion of negative cycle below –VR clips.
Series diode negative clipping with reference:
Negative clipping can be achieved by changing polarity of the diode. Negative clipper with
negative reference voltage is shown in the following figure. This will clip some portion of
negative cycle.
1. When vi(t)>-VR, Diode D is in ON condition, input waveform is available at the output.
2. When vi(t)< -VR, Diode D is in OFF condition, input waveform is not available at the
output and output voltage remains constant which is equal to –VR.
Shunt diode positive clipping with negative reference voltage:
Shunt diode positive clipping with negative reference voltage is as shown in the following
circuit. This will clip entire positive cycle and some portion of negative cycle as shown in the
waveform.
43
1. When vi(t)<-VR, Diode D is in OFF condition (open circuit) and input waveform is
available at the output.
2. When vi(t)> -VR, Diode D is in ON condition, input waveform is not available at the
output and negative voltage –VR is extended to the output. Output voltage remains
constant equal to VR. Thus entire positive cycle and some portion of negative cycle
below –VR clips.
Shunt diode negative clipping with negative reference:
Negative clipping with negative reference voltage can be achieved by reversing polarity of the
diode. Some portion of negative cycle clips.
1. When vi(t)>-VR, Diode D is in OFF condition (open circuit) and input waveform is
available at the output.
2. When vi(t) < -VR, Diode D is in ON condition, input waveform is not available at the
output and negative voltage –VR is extended to the output. Output voltage remains
44
constant equal to VR. Thus entire positive cycle and some portion of negative cycle
below –VR clips.
List of components:
Experiment Procedure:
1. Connect function generator with CRO. Set sine wave with 6V peak to peak. Ensure that
offset voltage is 0.
2. Connect the function generator at the input of the clipping circuit
3. Observe output waveforms on the CRO for different clipping circuits and draw output
waveforms.
WORKSHEET
Circuit 1:
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46
Circuit 2:
47
Circuit 3:
48
Circuit 4:
Waveforms:
Input Waveform:
Output waveform for circuit 1:
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Output waveform for circuit 2:
50
Output waveform for circuit 3:
Output waveform for circuit 4:
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Conclusion:
Important Viva Questions
1. What are the other names for the clippers?
2. Draw output waveform for the following circuits if sinusoidal signal of 6V peak-to-peak
with zero offset is applied at the input. Consider reference voltage VR = +2V
Consider Zener voltage 2.5V
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VR = -3V
Result
The performance of different clipper circuit is observed and their transfer characteristics
are obtained.
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EXPERIMENT NO. 8
CLAMPING
AIM: To observe waveforms at the output of clamper circuits
Introduction: Diodes are widely used in clipping and clamping circuits. Clamping circuits are
used to change DC level (average level) of the signal which adds or subtracts DC value with the
signal. In clamping, shape of waveform remains same only offset value (DC level) will change.
Positive clamping adds positive DC level in the signal while negative clamping adds negative
DC level in the signal. Capacitor is widely used in the clamping circuit. Typical clamping
waveforms for the sinusoidal signal is shown below for positive clamping and negative
clamping.
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Clamping circuit is used in video amplifier of television receiver to restore DC level of video
signal to preserve overall brightness of the scene. Clamping circuit is also used in offset control
of function generator. Zero offset means no DC value is added in the AC signal.
Circuit operation:
Typical circuit operation of the positive clamping and negative clamping is given below.
Positive clamping:
Consider that 4V peak to peak signal with zero offset is applied at the input of the clamping
circuit. On the first negative half cycle of the input signal, diode D turns ON because anode
voltage is greater than cathode voltage. Capacitor charges to the negative peak voltage let us say
-2V in our example. The value of R should be high so that it will not discharge the capacitance.
After completion of negative cycle, positive cycle starts and diode turns OFF. Capacitance
voltage is in series with the input voltage. As per the Kirchoff’s law output voltage will be
addition of input voltage and capacitance voltage. Input signal is positive swing of +2V and
capacitor voltage is +2V. Thus during the positive peak of the input voltage total output voltage
will be +4V. We can consider that during the positive cycle capacitor acts like a battery and adds
+2V in the input. Waveforms are drawn here considering ideal diode, no leakage in the
capacitance under ideal situations which will be different in practical situations.
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Negative clamping:
In a negative clamping circuit polarity of diode is reverse than in positive clamping. In our signal
input swings from -2V to +2V (peak to peak 4V). Diode turns ON during the positive cycle and
charge is stored in the capacitor. Capacitor will charge up to +2 V in our example. During the
negative cycle this voltage will be in series with the input voltage and gives total output -4V
during negative peak of the input signal.
List of components:
Experiment Procedure:
1. Connect function generator with CRO. Set sine wave with 4V peak to peak. Ensure that
offset voltage is 0.
2. Connect the function generator at the input of the clamping circuit
3. Observe output waveforms on the CRO for different clamping circuits and draw output
waveforms.
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WORKSHEET
Draw circuit diagrams (as per circuit available in the laboratory or circuit connected on
breadboard):
Waveforms:
Input Waveform:
Output waveform for circuit 1:
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Output waveform for circuit 2:
Conclusion:
Important Viva Questions
58
Draw output waveform for the following circuits if input of 4V peak-to-peak with zero offset is
applied.
Result
The performance of different clamper circuit is observed and their transfer characteristics
are obtained.
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EXPERIMENT NO. 9
RC CIRCUITS
AIM: To obtain the characteristics of RC circuits.
THEORY:
Electrical devices are controlled by switches which are closed to connect supply to the device, or
opened in order to disconnect the supply to the device. The switching operation will change the
current and voltage in the device. The purely resistive devices will allow instantaneous change in
current and voltage. An inductive device will not allow sudden change in current and capacitance
device will not allow sudden change in voltage. Hence when switching operation is performed in
inductive and capacitive devices, the current & voltage in device will take a certain time to
change from pre switching value to steady state value after switching. This phenomenon is
known as transient. The study of switching condition in the circuit is called transient analysis.
The state of the circuit from instant of switching to attainment of steady state is called transient
state. The time duration from the instant of switching till the steady state is called transient
period. The current & voltage of circuit elements during transient period is called transient
response.
FORMULA:
Time constant of RC circuit = RC
APPARATUS REQUIRED:
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PROCEDURE:
1. Connections are made as per the circuit diagram.
2. Before switching ON the power supply the switch S should be in off position
3. Now switch ON the power supply and change the switch to ON position.
4. The voltage is gradually increased and note down the reading of ammeter and voltmeter
for each time duration in RC.In RL circuit measure the Ammeter reading.
5. Tabulate the readings and draw the graph of Vc(t)Vs t
CIRCUIT DIAGRAM:
MODEL GRAPH:
Charging
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Discharging
Observation Table
Charging:
Discharging:
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The process whereby the form of a non sinusoidal signal is altered by transmission through a
linear network is called “linear wave shaping”. An ideal low pass circuit is one that allows all the
input frequencies below a frequency called cutoff frequency fc and attenuates all those above this
frequency. For practical low pass circuit (Fig.) cutoff is set to occur at a frequency where the
gain of the circuit falls by 3 dB from its maximum at very high frequencies the capacitive
reactance is very small, so the output is almost equal to the input and hence the gain is equal to 1.
Since circuit attenuates low frequency signals and allows high frequency signals with little or no
attenuation, it is called a high pass circuit.
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64
65
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Sample Readings
LPF
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HPF
68
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Conclusion:
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Important Viva Questions
Result
RC low pass and high pass circuits are designed, frequency response and response at different
time constants is observed.
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EXPERIMENT NO. 10
CHARACTERISTICS OF CE CONFIGURATION
AIM: To obtain common emitter characteristics of NPN transistor
Introduction:
Transistor is three terminal active device having terminals collector, base and emitter. Transistor
is widely used in amplifier, oscillator, electronic switch and so many other electronics circuits for
variety of applications. To understand operation of the transistor, we use three configurations
common emitter, common base and common collector. In this practical, we will understand
common emitter configuration. As the name suggest, emitter is common between input and
output. Input is applied to base and output is taken from collector.
We will obtain input characteristics and output characteristics of common emitter (CE)
configuration. We will connect variable DC power supply at VBB and VCC to obtain
characteristics. Input voltage in CE configuration is base-emitter voltage Vbe and input current is
base current Ib. Output voltage in CE configuration is collector to emitter voltage VCE and
output current is collector current Ic. We will use multi-meter to measure these voltages and
currents for different characteristics. Collector to emitter junction is reverse biased and base to
emitter junction is forward biased. The CE configuration is widely used in amplifier circuits
because it provides voltage gain as well as current gain. In CB configuration current gain is less
than unity. In CC configuration voltage gain is less than unity. Input resistance of CE
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configuration is less than CC configuration and more than CB configuration. Output resistance of
CE configuration is more than CC configuration and less than CB configuration.
WORKSHEET
Circuit setup for input characteristics
Experiment Procedure:
1. Connect circuit as shown in the circuit diagram for input characteristics
2. Connect variable power supply 0-30V at base circuit and collector circuit.
3. Keep Vcc fix at 0V (Or do not connect Vcc)
4. Increase VBB from 0V to 20V, note down readings of base current Ib and base to emitter
voltage Vbe in the observation table.
5. Repeat above procedure for Vcc = +5V and Vcc = +10V
6. Draw input characteristics curve. Plot Vbe on X axis and Ib on Y axis.
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Observation table
Transistor: __________
Input Characteristics
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Circuit setup for output characteristics
Experiment Procedure:
1. Connect circuit as shown in the circuit diagram for output characteristics
2. Connect variable power supply 0-30V at base circuit and collector circuit.
3. Keep base current fix (Initially 0)
4. Increase VCC from 0V to 30V, note down readings of collector current Ic and collector
to emitter voltage Vce in the observation table.
5. Repeat above procedure for base currents Ib = 5μA, 50 μA, 100 μA. Increase base current
by increasing VBB.
6. Draw output characteristics curve. Plot Vce on X axis and Ic on Y axis.
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Observation table:
Transistor: __________
Output Characteristics
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Conclusion
Important Viva Questions
1. How to check transistor with help of multimeter?
2. How to check type of transistor (NPN or PNP) with help of multimeter?
3. Define current gain of the transistor in CE configuration. What is the DC current gain you
obtain in this practical?
Result
CE Transistor configuration was set up, I/P and O/P characteristics were plotted.
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EXPERIMENT NO. 11
CHARACTERISTICS OF CB CONFIGURATION
AIM: To obtain common base characteristics of NPN transistor
Introduction:
In a common base configuration, base terminal is common between input and output. The output
is taken from collector and the input voltage is applied between emitter and base. The base is
grounded because it is common. To obtain output characteristics, we wil l measure collector
current for different value of collector to base voltage (VCB). Input current is emitter current Ie
and input voltage is Veb. To plot input characteristics we wi ll plot Veb versus Ie . Current gain
for CB configuration is less than unity. CB configuration is used in common base amplifier to
obtain voltage gain. Output impedance of common base configuration is very high. CB amplifier
is used in multi-stage amplifier where impedance matching is required between different stages.
Circuit diagram to obtain input characteristics:
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Circuit diagram to obtain output characteristics
WORKSHEET
Experiment Procedure to obtain input characteristics:
1. Connect circuit as shown in the circuit diagram for input characteristics
2. Connect variable power supply 0-30V (VEE) at emitter base circuit and another power
supply 0-30V at collector base circuit (Vcc).
3. Keep Vcc fix at 0V (Or do not connect Vcc)
4. Increase VEE from 0V to 20V, note down readings of emitter current Ie and emitter to
base voltage Veb in the observation table.
5. Repeat above procedure for Vcc = +5V and Vcc = +10V
6. Draw input characteristics curve. Plot Veb on X axis and Ie on Y axis.
Experiment Procedure to obtain output characteristics:
1. Connect circuit as shown in the circuit diagram for output characteristics
2. Connect variable power supply 0-30V at emitter circuit and collector circuit.
3. Keep emitter current fix (Initially 0)
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4. Increase VCC from 0V to 30V, note down readings of collector current Ic and collector
to base voltage Vcb in the observation table.
5. Repeat above procedure for base currents Ie = 1mA, 5 mA and 10mA. Increase emitter
current by increasing VEE.
6. Draw output characteristics curve. Plot Vcb on X axis and Ic on Y axis.
Observation table for input characteristics:
Transistor: __________
Input Characteristics
80
Observation table for output characteristics:
Transistor: __________
Output Characteristics
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Conclusion
Important Viva Questions
1. What is early effect? Have you observed early effect in your experiment?
2. Compare common base and common emitter configuration
3. Justify the statement: Common base amplifier is used as buffer
4. What is the value of phase shift between input and output signal in common base and
common emitter amplifier?
Result
CB Transistor configuration was set up, I/P and O/P characteristics were plotted.
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EXPERIMENT NO. 12
RC COUPLED CE AMPLIFIER
AIM: To observe input-output waveforms of common emitter (CE) amplifier. To measure gain
of amplifier at different frequencies and plot frequency response
Introduction:
Common emitter amplifier is used to amplify weak signal. It utilizes energy from DC power
supply to amplify input AC signal. Biasing of transistor is done to tie Q point at the middle of the
load line. In the circuit shown, voltage divider bias is formed using resistors 10K and 2.2K.
During positive cycle, forward bias of base-emitter junction increases and base current increases.
Q point moves in upward direction on load line and collector current increases β times than base
current. (β is current gain). Collector resistor drop Ic*Rc increases due to increase in collector
current Ic. This will reduce collector voltage. Thus during positive input cycle, we get negative
output cycle. When input is negative cycle, forward bias of base-emitter junction and base
current will reduce. Collector current reduces (Q point moves downside). Due to decrease in
collector current, collector resistance voltage drop IcRc reduces and collector voltage increases.
Change in collector voltage is much higher than applied base voltage because less base current
variation causes large collector current variation due to current gain B. This large collector
current further multiplied by collector resistance Rc which provides large voltage output. Thus
CE amplifier provides voltage gain and amplifies the input signal. Without emitter resistance
gain of amplifier is highest but it is not stable. Emitter resistance is used to provide stability. To
compensate effect of emitter resistance emitter bypass capacitor is used which provides AC
ground to the emitter. This will increase gain of amplifier.
CE amplifier does not provide constant voltage gain at all frequencies. Due to emitter bypass and
coupling capacitors reduces gain of amplifier at low frequency. Reactance of capacitor is high at
low frequency, hence emitter bypass capacitor does not provide perfect AC ground (Emitter
impedance is high). There is voltage drop across coupling capacitor at low frequency because of
high reactance at low frequencies. Gain of CE amplifier also reduces at very high frequency
because of stray capacitances. Audio frequency transistors like AC127, AC128 works for audio
frequency range. It does not provide large voltage gain for frequency greater than 20 KHz.
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Medium frequency transistors are BC147/BC148/BC547/BC548 provides voltage gain up to 500
KHz. High frequency transistors like BF194/BF594/BF200 provides gain at radio frequencies in
the MHz range.
If we apply large signal at the input of CE amplifier, transistor driven into saturation region
during positive peak and cut-off region during negative peak (Q point reaches to saturation and
cut-off points). Due to this clipping occurs in amplified signal. So we have to apply small signal
at the input and ensure that transistor operates in active region.
Circuit diagram
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Experimental procedure:
1. Connect function generator at the input of the amplifier circuit.
2. Set input voltage 10 mV and frequency 100 Hz.
3. Connect CRO at the output of the amplifier circuit.
4. Observe amplified signal and measure output voltage
5. Increase frequency from the function generator and repeat above step
6. Note down readings of output voltage in the observation table for frequency range from
100 Hz to 10 MHz
7. Calculate voltage gain for different frequencies and gain in dB. Plot frequency response.
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MODEL GRAPH
Observation table
Input voltage: Vi = 10 Mv
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Conclusion
1. Design and set up an ampli_er for the speci_cations: gain = -50, output voltage = 10 VPP
; fL = 50 Hz and calculate Zi.
2. Set up an RC coupled ampli_er and measure its input and output impedances
Measurement of input resistance
Method 1:
Connect a known resistor (say 1 k) in series between the signal generator and the input of the
circuit. Calculate the current though the resistor from the potential di_erence across it. Since this
current also ows into the circuit, input resistance can be measured taking the ratio of the voltage
at the right side of the resistor to the current.
Method 2: Connect a pot in series between the signal source and the input of the circuit. Adjust
the pot until the input voltage to the circuit is 50% of the signal generator voltage. Remove the
pot from the circuit and measure its resistance using a multimeter.
Measurement of output resistance
Method 1: Measure the open circuit output voltage. This is the Thevenin voltage. Output
resistance of the circuit is actually the Thevenin resistance in series with the Thevenin voltage.
Connect a known value resistor, say 1 k and measure the voltage across it. A reduction in the
output voltage can be observed. Calculate the current through the resistor. Since this current also
ows trough the Thevenin resistance, output resistance is the ratio of the di_erence in the output
voltage to the current.
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Method 2: Connect a pot at the output of the circuit. Adjust the pot until the voltage across it is
50% of the open circuit voltage. Remove the pot from the circuit and measure
its resistance using a multimeter.
3. Differentiate between ac and dc load lines?
4. Explain their importance in ampli_er analysis.
5. Why is the center point of the active region chosen for dc biasing?
6. What happens if extreme portions of the active region are chosen for dc biasing?
7. Draw the output characteristics of the ampli_er and mark the load-line on it. Also mark
8. the three regions of operation on the output characteristics.
9. Which are the di_erent forms of coupling used in multi-stage ampli_ers?
Important Viva Questions
1. What will be emitter current in the given circuit diagram in absence of input AC signal?
2. Draw DC load line of CE amplifier circuit. Show Q point on it.
3. Draw output waveform when inverted sine wave is applied at the CE amplifier circuit
4. What is bandwidth? What is the approximate bandwidth of CE amplifier that you have
used during your practical.
5. What is the effect on gain of amplifier if value of Rc increases?
6. What are the different biasing methods?
7. What happens if emitter bypass capacitor is removed from the circuit?
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Result
With CE:
1. Mid-band gain of the amplifier =: : : : : :
2. Bandwidth of the amplifier =: : : : : : Hz
Without CE:
1. Mid-band gain of the amplifier = : : : : : :
2. Bandwidth of the amplifier = : : : : : :Hz
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EXPERIMENT NO. 12
ZENER VOLTAGE REGULATOR
AIM
1. To study zener diode as voltage regulator
2. To calculate % line regulation
3. To calculate % load regulation
APPARATUS
Zener diode, Resistors, Power supply, Multi meter
CIRCUIT DIAGRAM
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THEORY
Zener diode is a PN junction diode specially designed to operate in the reverse biased mode. It is
acting as normal diode while forward biasing. It has a particular voltage known as break down
voltage, at which the diode break downs while reverse biased. In the case of normal diodes the
diode damages at the break down voltage. But Zener diode is specially designed to operate in the
reverse breakdown region. The basic principle of Zener diode is the Zener breakdown. When a
diode is heavily doped, it’s depletion region will be narrow. When a high reverse voltage is
applied across the junction, there will be very strong electric field at the junction. And the
electron hole pair generation takes place. Thus heavy current flows. This is known as Zener
break down. So a Zener diode, in a forward biased condition acts as a normal diode. In reverse
biased mode, after the break down of junction current through diode increases sharply. But the
voltage across it remains constant. This principle is used in voltage regulator using Zener diodes
The figure shows the zener voltage regulator, it consists of a current limiting resistor RS
connected in series with the input voltage Vs and zener diode is connected in parallel with the
load RL in reverse biased condition. The output voltage is always selected with a breakdown
voltage Vz of the diode
REGULATION WITH A VARYING INPUT VOLTAGE (LINE REGULATION):
It is defined as the change in regulated voltage with respect to variation in line voltage. It is
denoted by ‘LR’. In this, input voltage varies but load resistance remains constant hence, the load
current remains constant. As the input voltage increases, form equation (3) Is also varies
accordingly. Therefore, zener current Iz will increase. The extra voltage is dropped across the Rs.
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Since, increased Iz will still have a constant Vz and Vz is equal to Vout. The output voltage will
remain constant. If there is decrease in Vin, Iz decreases as load current remains constant and
voltage drop across Rs is reduced. But eve n though Iz may change, Vz remains constant hence,
output voltage remains constant.
REGULATION WITH THE VARYING LOAD (LOAD REGULATION)
It is defined as change in load voltage with respect to variations in load current. To calculate this
regulation, input voltage is constant and output voltage varies due to change in the load
resistance value. Consider output voltage is increased due to increasing in the load current. The
left side of the equation (4) is constant as input voltage Vin, IS and Rs is constant. Then as load
current changes, the zener current Iz will also change but in opposite way such that the sum of Iz
and IL will remain constant. Thus, the load current increases, the zener current decreases and
sum remain
constant. Form reverse bias characteristics even Iz changes, Vz remains same hence, and output
voltage remains fairly constant.
PROCEDURE
A) Line Regulation:
1. Make the connections as shown in figure below.
2. Keep load resistance fixed value; vary DC input voltage from 5V to 15V.
3. Note down output voltage as a load voltage with high line voltage ‘VHL’ and as a load voltage
with low line voltage ‘VLL’.
4. Using formula, % Line Regulation = (VHL-VLL)/ VNOM x100, where VNOM = the nominal
load voltage under the typical operating conditions. For ex. VNOM = 9.5 ± 4.5 V
B) Load Regulation:
1. For finding load regulation, make connections as shown in figure below.
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2. Keep input voltage constant say 10V, vary load resistance value
3. Note down no load voltage ‘VNL’ for maximum load resistance value and full load voltage
‘VFL’ for minimum load resistance value.
4. Calculate load regulation using, % load regulation = (VNL-VFL)/ VFL x100
OBSERVATION TABLE
Calculations
% Line Regulation = (VHL-VLL) / VNOM x100 = ------------%
%voltage regulation = (VNL-VFL)/VFLx100 =----------%
Result
Line regulation:
1. % of regulation =: : : : : :
Load regulation:
1. % of regulation =: : : : : :
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EXPERIMENT NO. 13
TRANSISTOT VOLTAGE REGULATOR
Aim: To study the performance of zener diode regulator with emitter follower output and to plot
line regulation and load regulation characteristics.
Components and Equipments required: Transistor, zener diode, resistor, rheostat, dc source,
voltmeter, ammeter and bread board.
Theory
The limitations of an ordinary zener diode regulator are, the changes in current owing through
the zener diode cause changes in output voltage, the maximum load current that can be supplied
is limited and large amount of power is wasted in zener diode and series resistance. These
defects are recti_ed in a zener regulator with emitter follower output. It is a circuit that combines
a zener regulator and an emitter follower. The dc output voltage of the emitter follower is V0 =
VZ + VBE. When input voltage changes, zener voltage remains the same and so does the output
voltage. In an ordinary zener regulator, if the load current IL required is in the order of amperes,
zener diode should also have the same current handling capacity. But in zener regulator with
emitter follower output, current owing through the zener is IL/β. Another advantage of this
circuit is low output impedance. The expression for the output voltage can also be expressed as
V_ = Vi�VCE. This means that when the input voltage increases, output remains constant by
dropping excess voltage across the transistor. The limitation of this circuit is that the output
voltage directly depends on the zener voltage. This is rectified in the series voltage regulator with
feedback using error amplifier.
Procedure
1. Set up the circuit on the bread board after identifying the component leads.
2. Verify the circuit using a multimeter.
3. Note down output voltage by varying the input voltage from 0 V to 30 V in steps of 1 V.
4. Plot line regulation characteristics with Vi along x-axis and V0 along y-axis.
5. Calculate percentage line regulation using the expression ΔV0/ΔVi.
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6. Keep the input voltage at 15 V and note down output voltage by varying load current
from 0 to 500 mA in equal steps using a rheostat. Plot load regulation characteristics with
IL along x-axis and V0along y-axis.
7. Measure the full load voltage VFL by adjusting the rheostat until ammeter reads 500 mA.
8. Remove the rheostat and measure the output voltage to get no-load voltage VNL.
9. Mark VNL and VFL on the load regulation characteristics and calculate load regulation
as per the equation, VR = (VNL – VFL/VNL)*100%.
Circuit Diagram
Design
Output requirements V0= 8:5 V, IL = 500 mA when input is in the range 15 ±5 V. Selection of
transistor Select the power transistor 2N3055. Details of 2N3055: type: Si-NPN. Application: AF
Power, Maximum ratings: VCB = 100 V, VCE = 60 V, VEB = 7 V, IC max = 15 A, P = 115 W,
Nominal ratings: VCE=4V,IC=4A,hFE=20to70.
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Selection of Zener diode
We know that, VZ = V0+ VBE. Since the required output voltage V0 = 8.5 V,
VZ = V0 + 0.6 V = 9.1 V. Select SZ9.1 zener diode.
Result
The performance of transistor regulator circuit is observed.
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APPENDIX – I
SYMBOLS
98
VARIABLES
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APPENDIX – II
MAXIMUM RATINGS OF COMMONLY USED TRANSISTORS
BC107
Specifications:
1. Type : Si – NPN
2. operating point temp : 65o to 200oC
3. IC(max) : 100mA
4. hfe (min) = 110 : 100
5. hfe (max) : 450
6. VCE (max) : 45V
7. Ptot(max) : 300mW
8. Category(typical use) : Audio, low power
9. Possible substitutes :BC182, BC547
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DIODE
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APPENDIX – III
COMPONENT VALUE IDENTIFICATION
RESISTOR VALUE IDENTIFICATION
102
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STANDARD CAPACITOR VALUES