Solid State Devices Lab Manual
Solid State Devices Lab Manual
Solid State Devices Lab Manual
Dept. of Electronics and Communication Engineering
[This laboratory manual will guide to perform the necessary experiments to meet the requirement of
MAKAUT syllabus for Solid State Devices Lab for 2nd year students. It also contains the supplementary
materials like data sheets etc of some useful components to be used throughout the course.]
TABLE OF CONTENTS
TABLE OF CONTENTS .............................................................................................................. 2
FORMAT ......................................................................................................................................... 5
MARK DISTRIBUTION .............................................................................................................. 5
EXPERIMENT ‐ 1 ............................................................................................................................... 7
To study V-I characteristics of the semiconductor diode and determine D.C & A.C resistance.
................................................................................................................................................... 19
EXPERIMENT ‐ 3 ............................................................................................................................. 28
V-I characteristic of an n-p-n or p-n-p transistor, DC biasing the transistor in common- emitter
configuration and determination of its operating point (i.e. various voltage and currents). ..... 28
EXPERIMENT ‐ 4 ............................................................................................................................. 35
Design and simulate JEET/MOSFET bias circuit and compare the results.............................. 35
EXPERIMENT ‐ 5 ............................................................................................................................. 39
Design and simulate BJT bias circuit and compare the results. ................................................ 39
EXPERIMENT ‐ 6 ............................................................................................................................. 46
Design Voltage Regulator For Given Value Of Regulated Voltage Using Zener Diode. ........ 48
EXPERIMENT ‐ 8 ............................................................................................................................. 50
To study and use of oscilloscope to view waveforms and measure its amplitude and frequency
................................................................................................................................................... 52
Solid State Devices Laboratory Manual
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FORMAT FOR RECORD WRITING
2. Put the page numbers on the top of the individual page, Date & experiment
no.
4. Put your full signature, roll no., sec. & group no. at bottom right corner of
5. Record should be very neat and clean and all the circuits and tables should
10. Use the record and internal pages one side rolling.
12. Diagram should be drown on left side with pencil rest of thing should
FORMAT
MARK DISTRIBUTION
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LIST OF EXPERIMENTS
EXPERIMENT ‐ 1
APPARATUS REQUIRED:
Sl. No. NAME SPECIFICATION QUANTITY
1 Fixed Resistors - 5
2 Semiconductor Diode - 1
3 Bipolar Junction Transistor(BJT) - 1
4 Electrolyte Capacitor - 1
5 Potentiometer - 1
6 Integrated Circuit (IC) - 1
7 Light Emitting Diode (LED) - 1
8 Digital Multimeter - 1
9 Breadboard - 1
THEORY:
Experiment involves testing of various electronic components and devices and knowing
about their behavior. Electronic components involve semiconductor diode, transistor,
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potentiometer, IC, capacitor, resistor, LED, breadboard and devices like digital
multimeter.
Digital Multimeter:
A multi meter is the most useful electronic instrument, which can measure three
Quantities, voltage (AC or DC), current (DC or AC) and resistance. It is used because of
the following reasons:
1. They eliminate interpretation errors.
2. Parallax errors are eliminated.
3. Power requirement is less.
4. They reduce human reading errors.
5. Cost is less.
Solid State Devices Laboratory Manual
Resistors:
The components that are specifically designed to have a certain amount of Resistances
are called resistors. The principle applications of resistor are to limit currents, divide
voltage, and in certain cases generate heat.
Fixed Resistors:
The fixed resis9tors are available with a large selection of resistance values. One
common resistor is the carbon composition type, which is made with a mixture of finely
ground carbon, insulating filler and a resin binder. Other types include carbon film, metal
film and wire wound.
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Resistor Colour Code:
Note 2: The physical size of a resistor is indicative of the power it can dissipate, not of its resistance.
Variable Resistors:
These are designed so that their resistance values can be changed easily. Two basic
uses of variable resistors are to divide voltage and to control current. The variable
resistor used to divide voltage is called potentiometer. The potentiometer is a three
Solid State Devices Laboratory Manual
terminal device-two fixed and one variable (middle one). Resistance is to be determined
between one fixed terminal and other variable terminal. If the resistances measured in
each of the cases are same, then it is said to be working.
Capacitor:
A capacitor is a component that stores electric energy blocks the flow of Direct current
and permits the flow of alternating current to a degree, depends upon its capacitance
and the current frequency.
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Semiconductor Diode:
A semiconductor diode is a two layer, one junction device which is formed by joining
one p-type and one n-type semiconductor material. When the positive terminal of the
supply is connected to p-side of the diode and negative terminal to that of n-side, the
diode is said to be forward biased. In this condition, the width of the depletion layer of
diode decreases which results decrease in resistance. So the forward resistance is very
low of the order of few ohms. Ideally it is zero. Similarly, when the negative terminal of
the supply is connected to the p-side and positive terminal to n-side the diode is said to
be reverse biased. In reverse biased condition, the width of the depletion layer
increases which results increase in resistance. Thus reverse resistance of the diode
very much high of the order of some mega ohms. Ideally, it is infinite. The fig in side
represents the symbol of the diode. The tip of the arrow is a small vertical line which
indicates n-side of the diode. And other side indicates p-side of the diode.
There are so many diodes series are available in the market. Example of commonly
used diodes are 1N4001 to 1N4007, 1N4146, 1N4148, BY127, BA159. Depending on
the application and type of diodes include Zener diodes, Tunnel diodes, Pin diodes,
Varactor or varicap diodes, Schottky diodes, Backward diodes.
Transistor:
It is a three terminal semiconductor device consisting of two p-n junctions formed by
sandwiching a thin layer of n-type semiconductor between two layers of p-type
Solid State Devices Laboratory Manual
Integrated Circuits:
An integrated circuit is one in which circuit components such as transistors, Diode,
resistors, capacitors etc. are automatically part of a small semiconductor chips.
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A LED will emit a colored light not because of it's package color as many people used to
believe, but because of the emitting wavelength. The wavelength that an LED will
produce depends on the material used to form the p-n junction
Breadboard:
Solid State Devices Laboratory Manual
PROCEDURES
1. Testing Of Fixed Resistor
The theoretical value of resistance and tolerance is found by proper numbering of color
bands present on them.
1. Beginning from color band which is nearer to the external lead and that color
must not be gold or silver.
2. The second band is the second digit.
3. The third band is the number of zeros following the second digit, or the
multiplier.
4. Fourth band indicates the tolerance and it is gold/silver.
5. For practical measurement of resistance value keep the multimeter knob at the
higher resistance position and if the display of the multimeter is showing point
values only then change the multimeter knob to its nearer low range position until
you are not getting a real value.
6. Percentage of error can be calculated using formula,
7. Percentage of error
2. Testing Of Potentiometer
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1. The terminals of the potentiometer are marked 1, 2, and 3 as shown in fig.
terminal 1 and 3 are fixed whereas terminal 2 is variable.
2. Touch two probes of multimeter to terminals 1&2, 2&3 and 1&3 respectively and
note down the readings.
3. Vary the knob, take four to five readings.
4. If the resistance between fixed terminals i.e. 1 and 3 are same to that of sum of
resistances between 1 & 2 and 2 & 3. Then it is working, otherwise faulty.
3. Testing of Capacitor
You can use your multimeter as an ohmmeter to test the capacitor.
1. Discharge the capacitor by shortening its leads. That is-use a wire and connect
the leads of the capacitor together. This will discharge it.
2. Put your multimeter in the high ranges 10K-1M
3. Connect multimeter to capacitor leads (observe the polarity if electrolytic). As
soon as the leads make contact, the meter will swing near zero. It will then move
slowly toward infinity. Finally the meter would come to be infinite ohms because
the capacitor is being charged by the battery of the multimeter.
4. If the capacitor is bad, it will go to zero ohms and remain there. This is called a
shortened capacitor
5. In the case of an open capacitor there will be no ohmmeter indication.
6. Some capacitors have a low dielectric leakage. You will know this if the
ohmmeter comes to rest at a point lower than infinite. Test a known good
capacitor of the same type to be sure.
2) Diode
SL. SPECIFICATION FORWARD BIAS REVERSE BIAS REMARK
NO. VOLTAGE VOLTAGE
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3) Transistor
SL. SPECIFICATION FORWARD BIAS REVERSE BIAS REMARK
NO. VOLTAGE VOLTAGE
VBE VBC VBE VBC
4) Capacitor
SPECIFICATION CHARGING DISCHARGING REMARK
CONDITION CONDITION
5) Potentiometer
SL. NO. SPECIFICATION R12 R23 R12+R23 R13 REMARK
6) IC
SPECIFICATION TOTAL PIN NO.
7) LED
FORWARD BIAS REVERSE BIAS COLOR REMARK
CONCLUSION:
*****Write in your own language what you learn from this experiment. *****
Solid State Devices Laboratory Manual
EXPERIMENT ‐ 2
APPARATUS REQUIRED:
Name of the
Sl. No. Specification Quantity
Apparatus
1 Diode IN4007 1
2 Potentiometer 1KΩ 1
3 Resistor 1KΩ 1
DC
4 Power supply 1
-12v to +12v
5 Multimeter Digital 1
6 Wire -- As per required
7 Breadboard - 1
THEORY:
Donor impurities (pentavalent) are introduced into one-side and acceptor impurities into
the other side of a single crystal of an intrinsic semiconductor to form a p-n diode with a
junction called depletion region (this region is depleted off the charge carriers). This
region gives rise to a potential barrier Vγ called Cut- in Voltage. This is the voltage
across the diode at which it starts conducting. The P-N junction can conduct beyond this
Potential.
The P-N junction supports unidirectional current flow. If +ve terminal of the input supply
is connected to anode (P-side) and –ve terminal of the input supply is connected to
cathode (N- side), then diode is said to be forward biased. In this condition the height of
the potential barrier at the junction is lowered by an amount equal to given forward
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biasing voltage. Both the holes from p-side and electrons from n-side cross the junction
simultaneously and constitute a forward current ( injected minority current – due to
holes crossing the junction and entering N-side of the diode, due to electrons crossing
the junction and entering P-side of the diode). Assuming current flowing through the
diode to be very large, the diode can be approximated as short-circuited switch. If –ve
terminal of the input supply is connected to anode (p-side) and +ve terminal of the input
supply is connected to cathode (n-side) then the diode is said to be reverse biased. In
this condition an amount equal to reverse biasing voltage increases the height of the
potential barrier at the junction. Both the holes on p-side and electrons on n-side tend to
move away from the junction thereby increasing the depleted region. However the
process cannot continue indefinitely, thus a small current called reverse saturation
current continues to flow in the diode. This small current is due to thermally generated
carriers. Assuming current flowing through the diode to be negligible, the diode can be
approximated as an open circuited switch.
It is observed that Ge diode has smaller cut-in-voltage when compared to Si diode. The
reverse saturation current in Ge diode is larger in magnitude when compared to silicon
diode.
Forward Resistance:
The resistance offered by the diode in the forward bias condition is known as forward
resistance. This resistance is of two types, they are,
D.C forward resistance
Solid State Devices Laboratory Manual
The ac forward resistance is more significant as the diodes are generally used with ac
supply. The ac forward resistance can be determined from the forward characteristics
as shown in fig.2. If P is the operating point at any instant, then forward voltage is OB
and forward current is OE. To find the ac forward resistance, vary the forward voltage
on both sides of the OP.
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Reverse Resistance:
The resistance offered by the diode in the reverse bias condition is known as reverse
resistance. It can be dc or ac reverse resistance depending upon whether the reverse
bias is direct or alternating voltage. Ideally, the reverse resistance of a diode is infinite.
However practically, the reverse resistance is not infinite, because for any value of
reverse bias, there exist a small leakage current. But reverse resistance is very large
than forward resistance.
has been seen that the current increases very slowly and the curve is non-linear.
It is because; the external applied voltage is used to overcome the potential
barrier.
3. Reverse Bias: With reverse bias to the p-n junction,i.e, p-type semiconductor is
connected to the negative terminal and n-type semiconductor is connected to the
positive terminal of the supply voltage, the potential barrier at the junction
increases. Therefore, the junction resistance becomes very high and practically
the flow of current through the circuit is ceased.
If the reverse voltage is increased continuously, the kinetic energy of the electrons may
become high. At this stage breakdown of the junction occurs and can be characterized
by a sudden fall of resistance at the barrier region.
CIRCUIT DIAGRAM:
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Forward Bias
Reverse Bias
PROCEDURE:
Forward Biased Condition:
1. Connect the PN Junction diode in forward bias i.e Anode is connected to positive
of the power supply and cathode is connected to negative of the power supply.
2. Use a Regulated power supply of range (0-12)V through a potentiometer of 1KΩ
and a series resistance of 1KΏ.
Solid State Devices Laboratory Manual
3. For various values of forward voltage (VD) note down the corresponding values of
forward current (ID).
PRECAUTIONS:
1. While doing the experiment do not exceed the ratings of the diode. This may
lead to damage of the diode.
2. Connect multimeter in correct polarities as shown in the circuit diagram.
3. Do not switch ON the power supply unless you have checked the circuit
connections as per the circuit diagram.
OBSERVATION:
RL=?
1
2
3
4
5
6
7
8
9
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10
11
12
13
GRAPH (INSTRUCTIONS):
1. Take a graph sheet and divide it into 4 equal parts. Mark origin at the center of
the graph sheet.
2. Now mark +ve x-axis as Vd
+ve y-axis as Id
3. Mark the readings tabulated for diode forward biased condition in first
Quadrant and diode reverse biased condition in third Quadrant.
RESULT:
Thus the VI characteristics of PN junction diode is verified
DC forward resistance = ………. Ω
AC forward resistance = ………. Ω
CONCLUSION:
*****Write in your own language what you learn from this experiment. *****
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EXPERIMENT ‐ 3
APPARATUS REQUIRED:
Sl. No Name of the component Specification Quantity
1 Multimeter Digital 1
2 Transistor BC547 1
NPN
3 Potentiometer 4.7KΩ 2
4 Resistor 1KΩ,100KΩ 2
5 D.C. Power supply 6v and 12V --
6 Connecting wires -- As Per Required
7 Bread board -- 1
THEORY:-
The transistor is a solid state device and is an essential ingredient of every electronic
circuit. This is analogous to vacuum triode. The main difference is that transistor is a
current device while vacuum triode is a voltage device. The advantages of transistors
over a vacuum triode are long life, high efficiency, light weight, smaller in size, smaller
power consumption etc.
Solid State Devices Laboratory Manual
Bipolar junction transistor is a three terminal, two junction device. A junction transistor is
simply a sandwich of one type of semiconductor material between two layers of the
other type. Accordingly, there are two types of transistors: P-N transistor and P-N-P
transistor. When a layer of n-type material is sandwiched between two layers of p-type
material, the transistor is known as p-n-p transistor.
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(COMMON EMITTER CIRCUIT)
Input Characteristics:
It is the curve between base current IB and base emitter voltage VBE at constant
collector-emitter voltage VCE .the input chartestics of a CE configuration can be
Solid State Devices Laboratory Manual
determined by the circuit shown in fig. keeping VCE constant, the base current IB for
various values of VBE was noted. Then the reading obtained was plotted on the graph,
taking IB along y-axis and VBE x-axis. This gives the input characteristics at VCE=3v as
shown in the fig. following a similar procedure, a family of input chaterstics can be
drawn. The following points may be noted form the chartetstics:-
1. The characteristics resembles that of a forward biased diode curve. This is
expected since the base-emitter section of transistors is a diode and it is forward
biased.
2. As compared to CB arrangements, IB increases less rapidly with VBE. Therefore,
input resistance of CE circuit is higher than that of CB circuit.
Output Characteristics:
It is the curve between collector current IC and collector emitter voltage VCE at constant
base current, IB . The output characteristic of a CE circuit can be drawn with the help of
the circuit shown in the fig. keeping the base current IB fixed at some value and collector
current IC for various values of VCE was noted. Then the readings were plotted on a
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graph, taking IC along y-axis and VCE along x-axis. This gives the output chaterstics at
IB=5μA. The following points may be noted:-
1. The collector current, IC varies with VCE, for VCE between 0 and 1v only. After
this, collector current becomes almost constant and independent of VCE. This
values of VCE up to which IC changes with VCE is called knee voltage. The
transistors are always operated in the region above knee voltage.
2. Above knee voltage, IC is almost constant. However with small increases in IC
with increasing VCE is caused by the collector depletion layer getting wider and
capturing a few more majority carries before electron hole c combinations occur
in the base area.
3. For any value of VCE above knee voltage, the IC is approximately equal to βIB.
Solid State Devices Laboratory Manual
PROCEDURE:
1. Make the circuit diagram as shown in fig.
2. Set both the potentiometer at 0v.
3. Now, for input chaterstics, set VCE=3v and fix it.
4. Vary VBE, slowly in the range of 0.1v to up to end position of the potentiometer.
5. Measure the corresponding values of base-emitter voltage VBE, voltage drop
across base resistor and find base current.
6. Plot the graph between IB and VBE.
7. Repeat the above procedure for VCE=4v.
8. Now for output characteristics set IB=5μA i.e. fix VBE at 0.5v.
9. Vary VCE slowly 1 to 12v.
10. Measure the corresponding values of collector-emitter voltage VCE, voltage drop
across collector resistor VRC and collector current IC.
11. Plot the graph between IC and VCE, at constant IB.
12. Repeat the above experiment for base current, IB=10μA.
OBSERVATIONS:
Reading for input:
1. At VCE=0V and RB=?
SL.NO VBE (V) VRB (V) IB=VRB/RB (μA)
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Reading for output:
1. At IB=10μA and RC=?
SL.NO VCE (V) VRC (V) IC=VRC/RC (ma)
CONCLUSION:
*****Write in your own language what you learn from this experiment. *****
Solid State Devices Laboratory Manual
EXPERIMENT ‐ 4
3. BREAD BOARD 01
4. DIGITAL MULTIMETER 01
Theory:
The Field Effect Transistor is a three terminal uni-polar semiconductor device that has
very similar characteristics to those of their Bipolar Transistor counterparts i.e., high efficiency,
instant operation, robust and cheap and can be used in most electronic circuit applications to
replace their equivalent bipolar junction transistors (BJT) cousins. Field effect transistors can be
made much smaller than an equivalent BJT transistor and along with their low power
consumption and power dissipation makes them ideal for use in integrated circuits such as the
CMOS range of digital logic chips. This is also true of FET's as there are also two basic
classifications of Field Effect Transistor, called the N-channel FET and the P-channel FET.
The Field Effect Transistor has one major advantage over its standard bipolar transistor cousins,
in that their input impedance, Rin is very high, (thousands of Ohms), while the BJT is
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comparatively low. This very high input impedance makes them very sensitive to input voltage
signals.
JFET ID Equation:
2
ID I VGS
DSS 1 V
P
Solid State Devices Laboratory Manual
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1 0
2 -0.25
3 -0.5
4 -0.75
5 -1.0
6 -1.25
7 -1.5
8 -1.75
9 -2.0
10 -2.25
11 -2.5
12 -2.75
Conclusion:
From the above experiment we have calculated the trans-conductance of the FET device
from its transfer characteristics curve and also checked the values of ID, IS and IG and concluded
that ID =IS and IG value is very small.
Solid State Devices Laboratory Manual
EXPERIMENT ‐ 5
Design and simulate BJT bias circuit and compare the results.
Apparatus Required:
330K,4.7K,68K,27K
2. RESISTORS 01-EACH
2.7K,33K,1.5K
3. BREAD BOARD 01
4. DIGITAL MULTIMETER 01
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BE7105 BASIC ELECTRONICS LABORATORY MANUAL
Theory:
Active or Linear Region Operation
At constant current, the voltage across the emitter–base junction VBE of a bipolar
transistor decreases 2 mV (silicon) and 1.8mV (germanium) for each 1 °C rise in temperature
(reference being 25 °C). By the Ebers–Moll model, if the base–emitter voltage VBE is held
constant and the temperature rises, the current through the base–emitter diode IB will
increase, and thus the collector current IC will also increase. Depending on the bias point, the
power dissipated in the transistor may also increase, which will further increase its
temperature and exacerbate the problem. This deleterious positive feedback results in thermal
runaway. There are several approaches to mitigate bipolar transistor thermal runaway. For
example,
Negative feedback can be built into the biasing circuit so that increased collector
current leads to decreased base current. Hence, the increasing collector current
throttles its source.
Heat sinks can be used that carry away extra heat and prevent the base–emitter
temperature from rising.
The transistor can be biased so that its collector is normally less than half of the power
supply voltage, which implies that collector–emitter power dissipation is at its
maximum value. Runaway is then impossible because increasing collector current
leads to a decrease in dissipated power; this notion is known as the half-voltage
principle.
There are different types of biasing circuits are available. Some are given below:
Fixed bias
Collector to base feedback bias
Emitter stabilized bias
Voltage divider bias
Fixed bias circuit:
This is called fixed bias, as it provides a fixed value of biasing current IB irrespective of the
collector current IC. Since the supply voltage VCC and the base emitter voltage VBE are
constants, the selection of a base resistor RB sets the level of base current for the operating
point. It is interesting to know that since the base current IB is controlled by the level of RB
and IC is related to IB by a constant β, the magnitude of IC is not a function of the resistor RC.
Changing RC to any level will not affect the level of IB or IC as long as we remain in the
active region of the device.
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BE7105 BASIC ELECTRONICS LABORATORY MANUAL
RB=1MΩ
RC=4.7kΩ
Q =2N3904
point, so less current will go through the resistor in the base. Less current through the base
means less current through the collector.
RB=330kΩ
RC=4.7kΩ
Q =2N3904
Base-Emitter Loop
From Kirchhoff’s voltage law
VCC – IC R C – I B R B – VBE 0
Where IB << IC
I' I I I
C C B C
Solving for IB
VCC VBE
IB
R B βR C
Collector-Emitter Loop
Applying Kirchoff’s voltage law
VCE IC R C – VCC 0
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BE7105 BASIC ELECTRONICS LABORATORY MANUAL
This is a very stable bias circuit. The currents and voltages are nearly independent of
any variations in .The idea is that the voltage divider maintains a very stable voltage at the
base of the transistor, and since the base current is many times smaller than the current
through the divider, the base voltage remains practically unchanged.
RB1=68kΩ
RB2=27kΩ
RC =3.3kΩ
RE =1.5kΩ
Q =2N3904
The resistor RE provides the negative feedback. Due to the fact that the base voltage remains
unchanged, the negative feedback works very effectively and any unwanted increment of the
current gain produces an almost equal negative feedback. The collector and emitter currents
change just a few, and the Q point remains practically stable. Analysis can be done in 2
methods
Exact analysis
Approximate analysis
Approximate Analysis:
Where IB << I1 and I1 I2
R B 2 VCC
VB
R B1 R B 2
Where βRE > 10RB2
VE
IE
RE
VE VB VBE
From Kirchhoff’s voltage law
VCE VCC I C R C I E R E
IE IC
VCE V CC I C (R C R E )
FIXED BIAS:
S 1
BASE BIAS:
1
S
RC
1
R B RC
1
S
RE
Conclusion: 1
From the above
R E RTH experiment we have concluded
that the stability factor of the voltage divider is less as compared to other biasing circuits. So,
voltage divider bias is the more stabled bias circuit.
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BE7105 BASIC ELECTRONICS LABORATORY MANUAL
EXPERIMENT ‐ 6
APPARATUS:
THEORY:
Under specific fabrication conditions, a diode may be created that will not be destroyed if
the breakdown voltage is exceeded, as long as the current does not exceed a defined
maximum (to prevent overheating). These devices are known as zener diodes and they are
designed to have an avalanche characteristic that is very steep.
In the forward bias region, the zener behaves like a regular diode within specified current
and/or power limits. The magic of these devices comes in when we get into the reverse bias
region. As previously mentioned, the zener is designed to have an almost vertical avalanche
characteristic at the breakdown voltage – hereinafter also called the zener voltage, and it is
ideal for use in voltage regulation. The limiting (maximum) power for a zener diode is given
by Pz=Vz*Izmax and is a function of the design and construction of the diode. The knee of
the curve (the current for which |vD|=VZ) is generally approximated as 10% of Izmax, or
Izmin=0.1Izmax.
There are two distinctly different mechanisms that may cause breakdown in a zener diode:
1. Above approximately eight (8) volts, the predominant mechanism is avalanche
breakdown, also referred to as impact ionization or avalanche multiplication. This process
begins with thermally generated minority carriers that acquire enough kinetic energy to break
covalent bonds and create an EHP through collisions with crystal atoms. The free carriers
created through this collision contribute to the reverse current and may also possess enough
energy to participate in collisions, creating further EHPs and the avalanche effect.
2. The high field emission or zener breakdown mechanism is the second method of disrupting
the covalent bonds of the crystal and increasing the reverse bias diode current. The reverse
voltage where this occurs is determined by the diode doping and occurs when the depletion
layer field is large enough to break covalent bonds and cause the number of free carriers due
to EHP generation to multiply.
Either of these effects, or a combination of the two, significantly increases the current in
the reverse bias region while having a negligible effect in the voltage drop across the
junction. Although “breakdown” and “disruption” and words of that order have been liberally
used in the previous discussion, please realize that the zener process in not inherently
destructive unless the maximum power dissipation specified for the device is exceeded.
CIRCUIT DIAGRAM:
OBSERVATION TABLE
Sr. Input voltage Output voltage Voltage across zener Current through
no diode zener diode
CONCLUSION:
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BE7105 BASIC ELECTRONICS LABORATORY MANUAL
EXPERIMENT ‐ 7
APPARATUS:
THEORY:
This ability to control itself can be used to great effect to regulate or stabilize a voltage source
against supply or load variations. The fact that the voltage across the diode in the breakdown
region is almost constant turns out to be an important application of the zener diode as a
voltage regulator
As mentioned earlier, the characteristics of the zener diode make it ideal for application as a
voltage regulator. Placing the zener diode in parallel with the load as shown in Figure -6.1
(reproduced to the right) ensures an essentially constant output voltage even source voltage
may vary. The key to the design of this voltage regulator is to choose the resistor Ri to keep
the zener diode in the breakdown region, while ensuring that the diode current never exceeds
Izmax.
Now we derive the expression for this circuit parameter by developing the nodal expression
for the zener current and defining the two extremes for iZ in terms of the input/output
conditions:
1. Izmin occurs when the load current is maximum and the source voltage is minimum.
2. Izmax occurs when the load current is minimum and the source voltage is maximum.
CIRCUIT DIAGRAM
PROCEDURE:
OBSERVATION TABLE :
CONCLUSION:
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EXPERIMENT ‐ 8
APPARATUS:
THEORY:
An LDR is a component that has a resistance that changes with the light intensity that falls
upon it. They have a resistance that falls with an increase in the light intensity falling upon
the device.
You can therefore see that there is a large variation between these figures. If you plotted this
variation on a graph you would get something similar to that shown by the graph to the right.
APPLICATIONS
There are many applications for Light Dependent Resistors. These include:
1) Lighting switch
The most obvious application for an LDR is to automatically turn on a light at certain
light level. An example of this could be a street light.
CIRCUIT DIAGRAM:
PROCEDURE:
OBSERVATION TABLE:
CONCLUSION:
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BE7105 BASIC ELECTRONICS LABORATORY MANUAL
EXPERIMENT ‐ 9
APPARATUS REQUIRED:
S.L. NO NAME OF THE SPECIFICATION QUANTITY
EQUIMENT
1 SCINETIFIC 01
CATHODE RAY SM203G
OSILOSCOPE (CRO) 30 MHZ
2 SCINETIFIC 01
FUNCTION GENERATOR SM5071
3 MHZ
3 BNC PROBE 01
THEORY:
The Cathode-Ray Oscilloscope (CRO) is a common laboratory instrument that
provides accurate time and amplitude measurements of voltage signals over a wide
range of frequencies. Its reliability, stability, and ease of operation make it suitable as
a general purpose laboratory instrument.
The cathode ray is a beam of electrons which are emitted by the heated cathode
(negative electrode) and accelerated toward the fluorescent screen. The assembly of
the cathode, intensity grid, focus grid, and accelerating anode (positive electrode) is
called an electron gun. Its purpose is to generate the electron beam and control its
intensity and focus. Between the electron gun and the fluorescent screen are two
pair of metal plates - one oriented to provide horizontal deflection of the beam and
one pair oriented ot give vertical deflection to the beam. These plates are thus
referred to as the horizontal and vertical deflection plates. The combination of these
two deflections allows the beam to reach any portion of the fluorescent screen.
Wherever the electron beam hits the screen, the phosphor is excited and light is
emitted from that point. This conversion of electron energy into light allows us to
write with points or lines of light on an otherwise darkened screen.
In the most common use of the oscilloscope the signal to be studied is first amplified
and then applied to the vertical (deflection) plates to deflect the beam vertically and
at the same time a voltage that increases linearly with time is applied to the
horizontal (deflection) plates thus causing the beam to be deflected horizontally at a
uniform (constant> rate. The signal applied to the vertical plates is thus displayed on
the screen as a function of time. The horizontal axis serves as a uniform time scale.
CRO Operation:
A simplified block diagram of a typical oscilloscope is shown .In general, the
instrument is operated in the following manner. The signal to be displayed is
amplified by the vertical amplifier and applied to the verical deflection plates of the
CRT. A portion of the signal in the vertical amplifier is applied to the sweep trigger as
a triggering signal. The sweep trigger then generates a pulse coincident with a
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COOCH BEHAR GOVERNMENT ENGINEERING COLLEGE
BE7105 BASIC ELECTRONICS LABORATORY MANUAL
selected point in the cycle of the triggering signal. This pulse turns on the sweep
generator, initiating the saw tooth wave form. The saw tooth wave is amplified by the
horizontal amplifier and applied to the horizontal deflection plates. Usually, additional
provisions signal are made for applying an external triggering signal or utilizing the
60 Hz line for triggering. Also the sweep generator may be bypassed and an external
signal applied directly to the horizontal amplifier.
CRO Controls:
The controls available on most oscilloscopes provide a wide range of operating
conditions and thus make the instrument especially versatile. Since many of these
controls are common to most oscilloscopes a brief description of them follows.
Cathode-Ray Tube:
1. Power and Scale Illumination: Turns instrument on and controls
illumination of the graticule.
2. Focus: Focus the spot or trace on the screen.
3. Intensity: Regulates the brightness of the spot or trace.
Horizontal-Sweep Section:
1. Sweep time/cm: Selects desired sweep rate from calibrated steps or admits
external signal to horizontal amplifier.
2. Sweep time/cm Variable: Provides continuously variable sweep rates.
Calibrated position is fully clockwise.
3. Position: Controls horizontal position of trace on screen.
4. Horizontal Variable: Controls the attenuation (reduction) of signal applied to
horizontal amplifier through Ext. Horizontal connector.
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BE7105 BASIC ELECTRONICS LABORATORY MANUAL
Trigger:
The trigger selects the timing of the beginning of the horizontal sweep.
1. Slope: Selects whether triggering occurs on an increasing (+) or decreasing
(-) portion of trigger signal.
2. Coupling: Selects whether triggering occurs at a specific dc or ac level.
3. Source: Selects the source of the triggering signal.
INT - (internal) - from signal on vertical amplifier
EXT - (external) - from an external signal inserted at the EXT. TRIG. INPUT.
LINE - 60 cycle trigger
4. Level: Selects the voltage point on the triggering signal at which sweep is
triggered. It also allows automatic (auto) triggering of allows sweep to run free
(free run).
PROCEDURE:
1. First of all set all the Equipment according to the experiment.
2. Connect the CRO with Function generator through BNC cord(Black probe to
Black probe and red to red Probe)
3. For operating ch-1 choose the Channel-1 knob in the front panel of the CRO
for ch-2 choose the channel-2 knob
4. There are three types of waveform according to our need we set the
waveform
5. First adjust the function generator with a frequency as given with a type of
signal like square, triangular, Sinusoidal.
6. Trace the waveform by using tracing paper and observe the no of horizontal
division, no of vertical division, time/div, volts/div.
7. Take different frequency and observe.
8. Calculate the percentage of error of frequency by using the formula
Percentage of error =
TABULATION:
No. of No. of Practical
Sl. Waveform Theoretical Vertical Volt/Div Vpp Horizontal Time/Div Time Frequency % of
No. Frequency Division Division Period (F) Error
(T)
1 Sine wave
2 Square
wave
3 Triangular
Wave
4 Sine wave
5 Square
wave
6 Triangular
Wave
7 Sine wave
8 Square
wave
9 Triangular
Wave
CONCLUSION:
*****Write in your own language what you learn from this experiment. *****