Analog Circuits Lab
Exp No: 1
Date :
FAMILIARISATION WITH LABORATORY
EQUIPMENTS
AIM:
To familiarize with laboratory equipments: CRO, Multimeter and Function
Generator.
Cathode Ray Oscilloscope:
CRO is one of the most important instruments used in electronics lab. The
CRO is usually used to plot a changing voltage as a function of time, with the
instantaneous voltage read along the vertical or y- axis while time is measured
along the horizontal or x- axis. In digital applications, pulse waveforms can be
displayed and parameters such as amplitude, period, frequency, rise and fall times,
and duty cycle can be measured. Also two waveforms can be displayed
simultaneously so that their time relationship can be determined. The function of
the various controls of the CRO as follows:FRONT PANEL OF CRO
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VISAT, Elanji
Analog Circuits Lab
(1)
Power ON / OFF
:
Push buttons switch for supplying power to
instrument
(2)
X1 / X10
:
Switch when pushed inwards gives 5 times
magnification of the X signal
Switch when pressed cuts off the time base
& allows access the ext. horizontal signal
to be fed through CH II (used for X – Y
display).
Switch when out selects & triggers CH – I
and when pressed, selects & triggers II CH
II
(3)
XY
:
(4)
CH – I / CH – II /
TRIG II TRIG
:
(5)
MONO / DUAL
:
Switch selects the dual operation.
(6)
ALT / CHOP / ADD
:
Switch selects alternate or chopped in
DUAL mode. If mono is selected then this
switch enables. Addition or subtraction of
channel i.e.CH I ± CH II
(7)
TIME / DIV
:
Switch selects time base speeds
(8)
AT / NORM
:
Switch selects Auto / Normal position.
Auto is used to get trace when no signal is
fed at the input. In NORM the trigger
level can be varied from the positive peak
to negative peak with LEVEL control.
(9)
LEVEL
:
Controls the trigger level from peak to
peak amplitude of signal.
(10)
TRIG. INP
:
Socket provided to feed external trigger
signal in EXT. mode
(11)
NOR / ALT
:
Switch selects NOR (X1) or ALT (X1 &
X5 simultaneously) operation.
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Analog Circuits Lab
(12)
HOLD OFF
:
This provides the hold off to high
frequency and complex signal triggering
(13)
X - POS
:
Controls horizontal position of the trace.
Switch when pressed triggers high
frequency signal applied to CH I / CH II
input.
Controls the time speed in between two
steps of TIME / DIV switch.
For
calibration put this fully anticlockwise.
(At
CAL when
pos.) pressed allows external
Switch
triggering signal to be fed from the socket
marked TRIG. INP
(14)
HF
:
(15)
VARIABLE
:
(16)
EXT.
:
(17)
ALT Trig.
:
Selects alternate trigger mode from CH I &
CH II
(18)
+/-
:
Switch selects the slope of triggering,
whether positive going or negative going.
(19)
INV CH.II
:
Switch when pressed inverts the CH II.
(20)
INTENS
:
Controls the brightness of the trace.
(21)
TR
:
Controls the alignment of the trace with
graticule. (Screw driver adjustment)
(22)
FOCUS
:
Controls the sharpness of the trace.
(23)
ILLUM.
:
For switching
illumination
ON
/
OFF
graticule
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Analog Circuits Lab
(24)
CALOUT
:
(25)
CT - IN
:
Socket provided for square wave output
200mV; used for probe compensation and
checking vertical sensitivity.
To test any components in the component
tester mode, put one test probe in this
socket and connect the other test probe in
ground socket.
(26)
1mV
:
Switch when pressed magnifies the input
signal in Y direction. On 5mV position,
this improves the sensitivity to 1Mv
(27)
COMP. TESTER
:
Switch when pressed starts component
tester operation.
(28)
TRACE SEP.
:
Separates traces X1 & X5 in ALT
operation.
(29)
VOLTS / DIV
:
Switches select the sensitivity of each
channel.
(30)
Y POS I & II
:
Controls provided for vertical deflection of
trace for each channel.
:
Input coupling switch for each channel. In
AC the signal is coupled through 0.1 MFD
capacitor
:
BNC connectors serve as input connection
for CH I & CH II. Channel II input
connector also serves as horizontal external
signal.
:
350mA fuses is provided at the back panel.
Spare fuses are provided inside the
instrument.
(31)
(32)
DC / AC / GD
CH.I (Y) & CH.II(X)
BACK PANEL CONTROLS
1.
FUSE
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Analog Circuits Lab
2.
Z mod
3.
:
:
Banana socket provided for modulating
signal input i.e. Z – modulation.
Banana socket provided for saw tooth
output of 5Vpp.
APPLICATIONS OF CRO
1. To Measure The Amplitude Of A Signal
A DC voltage is measured by applying by applying to any one channel. The
amount of displacement of the spot on the screen (number of divisions) multiplied by
the deflection sensitivity (VOLTS/DIV)
An ac voltage can be measure by applying to any one channel. A trace is
obtained. Measure the width of the trace and multiply it with the deflection
sensitivity (VOLTS/DIV) gives the peak to peak value of the applied ac voltage. Half
of this voltage gives the peak of maximum value of ac. If the ac voltage is sinusoidal,
dividing the peak value by √2 gives the RMS value of the applied signal.
To Measure the frequency of the Signal
To determine the frequency of a signal using the oscilloscope, measure the time
period of the waveform. So, measure the number of horizontal divisions in the
oscilloscope screen. Then multiply the number of division with TIME/DIV to get the
time period. To determine the frequency, take the reciprocal of the time period.
Measurement of phase difference
When two sinusoidal waves are applied simultaneously to both pairs of
deflection plates, a Lissagious pattern is produced on the screen. The type of pattern
observed depends up on the ratio of the frequency of the two sine waves.
A CRO can be used to determine the phase difference between two sine
waves of the same frequency. The two voltages are applied to the two sets of
deflection plates simultaneously. The resultant pattern on the screen is an ellipse as
shown in figure. Now the phase difference between the two signals is given by
Sin θ = X1/ X2 = Y1/ Y2 ,where Y1 is the y- axis intercept, Y2 is the maximum
vertical deflection, X1 is the x- axis intercept and X2 is the maximum horizontal
deflection.
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Analog Circuits Lab
MULTIMETERS
Multimeter is an essential equipment to repair or trouble shoot on
electronic circuits. Multimeter, as its name indicates is used to measure various
electrical quantities such as voltage, current and resistance. Multi meter works in
different modes namely ammeter, volt meter and ohmmeter. The mode can be
selected using a selector switch provided in multimeter .Both AC and DC current
and voltages can be measured using the multimeter. These are available in two
types, called analog and Digital.
A digital multimeter displays the measured voltage, current or resistance as
discrete numerals instead of a needle deflection on a continuous scale as in an
analog multimeter. Numerical read out is advantages as it eliminate inaccuracies
due to parallax, human errors. Other advantage includes better resolution and
higher accuracy.
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Analog Circuits Lab
MEASUREMENT USING DIGITAL MULTIMETER
(a)
DC and AC Voltage measurement using DMM.
1.) Insert the positive and negative test leads in proper place
2.) Set the range selector switches to DCV/ACV range and connect the test
lead across the voltage under measurement is unknown. Set the range
selector switch to the highest range and work down to lower ranges.
(b). DC and AC Current measurement using DMM
1.) Connect the positive test terminal to the COM terminals and red lead to
the terminals marked for the measurement of current up to 2A. For the
measurement of current in the range from 2A to 20A, connect the red lead to
20A terminals.
(c) Resistance Measurement using DMM.
1.) Insert the positive end negative test leads in proper places. Set the range
selector switch in the ohm range and connect the test leads across the
resistance under measurement.
(d) Continuity Measurement
After setting up the electronic circuits, it is a good practice to verify the
shorts and open in the circuit. For this set the multimeter in the alarm range.
If there is continuity between lead tips it will make a beep sound.
(e) Transistor measurement.
To test the transistors connect the meter as below:
1.) Insert the transistor (NPN or PNP) in the respective sockets provided.
2.) The measured value will be displayed on the LCD display.
FUNCTION GENERATOR:
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Analog Circuits Lab
Many of the experiments need sinusoidal and square waves. Function
generator provides various signals with a provision to vary the frequency and
amplitude. In almost all of the function generators three types of waveforms
are available: sine, square and triangular. The frequency range of the function
generator is generally 0 – 2MHz. A knob named offset is provided to add
positive or negative DC voltage to the generated signal. If the operator does not
need any DC shift, by turning off this knob effect can be nullified and thus the
signal can be made to swing exactly with respect to zero reference.
Front Panel Controls:
1
Power
:
Push button switches to supply power to the
instrument
2
Digital Display (Seven
segment LED)
:
Four digit display for frequency of the
output.
3
Frequency
switches
:
Select frequency steps from 2Hz to 2MHz.
Selected frequency is indicated by glowing
LED.
selection
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Analog Circuits Lab
4
Function
switch
Selection
:
Selects desired function output shown by
respective glowing LED.
5
Modulation
(Position
push button switch)
:
Select the type of modulation or internal
sweep. Select type modulation is indicated
by respective glowing LED.
6
Output (BNC connector)
:
Terminal for taking output from function
generator
7
Sweep rate
:
Control provided to vary internal sweep.
8
Duty cycle
:
When pulse output function is selected this
controls the pulse duty cycle from 15% 85%.
9
Frequency Variable
:
In conjunction with frequency range switch
(3) this varies the output frequency.
10. Amplitude Variable
:
In conjunction with attenuators (10) this
varies the level of the output.
:
This control provides DC offset approx.
±5V DC is super imposed on the output.
Keep the control off if DC offset is not
required.
:
Combination 20dB and 40dB attenuation is
provided; when both pressed it becomes
60dB.
:
BNC terminal provided to feed the
modulating signal. The max of 2Vpp is
limit.
11
12
13
DC offset
Attenuator
Mod in
RESULT:
Familiarized with laboratory equipments like CRO, Multimeter and
Function Generator and studied how to measure frequency and amplitude of a
signal using CRO.
***********
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Department of Electronics & Communication
VISAT, Elanji
Analog Circuits Lab
Exp No: 2
Date :
Rectifiers and filters with and without shunt capacitors
AIM:To find the efficiency of half wave and full wave rectifiers and the ripple factor with and
without capacitor filter.
COMPONENTS AND EQUIPMENTS REQUIRED:Diodes, resistor, step down transformer, voltmeter, ammeter, breadboard and CRO.
THEORY:Rectifier changes ac to dc and it is an essential part of power supply. The
unique property of a diode permitting the current to flow only in one
direction, is utilized in rectifiers.
HALF WAVE RECTIFIER: Mains power supply is applied at the primary
of the step down transformer. The entire positive half cycles of the stepped
down ac supply pass through the diode and the entire negative half cycles
get eliminated.
For a half wave rectifier, Vrms = Vm/2, VDC = Vm/π, where Vrms=rms value
of input, VDC = Average value of input and Vm=peak value of output.
Ripple factor r = ((Vrms2/VDC2) - 1)1/2. It can be seen that r = 1.21 by
substituting the values.
FULL WAVE RECTIFIER: During positive half cycle of secondary
voltage, the diode D1 is forward biased and D2 is reverse biased. Then the
current flows through the diode D1, load resistor RL and upper half of
transistor winding. During negative half cycles, diode D2 becomes forward
biased and D1 becomes reverse biased. The current then flows through the
diode D2, load resistor RL and the lower half of transformer winding. Load
current in both the cases is in same direction.
For a full wave rectifier, Vrms = Vm/√2, VDC = 2Vm/π, where Vrms=rms
value of input, VDC = Average value of input and Vm=peak value of output.
Ripple factor r = ((Vrms2/VDC2) - 1)1/2. It can be seen that r = 0.48 by
substituting the values.
BRIDGE RECTIFIER: During the positive half cycles of the secondary
voltage, diodes D2 and D4 are conducting and diodes D1 and D3 not
conducting. Therefore, current flows through the secondary winding, diode
D2, load resistor, and diode D4. During the negative half cycles of the
secondary voltage, diodes D1 and D3 are conducting and diodes D2 and D4
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Analog Circuits Lab
not conducting. Therefore, current flows through the secondary winding,
diode D1, load resistor, and diode D3. In both cases, the current passes
through the load resistor in the same direction. The ripple factor of the
bridge rectifier is same as that of full wave rectifier.
PROCEDURE:1. The connections are made as shown in the circuit diagram.
2. Switch ON the supply. Observe the transformer secondary voltage waveform
and output voltage waveform across the load resistor, simultaneously on the
CRO screen. Note down the peak values.
3. Calculate the ripple factor using the expression.
4. Repeat the above steps for full wave and bridge rectifiers.
CIRCUIT DIAGRAM:-
Fig: Circuit Diagram of half wave rectifier
Fig: Input & Output waveforms
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Analog Circuits Lab
Fig: Circuit diagram full wave rectifier
Fig: Output waveform for the circuit
Fig: Circuit diagram full wave rectifier with capacitor
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Analog Circuits Lab
Fig: Output waveform for the circuit
Fig: Circuit diagram for Bridge rectifier without capacitor
Fig: Output waveform for the circuit
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Analog Circuits Lab
Fig: Circuit diagram for Bridge rectifier without capacitor
Fig: Output waveform for the circuit
RESULT
Familiarized with half wave and full wave rectification with and
without shunt capacitance.
*******
Viva Questions
1. How does the performance of the capacitor input filter improve when RC time
constant is increased?
2. What are the merits and demerits of CLC filter?
3. Why the capacitor input filter is called so?
4. What is the peak value of the waveform that can be observed if the output of a 6V
transformer is fed to a CRO?
5. What are the PIVs of three different rectifiers?
6. What are the advantages of bridge rectifier over center tapped FWR?
7. What is the TUF for full wave rectifier and bridge rectifier?
14
Department of Electronics & Communication
VISAT, Elanji
Analog Circuits Lab
Exp No: 3
Date :
CLIPPING CIRCUITS
AIM:To study various clipping circuits and observe their output wave forms.
COMPONENTS & EQUIPMENTS REQUIRED:-
COMPONENTS
SPECIFICATIONS
Diode
1N 4007
Resistor
3.3K
Function generator
Bread board
CRO
QUANTITY
1
1
1
1
1
THEORY:Clipping refers to removing a portion of the input signal that lies above or
below a reference level. Clipping or limiting is a linear wave shaping process by
which we can extract desired part of the input signal as necessary. Limiting circuits
are utilized in radio receivers to avoid the noise pulses that rise above the average
signal amplitude.
Capability of the diodes to permit current flow only in one direction enables
them to be used as the clipping devices. Diode clipping circuits can be classified as
series and shunt clippers. If the diode is connected in series with the input, the
circuit is a series clipper. On the other hand, the circuits with diode connected in
parallel to the input are called shunt clippers. Considering the positive parallel
clipper circuit, the output is taken across the diode. During positive half cycle of
the input, the diode is forward biased and hence no output results. But during
negative half cycle, diode is reverse biased and therefore the signal is transferred to
output terminals. Thus the waveform obtaining from the circuit will have only
negative half cycle. Since the diode will be in off state until knee voltage is
reached, a slice of the positive signal up to 0.6V will also appear in the output.
In the case of negative parallel clipper circuit, during negative half cycle of
the input, the diode is forward biased and hence no output results. But during
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Analog Circuits Lab
positive half cycle, diode is reverse biased and therefore the signal is transferred to
output terminals. Thus the waveform obtaining from the circuit will have only
positive half cycle. Since the diode will be in off state until knee voltage is
reached, a slice of the negative signal up to 0.6V will also appear in the output.
By providing a DC bias, TURN-ON of the diode can be advanced or
delayed as needed. Combinational clipping circuit helps us to extract the signal
between any two desired voltage levels. One of the parallel paths is for positive
half cycle and other for negative part of the signal. A resistance is incorporated
in to all clipping circuits with the purpose of limiting the current flow through the
diode. Its value is given by the expression,
For 1N4001:
The series resistance R = √Rf × Rr, where Rf is the forward resistance of the diode
and Rr is the reverse resistance.
Typical values of IN4001 are Rf = 10Ω, Rr=100K
PROCEDURE:1.
2.
3.
4.
Setup the circuit as shown in figure.
Apply sinusoidal signal with 12V peak to peak from the function generator.
Observe the output in CRO and note down voltage levels.
Transfer characteristics of the circuit can be observed by feeding Vin to CH 1
and Vo to CH 11 of the CRO and activating X-Y mode.
5. Repeat the process for various clipping circuits.
CIRCUIT DIAGRAM:
OUTPUT
TRANSFER CHARA
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Analog Circuits Lab
RESULT:Studied the characteristics of different clipping circuits and observed
their output wave forms.
******
Viva Questions:
1. Define clipper, limiter and slicer.
2. What is the application of clippers?
3. What is the need of resistance in clipping circuits?
4. Why is the resistance mentioned above taken as (Rf*Rr)1/2 ?
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Department of Electronics & Communication
VISAT, Elanji
Analog Circuits Lab
Exp No: 4
Date :
CLAMPING CIRCUITS
AIM:To design and set up various clamping circuits using diode and study their
performance.
COMPONENTS AND EQUIPMENTS REQUIRED:COMPONENTS
SPECIFICATIONS
Diode
1N 4007
Resistor
3.3K
Capacitor
1µF / 25V
Function generator
Bread board
DC power supply
CRO
QUANTITY
1
1
1
1
1
1
PRINCIPLE:In some situations it is necessary to add or subtract a DC voltage to a given
waveform without changing the shape of waveform. Circuits used for this purpose
are called clamping circuits. A capacitor which is charged to a voltage and
subsequently prevented from discharging can serve as a suitable replacement for
battery. This principle is utilized in clampers. Clamping circuits are also called DC
restoring or inserting circuits.
1. Clamping negatively at 0.7v:During positive half cycle of input sine wave diode conducts and capacitor
charges to Vm with negative polarity at right side of the capacitor. During negative
half cycle, the capacitor cannot discharge as the diode will not conduct. Thus the
capacitor act as a source of Vm-0.7v connected in series with the input signal. Then
output voltage, VO= -Vm+ 0.7+ Vm Sin wt.
2. Clamping positively at 0.7v:During negative half cycle diode conducts and charges to Vm-0.7v with
positive polarity at the right side of the capacitor. During positive half cycle,
capacitor cannot discharge due to diode being non- conducting. Thus capacitor acts
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Analog Circuits Lab
as a DC source of Vm- 0.7v connected in series with input. Then output voltage,
VO= Vm +0.7v +Vm Sin wt.
3. Clamping positively at 2.3v:During the negative half cycle the capacitor charged through DC source and
the diode till (Vm+ 3 – 0.7v) with positive polarity at its right side. The charging of
capacitor is extended up to (Vm + 3 – 0.7v) due to the presence of DC source. Then
output VO = (Vm+ 3 - 0.7v) + Vm Sin wt.
4. Clamping negatively at 3.7v:During negative half cycle the capacitor charged through DC source and the
diode till (Vm - 3 - 0.7v) with negative polarity of the capacitor at its right side. The
charging is limited to (Vm- 3- 0.7v) due to the presence of Dc source. The output
voltage, VO = - (Vm-3-0.7v) +Vm Sin wt.
5. Clamping negatively at -2.3v:During positive half cycle the capacitor charged through DC source and the
diode till (Vm + 3 – 0.7v) with negative polarity of the capacitor at its right side.
The charging is extended to (Vm+ 3 – 0.7v) due to the presence of DC source. The
output voltage, VO= - (Vm + 3 – 0.7v) + (Vm Sin wt).
PROCEDURE:1.
2.
3.
Connections are made as shown in figure.
From the function generator give a sine wave with 20v peak to peak to the
input of the circuit. Using another probe connect this input to CH 11 of the
CRO.
Output of the circuit is connected to the other channel of the CRO and
observed the input and output wave forms at the same time. Characteristic
curves can also be seen in the CRO.
CIRCUIT DIAGRAM:
OUTPUT
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Analog Circuits Lab
RESULT:_
Designed and set up various clamping circuits and their characteristics.
******
Viva Questions:
1. What are the other names of clamping circuits?
2. Give an application of clamping circuits?
20
Department of Electronics & Communication
VISAT, Elanji
Analog Circuits Lab
Exp No: 5
Date :
ZENER DIODE VOLTAGE REGULATOR
AIM:To setup and study a Zener diode voltage regulator circuit and plot its line
and load regulation characteristics.
COMPONENTS AND EQUIPMENTS REQUIRED:COMPONENTS
Zener diode
Voltmeters
Ammeters
Rheostat
Capacitor
DC power supply
Bread board
CRO
SPECIFICATIONS
SZ 6.8
(0- 15)V
(0- 100mA)
(0 - 50)mA
470Ω/1A
330µF
QUANTITY
1
2
1
1
2
1
1
1
1
THEORY:A PN junction diode specially designed with sharp breakdown voltage and
doped to operate in the breakdown region is called Zener diode. The characteristics
of Zener diode exhibit a unique capability to maintain a constant voltage drop after
the breakdown point in the reverse biased condition. i.e.; increase in the biasing
voltage does not affect the drop across Zener diode although the current can be
observed rising at very high rate. This feature enables the Zener diode used as a
voltage regulating device.
The source voltage is applied to the Zener diode through a series resistance
RS and the load resistor is connected across the diode. Current flowing through R S
is given by IS = IL +IZ , where IL is the load current, IZ is the Zener current
As the input voltage increases beyond VZ , current IS also increases. The
excess current will be directed through the diode as it permits lower resistance path
compared to load resistor RL. Thus the output current and hence the output voltage
remains constant. Similarly changes in the output voltage due to load variations are
also neglected by adjustments in the Zener current automatically.
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Thus VO remains constant in spite of the changes in the voltage or load
resistance.
If the Zener current falls below the minimum value to keep the diode in the
breakdown region, the regulation will cease and output will vary. Also higher
Zener current than the rated maximum will damage the device. Hence it is
important to design ‘RS’ such that sufficient and safe value of ‘IZ’ is obtained for
the given voltage limits.
DESIGN:Let Vi = 10V, IL = 35mA – 55mA, IZ = 5 – 20mA
V0 = 6.8V, Vi = V0 + VRS
VRS = Vi – V0 = 10 – 6.8 = 3.2V
RLmin = V0 / ILmax = 6.8 / 55 = 123Ω
RLmax = V0 / ILmin = 6.8 / 35 = 195Ω
Use 470ohm rheostat.
RSmax = VRS / Imin = 3.2 / 55 = 58Ω
RSmin = VRS / ILmax = 3.2 / 60 = 53Ω
RSmin < RS < RSmax
Select RS as 56Ω.
P = Im2RS = 0.062 * 56 = 0.2W
PROCEDURE:1. Line Regulation:1. Implement the voltage regulator circuit on the breadboard.
2.
For line regulation keep IZ at 5mA by adjusting rheostat (or keep
the rheostat at maximum resistance position and note the ammeter
reading).
3.
Vary input voltage from 7 to 15V and note the corresponding
output voltage.
4.
Plot the line regulation characteristics taking Vin along X- axis
and VO on Y- axis.
2. Load Regulation:1.
For load regulation, keep the input voltage at 12V.
2.
Vary the rheostat for varying values of IL and note the
corresponding output voltage.
3.
Plot the load regulation characteristics taking IL on X- axis and
VO on Y- axis.
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Analog Circuits Lab
4.
Calculate percentage of regulation by using the formulae.
Percentage load regulation= [(VNL-VFL )/VNL ]X 100%
CIRCUIT DIAGRAM:
TABULATION:
LINE REGULATION
IL = 5mA
VIN (Volts)
VOUT (Volts)
LOAD REGULATION
VIN =12V
IL (mA)
VOUT
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Model graph:
RESULT:Zener diode voltage regulator circuit has been studied and plotted its line
and load regulation characteristics.
% of line regulation =
% of load regulation =
******
Viva Questions:
1. State a demerit of zener regulator.
2. What is the difference between zener diode and ordinary diode?
3. What is line regulation?
4. What is load regulation?
24
Department of Electronics & Communication
VISAT, Elanji
Analog Circuits Lab
Exp No: 6
Date :
RC COUPLED AMPLIFIER
AIM
To design and set up RC coupled amplifier in common emitter configuration
and plot its frequency response.
COMPONENTS REQUIRED:-
COMPONENTS
Transistor
Resistor
Capacitor
SPECIFICATIONS
BC107
12KΩ
2.2KΩ
1.8KΩ
470Ω
10µF
100µF
Function generator
Bread board
CRO
QUANTITY
1
1
1
1
2
1
1
THEORY
Base current controls the collector current of a common emitter amplifier. A
small increase in base current results in a relatively large increase in collector
current. Similarly, a small decrease in base current causes large decrease in
collector current. The emitter – base junction must be forward biased and the
collector – base junction must reverse biased for the proper functioning of an
amplifier. Common emitter amplifier accomplishes current and voltage
amplification. In the circuit diagram, an NPN transistor is connected in a common
emitter AC amplifier. R1 and R2 are used for forward biasing the base – emitter
circuit. VCC is the DC supply which supplies collector current to the transistor. It
also functions as a source voltage to the voltage divider R1 and R2. The input signal
VM is coupled through CC1 to the base and output voltage is coupled from collector
through the capacitor CC2.
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Analog Circuits Lab
PROCEDURE
1. The circuit was set up as per the circuit diagram without connecting the
capacitor.
2. The DC conditions are checked. When the DC conditions are satisfied, the
capacitors are connected and the output supply is given.
3. Keeping the amplitude constant, the input frequency is varied from 50Hz to
1MHz and the corresponding output voltage was noted.
4. Then the frequency response curve is plotted.
DESIGN
Let VCC = 9v, IC = 2mA, hfe = 150, Select BC107
VCC = VCE + VRE + VRC
VCE = 50% VCC = 4.5v
VRE = 10% VCC = 0.9v
VRC = 40% VCC = 3.6v
VRE = ICRE
0.9 = 2mA * RE
RE =
0.9
2 103
= 0.45 10 3 = 450Ω
VRC = ICRC
RE =
3.6
2 103
= 1.8 10 3 = 1800Ω = 1.8KΩ
VR2 = VBE + VRE = 0.6+0.9 = 1.5v
VCC = VR2 + VR1
VR1 = VCC - VR2 = 9-1.5 = 7.5v
RB = R1 || R2
 R 
1   1  B 
 RE 
S=
R
1   B
RE
R 

1   1  B 
 450 
5=
R
1   B
450
RB = 1.9KΩ
26
Department of Electronics & Communication
VISAT, Elanji
Analog Circuits Lab
R1 =
9 1.8 103
1.5
= 12KΩ
R1 = 2.2KΩ
Take XCE = RE
10
1
= RE
C
10
1
= RE
2 fCE
10
XCC2 < RC
XCC2 =
RC
10
1
R
= C
2 fCC 2
10
R
XCC1 = in
10
Rin = RB || βRE
CE = 7.077 105
XCC2 =
RC
10
1
R
= C
2 fCC 2
10
CC2 = 3.18 10 5
CIRCUIT DIAGRAM:-
27
Department of Electronics & Communication
VISAT, Elanji
Analog Circuits Lab
FREQUENCY RESPONSE
Band width = f2 – f1
RESULT
The circuit of RC coupled amplifier has been set up and frequency response
curve is plotted.
Mid band gain =
dB
Band width =
kHz
28
Department of Electronics & Communication
VISAT, Elanji
Analog Circuits Lab
*****
Viva Questions
1.
2.
3.
4.
5.
6.
7.
What is meant by Q point?
What happens to bandwidth if Cc is reduced?
What are the functions of RE?
Why the gain of amplifier decreases if CE is removed?
Why is the efficiency of Class A amplifier very low?
What are self bias and fixed bias?
Give some examples of RC coupled amplifier?
29
Department of Electronics & Communication
VISAT, Elanji