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AB18
RC-COUPLED AMPLIFIER
Analog Lab
Experiment Board
Ver. 1.0
QUALITY POLICY
To be a Global Provider of Innovative and Affordable
Electronic Equipments for Technology Training by
enhancing Customer Satisfaction based on
Research, Modern manufacturing techniques and
continuous improvement in Quality of the products
and Services with active participation of employees.
An ISO 9001: 2000 company
94-101, Electronic Complex, Pardesipura INDORE-452010, India.
Tel.: 91-731-2570301 Fax: 91-731-2555643
AB18
Email: [email protected] Web: www.scientech.bz
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RC-COUPLED AMPLIFIER
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TABLE OF CONTENTS
1.
Introduction
4
2.
Theory
6
3.
Experiments
a.
Experiment 1
10
To study the operation of RC – coupled Amplifier
b.
Experiment 2
12
To study the frequency response of RC – coupled
Amplifier.
Datasheet
14
4.
Warranty
16
5.
List of service Centers
17
6.
List of Accessories with AB18
18
7.
Notes
19
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INTRODUCTION
AB18 is a compact, ready to use RC – COUPLED AMPLIFIER
experiment board. This board is useful for students to understand the
working and operation of coupling used to cascade various amplifier stages.
It can be used as stand alone unit with external DC power supply or can be
used with SCIENTECH ANALOG LAB ST-2612 which has built in DC
power supply, AC power supply, function generator, modulation generator,
continuity tester, toggle switches, and potentiometer.
List of Boards :
Model
AB01
AB02
AB03
AB04
AB05
AB06
AB07
AB08
AB09
AB10
AB15
AB16
AB17
AB19
AB21
AB22
AB23
AB25
AB28
AB29
AB30
AB31
AB32
AB33
AB40
AB41
Name
Diode characteristics (Si, Zener, LED)
Transistor characteristics (CB NPN)
Transistor characteristics (CB PNP)
Transistor characteristics (CE NPN)
Transistor characteristics (CE PNP)
Transistor characteristics (CC NPN)
Transistor characteristics (CC PNP)
FET characteristics
Rectifier Circuits
Wheatstone Bridge
Common Emitter Amplifier
Common Collector Amplifier
Common Base Amplifier
Cascode Amplifier
Class A Amplifier
Class B Amplifier (push pull emitter follower)
Class C Tuned Amplifier
Phase Locked Loop (FM Demodulator &
Frequency Multiplier)
Multivibrators (Astable / Monostable)
F-V and V-F Converter
V-I and I-V Converter
Zener Voltage Regulator
Transistor Series Voltage Regulator
Transistor Shunt Voltage Regulator
Op-amp Characteristics
Differential Amplifier (Transistorized)
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AB42
AB43
AB44
AB45
AB51
AB52
AB53
AB56
AB65
AB66
AB67
AB81
AB82
AB83
AB84
AB90
AB91
AB92
AB93
Operational Amplifier (Inverting / Noninverting / Differentiator)
Operational Amplifier (Adder/Scalar)
Operational Amplifier (Integrator/
Differentiator)
Schmitt Trigger and Comparator
Active filters (Low Pass and High Pass)
Active Band Pass Filter
Notch Filter
Fiber Optic Analog Link
Phase Shift Oscillator
Wien Bridge Oscillators
Colpitt Oscillator
Kirchoff’s Laws (Kirchoff’s Current Law &
Kirchoff’s Voltage Law)
Thevenin’s and Maximum power Transfer
Theorem
Reciprocity and Superposition Theorem
Tellegen’s Theorem
Two port network parameter
Optical Transducer (Photovoltaic cell)
Optical Transducer (Photoconductive cell/LDR)
Optical Transducer (PhotoTransistor)
…. and many more
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THEORY
Single amplifier circuits, such as a common emitter, common base and
common collector amplifiers are seldom found alone, as a single stage
amplifier, in any system. Generally, at least two or more than two stages
are connected in cascade combination. If the output of one amplifier is
connected (coupled) to the input of another amplifier the stages are said to
be connected in "cascade". The benefit of cascaded amplifiers is to develop
an output voltage larger than either stage alone can develop. In fact, the
overall gain of the cascaded amplifiers (called system gain) is the product
of each individual stage gain, or
AV
=
AVl
X
AV2
X
AVn ………….(1)
Total Voltage = gain of X gain of
X gain of any
Gain
first stage second stage
number of stages
Fig. 1
Because of this the gain of a single stage is not as important as the system
gain. Designers usually set individual stage gains relatively low to reduce
signal distortion. One of the very important requirements to cascade one
stage of amplifier to another is the impedance matching. When the output
impedance of pervious stage matches with the input impedance of its next
stage, maximum power is transferred. One of the coupling methods to
couple the two stages is RC-coupling. RC Coupling has the advantages of
wide frequency response and relatively small cost and size.
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RC Coupled Amplifier Stages
Fig. 2
An RC-Coupled network is shown in fig.2. The network of R2 and Cl
enclosed in the dashed lines is the coupling network. C1 is the coupling
capacitor which connects the output of Ql to the input of Q2. R2 will
develop the signal to be applied to the base of Q2. Cl acts as a limiting
Figure 3a
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Fig. 3
Figure 3b
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factor at low frequencies because its reactance increases with a decrease in
frequency and some point will be reached when a voltage drop will appear
across it. This will reduce the size of the signal being applied to Q2. At
medium frequencies the reactance of Cl is so small that it can be considered
a short to the signal. C1 will also isolate any DC voltage developed at the
collector of Q1 from the DC bias developed at the base of Q2.
Consider fig.3a, assume that Ql and Q2 are in a static slate, (no signal
applied). Let current flow through Ql develops 6VDC at the collector (Vc)
and current flow through the base biasing network of Q2 (R21 and R22)
develops 2VDC at the base of Q2 (Vb). Cc charges through R22 to the
difference in the potentials on either side of it and will assume a charge of
4VDC (6V-2V = 4V).
When a signal is applied to the base of Ql, the current changes through the
collector resistor (Rcl) will cause the Ql collector voltage to vary. In this
instance assume the collector rises to 7V. See figure 3b. As collector
voltage rises, the tendency of Cc is to charge to the higher potential.
However, a capacitor cannot change its charge instantly. As Cc starts to
change its charge, charge current will be felt through R22. Cc will now start
to change to lV. As Cc increases its charge, additional current will be drawn
through R22 causing R22 to increase its voltage drop. The voltage at Q2's
base, which is the voltage drop across R22, will now rise from 2V to 3V. As
the collector voltage at Ql starts to decrease. Cc will attempt to discharge.
Electrons being forced off the right plate of Cc, as it attempts to discharge,
will now flow through R21 increasing its voltage drop which results in a
decrease in the voltage drop across R22.
As Ql's collector voltage decrease further it will result in Cc decreasing its
charge further. As Ql collector voltage drops to 5V, Cc will continue to
attempt to discharge. As Cc continues to discharge, the voltage drop of R22
decreases to 1V. As Q1 collector voltage starts to go positive, Cc will start
to increase its charge. This causes the current through R22 to increase
which results in the voltage drop across R22 increasing. When the collector
voltage of Q1 returns to its original 6V the voltage at Q2's base will have
returned to 2V.
Notice that the signal developed at the collector of Ql has caused Cc to vary
its charge resulting in varying current level through R22 and R21. The
signal developed by these currents resulted in a signal being developed at
the base of Q2 which is identical to Ql's collector signal. Although the
signals on both sides of the capacitor are identical, the base signal of Q2 did
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not pass through Cc, it just appears to. Normally we would say "the signal
developed by Ql will be coupled by Cc to Q2's base".
Bandwidth of an RC - Coupled Amplifier :
Bandwidth is a term used to describe the band of frequencies a particular
amplifier will effectively amplify.
Fig. 4
The f1 and f2 points are also known as half power points. The half power
points are the points at which the signal amplitude has dropped to .707
percent of the maximum signal amplitude. Any frequency below the f1 or
above the f2 point is not considered a usable output from the amplifier. The
bandwidth of the amplifier is the difference between the f1 and f2 points. It
is generally accepted that in an RC -Coupled amplifier the fl point is
established by the coupling capacitor and by-pass capacitor and the f2 point
is set by the "shunt" or "stray wire" capacitance.
The bandwidth of RC-Coupled Amplifier is given by,
Bandwidth (B) = f2 – f1
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…………….(2)
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EXPERIMENT 1
Object :
To study the operation of RC – Coupled amplifier.
Apparatus required :
1.
2.
Analog board AB18.
3.
Function Generator.
4.
Oscilloscope.
5.
2mm patch chords.
DC power supply +12V from external source or ST-2612 Analog
Lab.
Circuit diagram :
Circuit used to study the operation of RC-Coupled amplifier is shown
below :
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Fig. 5
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Procedure :
•
Connect +12V variable dc power supplies at their indicated
position from external source or ST2612 Analog Lab.
1.
Connect 2Vp-p, 1 KHz Sine wave signal at the input (between points
Vin and g1) of amplifier named Stage1 of AB18 board and observe
the same on oscilloscope CH I.
2.
Connect point b and c using a 2mm patch cord (this will connect a
load RL at the output of Stage1.
3.
Observe the output waveform of Stage 1 between points a and g2.on
oscilloscope CH II.
4.
5.
Calculate the Voltage Gain (AV1).
6.
Observe the output waveform of Stage 2 between points Vout and g4
on oscilloscope CH II.
7.
8.
9.
Calculate the Voltage Gain (AV2).
10.
Connect 2Vp-p, 1 KHz Sine wave signal at the input (between points
Vin and g1) of amplifier named Stage1 of AB18 board and observe
the same on oscilloscope CH I.
11.
Observe the output waveform at Stage 2 between points Vout and g4
on oscilloscope CH II.
Apply the same signal (i.e. 2Vp-p, 1KHz Sine wave signal) to the
input of Stage2 (between points d and g3) of AB18 board and
observe the same on oscilloscope CH I.
Calculate Total Voltage Gain (Av) using Eq. (1).
Remove the pervious connections and connect point b with point d
of AB18 board. This will cascade the two stages through R C
coupling. Where Cc is the coupling capacitor and the combination of
R21 and R22 will act as coupling resistance.
12.
Calculate the Voltage Gain (AV’).
13.
Compare the two results obtained from step no.8 and 12.
Result :
Voltage Gain of Stage 1 [AV1 = Vout1/ Vin1] = ……………………..
Voltage Gain of Stage 2 [ AV2 = Vout2/Vin2 ] = ……………………
Av (from eq.1) =……………………..
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Av’ = ………………….
EXPERIMENT 2
Object :
To study the Frequency Response of RC – Coupled amplifier.
Apparatus required :
1.
2.
Analog board AB18.
3.
Function Generator.
4.
Oscilloscope.
5.
2mm patch chords.
DC power supply +12V from external source or ST2612 Analog
Lab.
Circuit diagram :
Circuit used to study the Frequency Response of RC-Coupled amplifier is
shown below:
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Fig. 5
Procedure :
•
Connect +12V variable dc power supplies at their indicated
position from external source or ST-2612 Analog Lab.
1.
Connect point b with d of AB18 board. This will cascade the two
stages through RC coupling. Where Cc is the coupling capacitor and
the combination of R21 and R22 will act as coupling resistance.
2.
Connect 1Vp-p, 100Hz Sine wave signal at the input (between points
Vin and g1) of amplifier named Stage1 of AB18 board and observe
the same on oscilloscope CH I.
3.
Observe the output waveform at Stage 2 between points Vout and g4
on oscilloscope CH II.
4.
Increase the amplitude of input signal to the value before the output
sine wave just gets distorted.
5.
Increase the input frequency value and observe the output waveform
amplitude on oscilloscope.
6.
Measure the maximum amplitude of the output sine wave and the
frequency range for which the output wave amplitude is 3dB down
the maximum amplitude.(this will give two valves of frequency fL
and fH, the lower 3dB frequency and higher 3dB frequency
respectively) as shown in fig.5.
7.
Calculate Bandwidth of RC-Coupled amplifier using Eq.2
Result :
f1 (lower 3dB frequency) = ……………………….
f2 (higher 3dB frequency) = ……………………….
Bandwidth (f2 – f1) = …………………….
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DATASHEET
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Scientech Technologies Pvt. Ltd.
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WARRANTY
1) We guarantee the instrument against all manufacturing defects during
24 months from the date of sale by us or through our dealers.
2) The guarantee covers manufacturing defects in respect of indigenous
components and material limited to the warranty extended to us by the
original manufacturer, and defect will be rectified as far as lies within
our control.
3) The guarantee will become INVALID.
a) If the instrument is not operated as per instruction given in the
instruction manual.
b) If the agreed payment terms and other conditions of sale are not
followed.
c) If the customer resells the instrument to another party.
d) Provided no attempt have been made to service and modify the
instrument.
4) The non-working of the instrument is to be communicated to us
immediately giving full details of the complaints and defects noticed
specifically mentioning the type and sr. no. of the instrument, date of
purchase etc.
5) The repair work will be carried out, provided the instrument is
dispatched securely packed and insured with the railways. To and fro
charges will be to the account of the customer.
DESPATCH PROCEDURE FOR SERVICE
Should it become necessary to send back the instrument to factory please
observe the following procedure:
1) Before dispatching the instrument please write to us giving full details
of the fault noticed.
2) After receipt of your letter our repairs dept. will advise you whether it
is necessary to send the instrument back to us for repairs or the
adjustment is possible in your premises.
Dispatch the instrument (only on the receipt of our advice) securely packed
in original packing duly insured and freight paid along with accessories and
a copy of the details noticed to us at our factory address.
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LIST OF SERVICE CENTERS
1. Scientech Technologies Pvt. Ltd.
90, Electronic Complex
Pardesipura,
INDORE – 452010
2. Scientech Technologies Pvt. Ltd.
First Floor, 14, Uday Park,
NEW DELHI – 110049
3. Scientech Technologies Pvt. Ltd.
New no.2, Old no.10, 4th street
Venkateswara nagar, Adyar
CHENNAI – 600025
4. Scientech Technologies Pvt. Ltd.
202/19, 4th main street
Ganganagar,
BANGALORE- 560032
5. Scientech Technologies Pvt. Ltd.
8,1st floor, 123-Hariram Mansion,
Dada Saheb Phalke road,
Dadar (East), MUMBAI –400014
6. Scientech Technologies Pvt. Ltd.
988, Sadashiv Peth,
Gyan Prabodhini Lane,
PUNE – 411030
7. Scientech Technologies Pvt. Ltd
SPS Apartment, 1st Floor
2, Ahmed Mamoji Street,
Behind Jaiswal Hospital,
Liluah, HOWRAH-711204 W.B.
8. Scientech Technologies Pvt. Ltd
Flat No. 205, 2nd Floor,
Lakshminarayana Apartments
‘C’ wing, Street No. 17,
Himaytnagar,
HYDERABAD- 500029
Scientech Technologies Pvt. Ltd.
Ph: (0731) 5202959
Email: [email protected]
Ph.: (011) 26513912, 26864943
Fax: (011) 26864943.
Email: [email protected]
Ph.: (044) 42187548, 42187549
Fax: (044) 42187549
Email: [email protected]
Ph.: (080) 51285011
Fax: (080) 51285022
Email: [email protected]
Ph.: (022) 56299457
Fax: (022) 24168767
Email: [email protected]
Ph.: (020) 24461673
Fax: (020) 24482403
Email: [email protected]
Ph.: +913355266800
Email: [email protected]
Ph.: (040) 55465643
Email: [email protected]
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LIST OF ACCESSORIES
1.
2mm patch cord (red)..............................................................1 No.
2.
2mm patch cord (blue)...........................................................4 Nos.
3.
2mm patch cord (black).........................................................4 Nos.
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NOTES
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NOTES
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