Aica 2 Mark Imp
Aica 2 Mark Imp
Aica 2 Mark Imp
UNIT-I
IC FABRICATION
PART-A
1. Mention the advantages of integrated circuits over discrete circuits. (AU ND 2016)
Advantages of Integrated Circuits over Discrete Circuits are,
i. Miniaturization and hence increased equipment density.
ii. Cost reduction due to batch processing.
iii. Increased system reliability due to the elimination of soldered joints.
iv. Improved functional performance.
v. Matched devices.
vi. Increased operating speed
2. What are the limitations of integrated circuits? (AU ND 2016)
The limitations of integrated circuits are
i. Faulty IC can’t be repaired; they have to be replaced by a new one.
ww ii. Some components like transformers and inductors cannot be integrated into an IC.
iii. High grade P-N-P assembly is not possible.
wiv. The IC will not work properly if wrongly handled or exposed to excessive heat.
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v. It is difficult to achieve low temperature coefficient.
vi. It is difficult to fabricate an IC with low noise.
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vii. It is not possible to fabricate capacitors that exceed a value of 30pF. Thus, high value
capacitors are to be connected externally to the IC.
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viii. There is a large value of saturation resistance of transistors.
3. What are the major categories of integrated circuits? (AU ND 2015)
Integrated Circuits can be classified based on
(i) Based on Mode of operation nee
(a) Digital I.C.
(b) Analog I.C. (Linear IC) rin
(ii) Based on fabrication
(a) Monolithic I.C. g.n
(b) Hybrid I.C.
(iii) Based on Integration level
(a) SSI -Small Scale I.C.
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(b) MSI-Medium Scale I.C.
(c) LSI - Large Scale I.C.
(d) VLSI - Very Large Scale I.C.
4. Explain why buried layer is needed. (AU ND 2014)
The buried layer is used in integrated transistor to decrease the collector series resistance.
it provides the low resistivity current path. The buried n+ layer shunts the n- epitaxial
collector layer effectively, decreasing the resistance.
5. What is Ion Implantation? Why it is preferred over diffusion process?
(AU ND 2014)
The conductivity of the semiconductor increases when small impurity is added to it. The
process of adding impurity is called doping while the impurity to de added is called dopant.
So ion implantation is a process of adding dopant to the silicon substrate. The ion
implantation process is controllable, reproducible and also there are no unwanted side
effects.
Downloaded From : www.EasyEngineering.net
Downloaded From : www.EasyEngineering.net EE 8451 Linear Integrated Circuits and Applications
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to this a heavily doped buried layer is formed. The buried layer is also called diffusion layer.
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10. What are the advantages of polysilicon gate MOSFET over aluminium gate?
14. Give the difference between monolithic and hybrid ICs. (AU ND 2010)
Monolithic IC Hybrid IC
1. In Monolithic circuits, all circuit 1.Hybrid Integrated circuits separated
components both active and passive component parts are attached to a
elements and their interconnections ceramic substrate and interconnected by
are manufactured into or on top of a means of either metallization pattern or
single chip of silicon. wire boards.
2. It is used for more applications in 2. It is used for adopt less applications
Linear and digital IC
3. Cost wise is less. 3. Cost wise is slightly higher compared to
monolithic ICs.
4. They are preferred only in low power 4.They are preferred for high power
applications. applications.
15. What is lithography? (AU ND 2010)
Lithography is a process by which the pattern appearing on the mask is transferred to the
ww wafer. It involves two steps: the first step requires applying a few drops of photo resist to
the surface of the wafer & the second step is spinning the surface to get an even coating of
the photo resist across the surface of the wafer.
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16. What is photolithographic process?
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(AU ND 2010)
Photolithography is a process used in micro fabrication to selectively remove parts o f a
th in f il m o r th e bu l k o f a substrate. It uses light to transfer a geometric
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pattern from a photo mask to a light-sensitive chemical "photoresist", or simply
"resist," on the substrate. A series of chemical treatments then engraves the exposure
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pattern in to the material underneath the photo resist. In complex integrated circuits, for
example a modern CMOS, a wafer will go through the photolithographic cycle up to 50
times.
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17. Why aluminium is preferred in metallization process? (AU ND 2009)
Aluminium is preferred in metallization process because,
i. It is relatively a good conductor rin
ii. It is easy to deposit aluminium films using vacuum deposition.
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iii. Aluminium makes good mechanical bands with silicon.
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iv. Aluminium forms low resistance, non – rectifying contact with p – type silicon and t
the heavily doped n – type silicon.
18. Compare the performance of n-p-n and p-n-p transistors with respect to IC
fabrication. (AU ND 2009)
The electron mobility in silicon is about 2.5 times than the hole mobility so the basic
transit time will generally be shorter in npn transistors than in pnp transistors. This
will lead to a somewhat higher current gain and to improved high frequency
performance for the npn transistors.
As a result of the higher solubility of the donor dopants compared to boron a more
efficient emitter base structure can be obtained in the case of an npn transistor than
in the case of pnp transistor. Thus trading to a higher current gain .the structure of
most bipolar ICs is based on the use of npn transistors.
Mobility of electrons than holes , npn transistors are more frequently used than pnp
transistors.
Downloaded From : www.EasyEngineering.net
Downloaded From : www.EasyEngineering.net EE 8451 Linear Integrated Circuits and Applications
19. What is meant by dielectric isolation? Mention its advantages and limitations.
(AU MJ 2009)
Dielectric isolation is defined as the isolation technique in which the electrical
isolation to each component is provided by surrounding them with a solid dielectric.The
most commonly used dielectric are silicon, dioxide, ruby etc.
The main advantages of the techniques are that within same silicon substrate p-n-p
as well as n-p-n transistors can be fabricated.
The disadvantages is the increase in the cost. As the technique needs additional
steps in fabrication to deposit a dielectric layer, this technique is expensive.
Hence this technique is used for fabricating ICs for special military applications where
performance of the circuit is of prime importance than the cost factor.
20. Define the term epitaxial growth. (AU MJ 2008)
The word epitaxy is derived from Greek word epi meaning “upon” and the past tense
of the word tension meaning “arranged”. So, one could describe epitaxy as arranging atoms
in single crystal fashion upon a single crystal substrate; so that the resulting layer is an
extension of the substrate crystal structure.
ww Generally the doping types of the substrate and the epitaxial layer are opposite to
provide isolation .thus n- type epitaxial layer is grown on p-type substrate which has
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resistivity of the order 1-2Ω cm .the epitaxial layer is useful as other components are
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fabricated within this layer. This layer may act as an element of diode, diffused capacitor of
collector of transistor.
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21. Differentiate between thin film and thick film technology in IC fabrication.
(AU ND 2007)
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The differences of thin film and thick film technology in IC fabrication are
i. Thin film resistors have a lower tolerance than the thick film resistors.
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ii. The capacitance of thin film resistors is lower than that of the thick film
resistors.
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iii. The temperature coefficient of thin film resistors is much lower than that of the
thick film resistors.
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iv. The production of thin film resistors is expensive than the production cost of
the thick film resistors.
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v. The process of manufacturing the thin film resistor is different from the
manufacturing process of the thick film resistors.
22. How are capacitors fabricated in ICs? Draw the cross sectional view of MOS
capacitor? (AU ND 2006)
It consists a implanted or diffused heavily doped within substrate while a polysilicon or
metal plate on the top of a thin oxide layer .for MOS capacitors, generally gate oxide is used
with no extra processing step.
24. Name the parameters which govern the thickness of the film in the oxidationprocess.
(AU ND 2005)
The main important parameter which governs the thickness of the film in the oxidation
process is temperature. Because to grow the oxide layer high temperature is to be
maintained. The other important parameters governing oxide film thickness are time up to
which process is to be carried out and the moisture contents.
25. What are the advantages of using dry etching process? (AU ND 2005)
The major advantage of using the dry etching process over wet etching process is that it is
possible to achieve smaller openings of thickness≤1µm.
PART-B
1. (i) Describe about epitaxial growth process (6)(AU ND 2016)
(ii)Explain in detail about the photolithography process with neat diagram.
(7)(AU ND 2016)
2. Write a note on masking and etching process in IC fabrication. (13)(AU ND 2016)
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3. Discuss the different ways to fabricate diodes.
4. Explain how a monolithic capacitor can be fabricated.
(10)(AU ND 2015)
(6)(AU ND 2015)
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5. Describe, in detail, any two isolation technique used to provide isolation between various
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components in IC fabrication with illustrations (8+8)(AU ND 2014)
6. Explain, in step by step basis, the fabrication of planar P-N Junction diode with neat
illustrations.
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7. Explain CMOS fabrication with neat sketches.
(16)(AU MJ 2014)
(8)(AU MJ 2014)
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8. What is photolithography? What is the purpose of diffusion?
9. List the methods for fabricating integrated resistors and explain.
(6)(AU MJ2014)
(10)(AU MJ 2014)
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10. What is a schottky transistor? Draw the cross sectional view and explain its operation.
(6)(AU ND 2014)
11. Explain about the following :
(i) Epitaxial growth and diffusion . rin (16) (AU ND 2013)
13. Explain the basic processes used in the fabrication of monolithic IC.
14. Explain the fabrication of n-channel JFET with necessary diagrams.
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(16)(AU ND 2013)
(16)(AU MJ 2012)
(16)(AU ND 2012)
15. Explain in detail the fabrication process of passive component in Integrated Circuits.
(16)(AU ND 2012)
16. With necessary diagrams explain the fabrications of MOSFET. (16)(AU MJ 2012)
17. Briefly explain the various types of IC packages. Mention the criteria for selecting an IC
package. (8)(AU MJ 2010)
18. Write short notes on classification of Integrated circuits. (8)(AU MJ 2010)
19. With respect to the BJT based circuit given below, explain the various steps to implement
the circuit into a monolithic IC. (16)(AU MJ2010)
20. Explain the basic processes used in silicon planar technology with neat diagram.
(16)(AU ND 2010)
21. Briefly explain the process of ion implantation in IC fabrication. (8)(AU ND 2009)
22. Discuss briefly the various steps involved in the fabrication of IC. Draw the layout of a
circuit by considering an example. (10)(AU ND 2007)
UNIT II
CHARACTERISTICS OF OPAMP
PART-A
1. Mention the applications of op-amp integrator. (AU ND 2016)
The operational amplifier integrator is an electronic integration circuit. Based around
the operational amplifier (op-amp), it performs the mathematical operation
of integration with respect to time; that is, its output voltage is proportional to the input
voltage integrated over time.
Applications:
The integrator circuit is mostly used in analog computers, analog-to-digital converters and
wave-shaping circuits. A common wave-shaping use is as a charge amplifier and they are
usually constructed using an operational amplifier though they can use high gain discrete
transistor configurations.
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2. What is integrator? (AU ND 2016)
An integrator in measurement and control applications is an element whose output signal is
the time integral of its input signal. It accumulates the input quantity over a defined time to
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produce a representative output. Integration is an important part of many engineering and
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scientific applications.
3. Draw the frequency response characteristics of an AC Integrator and indicate the part
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where it behaves as a true integrator. (AU ND 2015)
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4. State the causes for slew rate in an operational amplifier? How it is indicated? et
(AU ND 2014)
There is a capacitor with-in or outside of an op-amp to prevent oscillation. It is this
capacitor which prevents the output voltage from responding immediately to a fast
changing input. The slew rate is defined as the maximum rate of change of output voltage
caused by a step input voltage. It is given by in capacitor.
5. What is the value of open loop gain and output impedance of an ideal op-amp?
(AU ND 2013)
The value of open loop gain and output impedance of an ideal op-amp is,
i. Open loop gain is infinite. (A=∞)
ii. Output impedance is low. (z0=0)
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10. What is thermal drift?
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(AU ND 2011)
The bias current, offset current & offset voltage change with temperature. A circuit carefully
nulled at 25oC may not remain so when the temperature rises to 35 oC. This is called thermal
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drift. Often, offset current drift is expressed in nA/ oC and offset voltage drift in mV/ oC.
11. Define Input offset voltage and input offset current in an op-amp. (AU ND 2011)
Input offset voltage:
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This is the voltage required to be amplified at the input for making output voltage to zero
volts.
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It is the voltage that must be applied between the input terminals of an op-amp to nullify
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the output. Since this voltage could be positive or negative its absolute value is listed on the
data sheet.
Input offset current:
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The algebraic difference between the current into the inverting and non-inverting terminals
Where
IB+ is the current into the non-inverting input terminals.
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is referred to as input offset current Iio. Mathematically it is represented as I io = |IB+ - IB- |
13. Draw the circuit diagram of an integrator and give its output equation. (AU MJ 2010)
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14. Design an amplifier with a gain of –10 and input resistance of 10 k . (AU MJ 2010)
Given the gain of the amplifier is negative, an inverting amplifier has to be made.
Input resistance R1=10kΩ,
ACL= (Vo/Vi) =-(Rf/R1)
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Rf = -ACL R1 = - (-10) x 10kΩ
Rf = 100kΩ
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15. List the four non ideal dc characteristics of OP-Amp.
rin (AU ND 2010)
The non ideal dc characteristics of OP-Amp are
i. Input impedance g.n
ii. Output impedance
iii. Frequency response
iv. Slew rate
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16. Define slew rate and state its significance. (AU ND 2010)
The slew rate is defined as the maximum rate of change of output voltage caused by a step
input voltage. An ideal slew rate is infinite which means that op-amp’s output voltage
should change instantaneously in response to input step voltage.
The circuit of successive approximation ADC consists of a successive approximation
register (SAR), to find the required value of each bit by trial & error. With the arrival of
START command, SAR sets the MSB bit to 1. The O/P is converted into an analog signal & it
is compared with I/P signal. This O/P is low or high. This process continues until all bits are
checked.
17. What is a precision diode? Draw the circuit diagram of a half wave precision rectifier
with waveform. (AU MJ 2009)
Precision diode or super diode is a combination of opamp and diode which is a superior
rectifier .A diode in the feedback loop of an op-amp behaves as a precision diode as its cut-in
voltage gets divide by the open-loop gain of op-amp. Precision diode may be used for half-
wave rectification, full wave rectification, peak value detector, clipper and clamper.
18. In what way, a precision rectifier using op-amp is superior to a conventional rectifier?
ww (AU ND 2009)
These rectifiers are used to rectify very small voltages or currents for which the diode never
gets forward biased in the conventional one. i.e. voltage or currents are always less than .7V
wwhich cannot be rectified by normal rectifiers.
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This rectifier doesn’t give any kind of drop in output since diodes are previously biased
using op-amp.
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19. List the basic blocks of an operational amplifier.
An Op-Amp can be conveniently divided in to four main blocks
(AU ND 2009)
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i. An Input Stage or Input Diff. Amp.
ii. The Gain Stage CE Amp.
iii. The Level Translator or level shifter.
iv. An output Stage or buffer. nee
20. Compare ideal and practical characteristics of an op-amp.
ideal characteristics: rin (AU ND 2008)
22. Draw the circuit diagram of differentiator using op-amp. (AU MJ 2006)
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PART-B
1. Discuss in detail about the DC and AC characteristics of op-amp. (13)(AU ND 2016)
2. Explain the differential amplifier using op-amp. (13)(AU ND 2016)
3. Design an adder –subtrator circuit for V0=2V1+5V2-10V3 . (6)(AU ND 2015)
4. Determine the output voltage Vo and the current Io in the circuit as shown below.
(10)(AU ND 2015)
5. Obtain the closed loop voltage gain Vo/Vi of the circuit shown below. (16)(AU MJ 2014)
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6. Discuss in detail the DC characteristics of an Op-Amp. (16)(AU MJ 2014)
differentiator
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7. Explain briefly about how an operational amplifier is used as summer, integrator and
(16)(AU ND 2014)
amplifiers. ngi
8. With a neat diagram explain the working shunt feedback amplifiers and series feedback
(12)(AU ND 2014)
13. With neat diagrams explain the types of feedback configurations available.
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(16)(AU MJ 2012)
(8)(AU ND 2010)
14. Briefly explain the frequency response of op-amp. Give the frequency compensation
techniques adopted in operational amplifiers. (16)(AU ND 2010)
15. Explain the functions of all the basic building blocks of an Op-Amp. (8)(AU ND 2010)
16. Write a technical note on frequency response characteristics of differential amplifier. State
the importance of frequency compensation. (10)(AU ND 2009)
17. Explain various dc and ac characteristics of an op-amp. Distinguish between ideal and
practical characteristics. (12)(AU ND 2009)
18. Determine the output voltage of the differential amplifier having input voltages
V1=1 mV and V2 =2 mV . the amplifier has a differential gain of 5000 and CMRR 1000.
(4)(AU ND 2009)
19. Define input bias current and sate its effect on op-amp performance .explain how input bias
current compensation is obtained. (8)(AU ND 2007)
20. Design a practical differentiator circuit that will differentiate an input signal with maximum
frequency of 150Hz. (8)(AU ND 2007)
21. Design a op-amp circuit to give an output. (8)(AU ND 2007)
V0= V1-2 V2+ 2V3 -3 V4.
22. What are the methods used to improve the slew rate? Briefly explain. (8)(AU ND 2007)
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UNIT III
APPLICATIONS OF OPAMP
PART-A
1. What is sample and hold circuit? Where it is used? (AU ND 2016)
A sample and hold circuit is one which samples an input signal and holds on to its last
sampled value until the input is sampled again. This circuit is mainly used in digital
interfacing, analog to digital systems, and pulse code modulation systems.
2. Draw the circuit of a positive clipper. (AU ND 2016)
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3. What is the purpose of S/H in data converters?
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(AU ND 2015)
A Sample and Hold circuit is one which samples an input signal and holds on to its last
sampled value until the input is sampled again. This circuit is mainly used in digital
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interfacing, analog to digital systems, and pulse code modulation systems.
4. What is an instrumentation amplifier? (AU ND 2014)
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Instrumentation amplifier is defined as the special amplifier which is used for such a low
level amplification with high CMRR, high input impedance to avoid loading, low power
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consumption and some other features is called an instrumentation amplifier. It is also
called data amplifier and is basically a difference amplifier.
7. How many resistors are required in a 12-bit weighted resistor DAC? (AU ND 2013)
For 12 bit DAC the resistor required are 2 R, 2 R, 2 R….2 R. The largest resistor is 2048
0 1 2 n
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variable never decreases as the value of the independent variable increases.
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9. What are the applications of peak detectors?
The applications of peak detectors are
(AU ND 2012)
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i. Directional couplers to measure forward and reflected power on a transmission line
(it is the original application of this circuit);
ii. Low power wattmeter’s
iii. RF mill voltmeters
iv. Field strength meters
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v. Radio receivers
10. Why active filters are preferred?
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The active filters are preferred because
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i.
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Gain & Frequency adjustment flexibility: Since op-amp provides some gain, input
signal is not attenuated. Active filters are easier to time or adjust.
ii. No Loading Problem: Because of high i/p impedance & low o/p impedance of Op-
amp, active filters does not cause loading of source or load.
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iii. Cost: Active filters are more economical, because of cheaper op-amps and absence
of inductors.
11. Draw the circuit of first order active filter. (AU ND 2011)
12. Draw the circuit diagram of sample and hold circuit. (AU ND 2011)
13. Draw the circuit diagram of an op-amp based positive clipper. (AU ND 2011)
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14. List different parameters of the D/A and A/D converter given by the manufacturers.
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The parameters of the D/A and A/D converters are
(AU ND 2010)
i. Resolution
ii. Accuracy syE
iii. Monotonicity
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iv. Conversion time and settling time
v. Stability
vi. Quantization error nee
15. Which is the fastest ADC and why?
rin (AU ND 2010)-2
The circuit of successive approximation ADC consists of a successive approximation
g.n
register (SAR), to find the required value of each bit by trial & error. With the arrival of
START command, SAR sets the MSB bit to 1. The O/P is converted into an analog signal & it
checked.
16. An 8 bit DAC has a resolution of 20mV/bit. what is the analog output voltage for the
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is compared with I/P signal. This O/P is low or high. This process continues until all bits are
digital input code 00010110(the MSB is the left most bit)? (AU MJ 2010)
The output voltage for input 00010110 is
=20(0X28+0X27+0X26+1X25+0X24+1X23+1X22+0X21)
=20X44
=880mV
17. Draw the circuit of I-V converter using op-amp. State the application.
(AU MJ 2012)-2
Application:
i. The photocell, photodiode and photovoltaic cell gives an output current that is
proportional to an incident radiant energy or light.
ii. The current through these devices can be converted into voltage by using an I to V
converter and thereby the amount of light or radiant energy incident on the photo
device can be measured.
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18. What are the basic requirements of a good instrumentation amplifier? (AU ND 2009)
The basic requirements of a good instrumentation amplifier are,
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ii. Easier gain adjustment.
iii. High Input impedance.
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iv. Low output impedance.
v. High CMRR.
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vi. Low power consumption.
vii. Low thermal and time drifts.
viii. High slew rate.
19. Define resolution and accuracy of a DAC. nee (AU ND 2009)-3
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Resolution is the number of different analog output values that can be provided by a DAC.
For an n-bit DAC
Resolution=2n
g.n
Resolution is also defined as the ratio o a change in output resulting from a change of 1 LSB
at the digital inputs. For an n-bit DAC it can be given as
Resolution (in volts) = VFS/2n-1
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Accuracy:
It is the maximum deviation between the actual converter output & the ideal converter
output.
Relative accuracy:
It is the maximum deviation after gain & offset errors have been removed. The accuracy of a
converter is also specified in form of LSB increments or % of full scale voltage.
20. What is a monostable multivibrator? (AU MJ 2009)
Monostable multivibrator is one which generates a single pulse of specified duration in
response to each external trigger signal. It has only one stable state. Application of a trigger
causes a change to the quasi-stable state. An external trigger signal generated due to
charging and discharging of the capacitor produces the transition to the original stable
state.
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24. List any four important applications of a comparator. (AU ND 2007)
The applications of a comparator is
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i. Zero crossing detector
ii. Window detector
iii. Time marker generator
iv. Phase detector ngi
25. What are the advantages of active filters?
The advantages of active filters are nee (AU MJ 2007)
PART-B
1. Write a note on logarithmic and antilog amplifier using op amp. (13)(AU ND2016)
2. Explain the working of SAR type and flash type A/D converter. (13)(AU ND 2016)
3. A dual slope ADC uses 16-bit counter and 4MHz clock rate . the maximum input voltage is
+10V .The maximum integrator output voltage should be -8V when the counter has cycled
through 2n counts .the capacitor used in the integrator is0.1 µF. Find the value of resistor R
of the integrator. (6)(AU ND 2015)
4. Derive the expression for the log and anti log amplifiers with necessary diagrams.
(10)(AU ND 2015)
5. In a triangular wave generator given R2=1.2kΩ, R3=6.8kΩ,R1=120 kΩ,C1= 0.01 µF. determine
the peak to peak o/p amplitude of triangular wave and frequency of the triangular wave.
(8)(AU MJ 2015)
6. Design a RC phase shift oscillator for a frequency of 1kHz . (8)(AU MJ 2015)
7. Explain the operation of dual slop ADC with neat illustration. Also prove that this ADC is
free from drifts . (10+6)(AU MJ 2014)
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8. With neat schematic representations explain the operation of the following circuits?
(i)Positive peak follower.
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(ii)Active positive clamper to clamp the input signal above ground state by 5V.
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9. (i) Explain the operation of peak detector and S/H circuit.
(16)(AU MJ 2014)
(16)(AU ND 2014)-2
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(ii)What is the use of an A/D convertor . Explain the dual slop type of A/D convertor.
10. (i) Differentiate a clipper and a clamper with neat sketches.
(ii)Explain the operation of a regenerative comparator.
(6)(AU ND 2014)
(10)(AU ND2014)
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(16)(AU MJ2013)
14. Explain the working principle of RC phase shift sine wave generator using op-amp and
derive the expression for ‘f’. (16)(AU ND 2012)
15. Explain with neat circuit diagram of any one sine wave oscillator using op-amp and derive
expression for frequency of oscillation and gain of op-amp. (16)(AU ND 2012)-2
16. Explain in detail the working of (i)Weighted resistor type DAC(ii) Dual slope type ADC.
(16)(AU MJ 2011)
17. Explain the first order low pass Butterworth filter with neat circuit diagram. Derive its
frequency response and plot the same. (16)(AU ND 2010)
18. Design a low pass filter with a cutoff frequency of 1kHz and with a pass band gain of 2.
(16)(AU ND 2010)
19. What is an instrumentation amplifier? Give the important features of an instrumentation
amplifier. Explain the working of three op-amp instrumentation amplifier. Give its
application. (16) (AU MJ 2010)
20. (i)Design a monostable multivibrator using op-amp and obtain expression for pulse
width T. (8)(AU ND 2009)
(ii)Explain the working of clamper and sample /hold circuit. (8)(AU ND2009)
21. (i)Design a second order active high pass filter for a cut off frequency of 5kHz.
(8)(AU MJ2008)
(ii)Explain the functions of flash type A/D converter. (8)(AU MJ 2008)
22. (i)Write short notes on voltage to time converters. (10)(AU ND 2007)
(ii) What are the different sources of error in D/A converters. (6)(AU ND 2007)
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UNIT IV
SPECIAL ICs
PART-A
1. Draw the pin diagram of IC 555 timer (AU ND 2016)
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2. Define PLL. (AU ND 2016)
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A phase-locked loop (PLL) is an electronic circuit with a voltage or voltage-driven oscillator
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that constantly adjusts to match the frequency of an input signal. PLLs are used to generate,
stabilize, modulate, demodulate, filter or recover a signal from a "noisy" communications
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channel where data has been interrupted
3. What are the advantages of variable transconductance technique?
The advantages of variable transconductance techniques are,
(AU ND 2015)
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Simple to integrate in to monolithic chip.
Provides very good accuracy.
Very cheap hence economical nee
Provides four quadrant operation
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It provides high speed of operation which is 2 to 3 times more than the logarithmic
method.
Reduced error at least by 10 times. g.n
The bandwidth of 10 MHz and higher are available.
4. Why invariably a suitable value of capacitor is connected to the pin 5 of 555 timer
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applications? (AU ND 2015)
A suitable value of capacitor is connected invariably to the pin 5 of 555 timer applications
so as to bypass the unwanted ripples and noise present in the dc supply voltage, thereby
the DC threshold limits can be accurately maintained. If pin 5 is not used it is usually
grounded through a 0.01µF capacitor.
5. Draw the block diagrammatic representation of a frequency multiplier using PLL.
(AU ND 2014)
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iii. Automatic gain control
iv. True RMS converter
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v. Analog filter (especially voltage-controlled filters)
vi. PAM-pulse amplitude modulation
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Settling time represents the time it takes for the output to settle within a specified band+-
(1/2) LSB of its final value. It depends upon the switching time of the logic circuitry due to
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internal parasitic capacitances and inductances. Settling time ranges from 100ns to 10μs
depending on word length and type of circuit used.
Conversion time
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Conversion time is the time taken for the D/A converter to produce the analog output for
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the given binary input signal. It depends on the response time of switches and the output of
the Amplifier. D/A converters speed can be defined by this parameter. It is also called as
setting time.
10. What is the function of a voltage regulator? (AU MJ 2013)
A regulator circuit is a circuit used after the filter, which not only makes the dc voltage
smooth and almost ripple free but also keeps the dc output voltage constant though input
dc voltage varies under certain condition. Thus input to a regulator is an unregulated dc
voltage while the output of a regulator is a regulated dc voltage, to which the load is
connected.
11. What are the essential parts of PLL? (AU MJ 2013)
The essential parts of PLL is,
i. Phase comparator
ii. Low pass filter.
iii. Error Amplifier
iv. Voltage controlled oscillator
12. In a astable multivibrator using 555 timer RA =6.8 kΩ, RB =3.3 kΩ,C=0.1 μF. Calculate
the free running frequency. (AU ND 2012)
f =1.07 kHz
13. Why VCO is called voltage to frequency converter? (AU ND 2012)
The VCO provides the linear relationship between the applied voltage and the oscillation
frequency. Applied voltage is called control voltage. The control of frequency with the help
of control voltage is also called voltage to frequency conversion. Hence VCO is also called
voltage to frequency converter.
14. In what way VCO is different from other oscillators. (AU MJ 2012)
To adjust the output frequency to match (or perhaps be some exact multiple of) an
accurate external reference.
Where the oscillator drives equipment that may generate radio-frequency interference,
adding a varying voltage to its control input can disperse the interference spectrum to
make it less objectionable. See spread spectrum clock.
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15. Mention any two applications of 555 Timer in Monostable mode.
The applications of IC555 timer in mono stable mode are
i. Frequency divider
(AU MJ 2012)
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iii.
Pulse width modulation
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Missing pulse detector
iv. Linear ramp generator
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16. What are one, two and four quadrant multipliers? (AU ND 2011)
In one quadrant multiplier the polarities of both the inputs must always be positive.
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A two quadrant multiplier functions properly if one input is held positive and the
other is allowed to swing in both positive and negative.
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If both the inputs are allowed to swing in both positive and negative directions, the
operation is four quadrant multiplier operations.
17. List the applications of NE 565.
rin (AU ND 2010)
The applications of NE 565 are
i. Frequency multiplier g.n
ii. Frequency synthesizer
iii. FM detector
iv. FM Demodulator is the applications of NE565.
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18. Mention any two application of multiplier IC. (AU ND 2010)
The multiplier is used for
i. Frequency shifting
ii. Voltage divider
iii. Measurement of real power
iv. Detecting phase-angle difference between two signals of equal frequency
v. Multiplying two signals
19. Draw the relation between the capture range and lock range relationship in a PLL.
(AU ND 2010)
20. Enlist the important features of 555 timer circuit . (AU ND 2009)
The features of 555 timer circuit are,
i. It has two basic operating modes: monostable and astable
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iii. It has very high temperature stability.
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21. Determine the output pulsewidth of the monostable amplifier using 555 timer if
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R=10kΩ and C=0.01µF.
C=T/1.1R
(AU ND 2009)
T=1.1RC
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T=1.1x10000x0.01x10-6
T=0.11ms
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22. What are the different stages of operation in a PLL? (AU MJ 2007)
The different stages of PLL are
i. Free running
ii. Capture
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iii. Locked/ tracking
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23. What is a function of reset in 555 timer?
g.n (AU MJ 2006)
555 timer is an interrupt for the timing device when pin 4 is grounded; it resets the timer
output to low level irrespective of the input conditions.
24. Define the PULL time of PLL. et
(AU ND 2006)
The total time taken by the PLL to establish lock is called pull-in time. It depends on the
initial phase and frequency difference between the two signals as well as on the overall loop
gain and loop filter characteristics.
25. List the applications of 555 timer in Astable mode of operation. (AU ND 2006)
The applications of 555 timer in Astable modes are,
FSK generator
Pulse-position modulator
PART-B
1. With the help of schematic diagram, explain the operation of IC 566 VCO and derive its
output frequency. (13)(AU ND 2016)
2. What is PLL? How frequency multiplication is done in PLL? (13)(AU ND 2016)
3. With neat diagram, explain the operation of four quadrant variable transconductance
multiplier circuit. (16)(AU ND 2015)
4. Explain with functional block diagram the operation of 566 voltage controlled oscillator.
Also determine the maximum and minimum output frequencies in the circuit shown
below. (10+6)(AU ND 2015)
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5. Explain the operation of an astable multivibrator configured around 555 timer IC and
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derive and derive an expression for output frequency with neat illustration.
(16)(AU ND 2014)
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6. (i) Draw the functional block diagram and explain the characteristics of IC555.
(ii)Write a short note on analog multiplier. (8+8)(AU MJ 2014)
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7. (i)Explain the functioning of IC566 as a PLL.
(ii)Explain the applications of PLL as a frequency translator.
(12)(AU MJ 2014)
(4)(AU ND 2014)
18. Draw the symbol of analog multiplier IC and write expression for V0.List the
applications and explain any two. (8)(AU ND 2007)
19. Define the voltage to frequency converting factor and derive its expression. List the
applications of VCO. (8)(AU ND 2007)
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UNIT V
APPLICATION ICs
PART-A
1. What is SMPS? (AU ND 2016)
A Switched-Mode Power Supply (SMPS) is an electronic circuit that converts power using
switching devices that are turned on and off at high frequencies, and storage components
such as inductors or capacitors to supply power when the switching device is in its non-
conduction state.
2. What are the applications of fixed voltage regulators? (AU ND 2016)
The applications of fixed voltage regulators are
i. Low current consumption
ii. Overvoltage/ Short-circuit protection
iii. Reverse polarity protection
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3. What is meant by thermal shutdown applied to voltage regulators?
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(AU ND 2015)
Thermal shutdown protection is very much necessary because due to self heating it is
possible that the series pass element may get damaged permanently. Such a protection
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prevents the junction temperature to rise above a safe limiting value. This limiting safe
value of junction temperature is 1750C or less.
In this protection scheme, the junction temperature of the series pass element is sensed. By
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sensing this, its power dissipation is reduced till its temperature drops to a safe value.
4. Draw the internal block diagram of a function generator IC. (AU ND 2015)
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5. State the need for protection diodes in voltage regulators based on LM317
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regulators. (AU ND 2014)
Protection diodes in voltage regulators based on LM317 regulators are
recommended for output voltages in excess of 25 V or high capacitance values (CO > 25 F,
CAdj > 10 F). Diode D1 prevents CO from discharging through the IC during an input short
circuit. Diode D2 protects against capacitor CAdj discharging through the IC during an output
short circuit. The combination of diodes D1 and D2 prevents CAdj from discharging through
the IC during an input short circuit.
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9. Define load regulation. nee (AU ND 2013)
Load regulation is defined as the change in output voltage for a change in load current and
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is also expressed in millivolts or as a percentage of the output voltage. Typical value of load
regulation for 7805 is 15 mV for 5mA < I0 < 1.5 A.
10. How to define opto-coupler? g.n (AU ND 2013)
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11. An opto coupler, also called opto-isolator, is an electronic component that transfers an
electrical signal or voltage from one part of a circuit to another, or from one circuit to
another, while electrically isolating the two circuits from each other. It consists of an
infrared emitting LED chip that is optically in-line with a light-sensitive silicon
semiconductor chip, all enclosed in the same package. The silicon chip could be in the form
of a photo diode, photo transistor, photo Darlington, or photo SCR.
The combined package of a LED and a photodiode is called an opto coupler. It is also called
an opto isolator or an optically coupled isolator.
12. What is the principle of switch mode power supplies? (AU MJ 2013)
A switched-mode power supply (switching-mode power supply, SMPS, or switcher) is an
electronic power supply that incorporates a switching regulator to convert electrical power
efficiently. Like other power supplies, an SMPS transfer’s power from a source, like mains
power, the pass transistor of a switching-mode supply continually switches between low-
dissipation, full-on and full-off states, and spends very little time in the high dissipation
transitions, which minimizes wasted energy. Ideally, a switched-mode power supply
dissipates no power.
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saturation region there is negligible voltage drop across it hence the power dissipation is
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almost zero.
16. What are the disadvantages of linear voltage regulators?
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The disadvantages of linear voltage regulators are
(AU ND 2011)
The input step down transformer is bulky and the most expensive component of
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the linear regulated power supply mainly because of low line frequency.
Because of the low line frequency, larger values of filter capacitors are required
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to decrease the ripple.
The efficiency of a series regulator is very low.
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17. How will you increase the output of a general purpose op-amp? (AU MJ 2010)
A simple method of increasing the output current of a general purpose op-amp is to connect
a power booster circuit in series with the op-amp.
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18. Using LM380 draw the circuit for audio power amplifier.
g.n (AU MJ 2010)
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19. List the important parts of regulated power supply. (AU ND 2010)
The parts of regulated power supply are
Reference voltage circuit
Error amplifier
Series pass transistor
Feedback network
Downloaded From : www.EasyEngineering.net
Downloaded From : www.EasyEngineering.net EE 8451 Linear Integrated Circuits and Applications
20. What are the advantages of switch mode power supplies? (AU ND 2010)
The advantages of switch mode power supplies are
Smaller size
Lighter weight (from the elimination of low frequency transformers which have a
high weight)
Lower heat generation due to higher efficiency.
21. Draw the circuit diagram of an IC opto coupler. (AU MJ 2009)
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By using suitable switching loss reduction technique, the switching frequency can be
increased so as to reduce the size and weight of the inductors and capacitors.
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23. Draw the circuit of LM317 voltage regulator, give the expression for V0.
(AU ND 2007)
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The voltage that the adjustable regulator outputs is determined by the equation below
Vout = Vref (1 + RL/RH)
VOUT=1.25(1+R2/R1)+Iadj(R2)
24. What is the need for current limiting in regulated power supplies? (AU ND 2007)
Current limiting in regulated power supplies is refers to the ability of a regulator to prevent
the load current from increasing above a preset value.
25. What are the drawbacks of simple current limiting and how is it overcome?
(AU MJ 2007)
The disadvantages of constant current limiting are relatively large power dissipation in the
series pass transistor when load terminals are shorted. Thus a large power rating transistor
is required.
The power dissipation in the series pass transistor is given by
PD= (Vin-VBE) ISL
Where VBE =base –emitter voltage of Q1
26. Write the function of opto coupler. Mention any one of its application. (AU ND 2006)
Functions :
To isolate one section of a circuit from another, each section having different signal voltage
levels to ensure compatibility between them. To prevent electrical noise or other voltage
transients that may exist in a section of a circuit from interfering with another section when
both sections have a common circuit reference. Noise or voltage transients can be caused by
a poor printed circuit board layout.
Applications :
Common applications for optocouplers include microprocessor input/output switching, DC
and AC power control, PC communications, signal isolation and power supply regulation
which suffer from current ground loops, etc.
In this application, the optocoupler is used to detect the operation of the switch or another
type of digital input signal. This is useful if the switch or signal being detected is within an
electrically noisy environment. The output can be used to operate an external circuit, light
or as an input to a PC or microprocessor.
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27. Differentiate between linear and switching regulators.
Linear regulations Switching regulations
(AU ND 2006)
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the active region as a linear devices as
switching devices.
1. The series pan transistor operator
either at cut-off or at saturation.
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2.Since the pass transistor is always in the 2.Power dissipation is less
active region, power dissipation is more.
3.The efficiency is less .
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28. Mention the advantages of opto-couplers.
3.The efficiency is more.
(AU MJ 2006)
The advantages of opto-couplers are
Better isolation between the two stages. nee
Impedance problem between the stages is eliminated.
Wide frequency response. rin
Easily interfaced with digital circuit.
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Compact and light weight.
Problems such as noise, transients, contact bounce, are eliminated.
29. Why current boosting is done in 723 regulators?
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(AU MJ 2006)
The 723 regulator can give adjustable output voltage in a wide range. It provides short
circuit protection and current feedback using external components. The basic regulator can
be current boosted with an external pass transistor.
Iload=βpass transistor x Io(723)
PART-B
1. What do you mean by the fixed voltage and variable voltage regulator? List its various
applications. (13)(AU ND 2016)
2. Write short notes on
(i) LM380 Power Audio Amplifier. (6)(AU ND 2016)
(ii) ICL 8038 Function Generator (7)(AU ND 2016)
3. State the advantages of IC voltage . Explain the feature and internal structure of general
purpose linear IC723 regulator. Design a regulator using IC 723 to meet the following
specifications: V0=5V; I0=100mA ;Vin =15±20% ;Isc=150mA ;Vsence=0.7V. (8)(AU ND 2014)
4. With a neat diagram, explain the working of step down switching regulator.
(8)(AU ND 2014)
5. With a neat functional diagram, explain the operation of LM380 power amplifier.
(8)(AU ND 2014)-2
6. Explain the operation of SMPS with neat diagrams. (8)(AU ND 2014)-2
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7. Design a voltage regulator using IC723 regulator to satisfy the following specifications.
(i)V0=12V,
(ii) I0=500mA
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(iii) Vin= 18±20%,
(iv)Isc=600mA
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(v)Vsence=0.7V. Give the complete schematic diagram. (Assume and justify if any data
required)
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8. Discuss in detail the operation and applications of the following circuits.
(16)(AU MJ 2014)
(ii) Optocoupler
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9. What are IC voltage regulators? Explain the principle of operation of IC LM317 as a voltage
regulator.
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10. Draw and explain the functional diagram of 723 general purpose regulators and make the
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necessary changes to make it as low voltage regulator and high voltage regulator.
(16)(AU ND 2013)
17. (i) Briefly explain protection circuits in voltage regulators. (8)(AU ND 2009)
(ii) Write short note on LM 380 audio power amplifier. (8)(AU ND2009)
18. Draw the circuit diagram and explain the operation of any one negative voltage regulator.
(8)(AU ND 2009)
19. Discuss on the different types of three terminal voltage regulators. (8)(AU ND 2009)
20. Draw the circuit diagram of IC723 based positive voltage regulator, to give +8V output at
200mA .Incorporate short circuit protection current limit circuit to operate at 400mA . Find
all resistor values, calculate their wattage and specify the types of resistors.
(8)(AU ND 2006)
________________________
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