Oral Questions

Sr. Oral Questions CO

No. Mapped
CO1
Experiment 1:- Design, build single stage CS amplifier & verify dc operating
point.
Experiment 2:- Simulate frequency response of single stage CS amplifier
Experiment 3:- Implement current series feedback amplifier & measure Rif,
Rof, Avf & bandwidth
Experiment 14:- Simulate CMOS inverter. (other than syllabus)
1 What is DC Analysis? CO1
DC Analysis calculates the DC operating points of circuits.
2 What are the three different configurations of FET? CO1
● Common source: This FET configuration is probably the most
widely used.
● Common drain: This FET configuration is also known as the
source follower.
● Common gate: This transistor configuration provides a low input
impedance while offering a high output impedance.
3 What are the advantages of FET over BJT? CO1
● One class of FETs (JFETs) generates lower noise than BJTs.
● FETs are more temperature stable than BJTs.
● FETs are generally easier to fabricate than BJTs.
4 How many types of FETS are there? CO1
There are two types of field-effect transistors, the Junction Field-Effect
Transistor (JFET) and the “Metal-Oxide Semiconductor”
Field-Effect Transistor (MOSFET), or Insulated-Gate Field-Effect
Transistor (IGFET).
5 What are the applications of MOSFET? CO1
● It is used as an inverter.
● It can be used in digital circuits.
● MOSFET can be used as a high frequency amplifier.
6 Draw symbol of n-channel and p-channel MOSFET CO1

7 What is the difference between JFET & MOSFET? CO1

1
8 What is meant by biasing? CO1
Biasing is the setting of initial operating conditions (current and
voltage) of an active device in an amplifier.
9 Draw and explain the characteristics of n-channel MOSFET? CO1

10 What are the different regions of operation in n-channel MOSFET? CO1

The triode and cut-off region are used to function as a switch, while,
saturation region is used to operate as an amplifier.
11 Explain Load Line and Modes of Operation of n-channel MOSFET CO1
The load line represents the relationship between current and voltage
in the linear part of the circuit.
For an enhancement-mode, n-channel MOSFET, the three operational
modes are: Cutoff, subthreshold, and weak-inversion mode
12 Name any Non-ideal voltage current characteristics CO1

13 What is the scaling of MOSFET? Why is it used? CO1

MOSFET scaling is the reduction in the parameters. due to reduction
in length of the transistor with the advancement in technology.

2
14 What is AC Analysis? CO1
AC Analysis is used to calculate the small-signal response of a
circuit. In AC Analysis, the DC operating point is first calculated to obtain
linear, small-signal models for all nonlinear components.
15 What is the significance of Rs bypassed circuit over Rs unbypassed circuit? CO1

16 What is trans-conductance? CO1

Transconductance, also infrequently called mutual conductance, is the electrical
characteristic relating the current through the output of a device to the voltage
across the input of a device.
17 What is the significance of coupling and bypass capacitors? CO1
Coupling capacitors are used to decouple ac and dc signals so as not
to disturb the quiescent point of the circuit when ac signals are injected at
the input.
Bypass capacitors are used to force signal currents around elements by
providing a low impedance path at the frequency.
18 What is the effect of shunt capacitance? CO1
Shunt capacitors help ease the lag between the current and voltage
that occurs after an inductive load to the transmission line.
19 Why is gain calculated in dB? CO1
We measure voltage gain in db for high voltage assets ,because for
very high voltage values it is very tough to measure it practically.
20 What is the relation between gain with feedback and without feedback? CO1
The gain of the amplifier with feedback is derived below in the case of a
voltage amplifier with voltage feedback. Without feedback, the input
voltage V′in is applied directly to the amplifier input.
21 Explain CMOS as an inverter. CO1
A CMOS inverter is a field-effect transistor that is composed of a
metal gate that lies on top of an insulating layer of oxygen, which
lies on top of a semiconductor.

22 What is feedback? CO1

In electronics, feedback is defined as the process of returning part of
the signal output from a circuit or device back to the input of that
circuit or device.

23 What are the two types of feedback? CO1

Positive feedback(Regenerative) – If the original input signal and the
feedback signal are in phase, the feedback is called positive feedback.
Negative feedback(Degenerative) – However if these two signals are
out of phase then the feedback is called negative feedback.

24 What are the applications of positive feedback and negative feedback? CO1
There are a lot of them. You can use it in:

● amplifier circuits
● oscillators

3
 ● hysteresis regulation
● power stabilization
● voltage and current control
● current mirrors
● signal shapers
● and many many other circuits

25 What are 4 different topologies in feedback amplifiers? CO1

● Voltage Series Feedback Amplifier.

● Voltage Shunt Feedback Amplifier.
● Current Series Feedback Amplifier.
● Current Shunt Feedback Amplifier.

26 Draw the basic block diagram of amplifier with feedback? CO1

27 Explain sampling network and its types? CO1

Network sampling refers to the observation of a sampled network
from some population or family F of possible networks.In particular,
F can be a family of subnets obtainable from a fixed graph or network G.
In this case, G is usually referred to as the population graph or the
population network.

28 Explain comparator / mixer network and its types? CO1

Mainly there are three types of amplitude comparators viz.:

4
 1. Integrating Comparators,

2. Instantaneous Comparators,

3. Sampling Comparators.

29 What is the de-sensitivity of gain? CO1

30 What are the advantages and disadvantages of negative feedback amplifier? CO1
● The negative feedback reduces the size.
● It has highly stabilized gain.
● It has fewer harmonic distortion.
● It has less phase distortion.
● It has higher fidelity.
● More linear operation.
● It has less frequency distortion.
● Input-output impedances can be modified as desired.

Experiment 5:- Design & implement an adjustable voltage regulator using CO2
three terminal voltage regulator IC.

31 Draw block diagram of power supply. CO2

32 Explain each block in detail. CO2

Step Down Transformer

5
 A step down transformer will step down the voltage from the ac mains to
the required voltage level. The turn’s ratio of the transformer is adjusted
so as to obtain the required voltage value. The output of the transformer
is given as an input to the rectifier circuit.

Rectification

Rectifier is an electronic circuit consisting of diodes which carries out the

rectification process. Rectification is the process of converting an
alternating voltage or current into corresponding direct (DC) quantity. The
input to a rectifier is ac whereas its output is unidirectional pulsating DC.
Usually a full wave rectifier or a bridge rectifier is used to rectify both the
half cycles of the ac supply (full wave rectification). Figure below shows a
full wave bridge rectifier.'

DC Filtration'

The rectified voltage from the rectifier is a pulsating DC voltage having

very high ripple content. But this is not we want, we want a pure ripple
free DC

Regulation

This is the last block in a regulated DC power supply. The output voltage
or current will change or fluctuate when there is change in the input from
ac mains or due to change in load current at the output of the regulated
power supply or due to other factors like temperature changes. This
problem can be eliminated by using a regulator.

33 What is Load Regulation? CO2

Load regulation is the measure of the ability of a power supply to maintain a
constant output voltage despite changes in output current or load.

34 What is Line Regulation? CO2

Line regulation is the ability of a power supply to maintain a constant output
voltage despite changes to the input voltage, with the output current drawn from the
power supply remaining constant.

35 What is Ripple Rejection? CO2

Ripple Rejection is the ability of an amplifier to maintain accurate
output voltage despite AC fluctuations in the power supply.

36 What is a voltage Regulator? CO2

A voltage regulator is a component of the power supply unit that ensures a steady
constant voltage supply through all operational conditions

6
37 What are the types of voltage Regulator? CO2
There are two types of voltage regulator
1.Linear Voltage regulator
2.Switching Voltage regulator

38 What is difference between a fixed and adjustable voltage Regulator? CO2

Adjustable Voltage regulators require a very few external components to
achieve its operation.
Fixed voltage regulators require almost no external components (may be
a couple of bypass capacitors). At low cost you have a wide range of
voltage and current selection.

39 What is an adjustable voltage Regulator? CO2

An Adjustable Voltage Regulator is a regulator that can output adjustable
voltages from anywhere in the range that the voltage regulator is
designed to output

40 Draw the circuit diagram of adjustable voltage using LM317. Explain in detail. CO2

The LM317 Voltage Regulator has 3 pins. Below is the pinout:

7
 Looking from the front of the voltage
regulator, the first pin (on the left) is the Adjustable Pin, the middle is Vout, and the last
pin(on the right) is VIN.
VIN- VIN is the pin which receives the incoming voltage which is to be regulated down to
a specified voltage. For example, the input voltage pin can be fed 12V, which the
regulator will regulate down to 10V. The input pin receives the incoming, unregulated
voltage.

Adjustable- The Adjustable pin (Adj) is the pin which allows for adjustable voltage
output. To adjust output, we swap out resistor R2 value for a different resistance. This
creates adjustable voltages.

VOUT- VOUT is the pin which outputs the regulated voltage. For example, the LM317 may
receive 12V as the input and output a constant 10V as output.

41 Explain block diagram of SMPS. CO2

1. The first block is the Bridge rectifier circuit. So the input high
voltage AC supply(230V) is given to the rectifier and it converted
into high voltage DC(230V).

2. Then the unfiltered DC is filtered by the filter circuit.

8
 3. Then the high voltage DC is converted into very high-frequency
square wave AC. Here the high-frequency switch is used to convert
DC to AC. The switch is controlled by the feedback and control
circuit.

4. The high-frequency AC is step down into low voltage( maybe

12V, 6V, etc) by a flyback high-frequency transformer.

5. Then again a rectifier circuit is used to convert the low voltage

AC to DC.

6. A filter circuit is used to filter the DC.

The feedback path and control circuits are used to control the
output DC supply. Mainly the Pulse Width Modulation Circuit is
used for the control circuit.

Experiment 6:- To measure following Op- amp parameters & compare with CO3
specifications given in data sheet. [Any two Practical Op-Amp can be used
for comparison. e.g. LM741, OP07, LF351, LF356, TI071, TI072] a) Input
bias current b) Input offset current c) Input offset voltage d) Slew rate e)
CMRR

42 Draw and explain the pin diagram of LM 741 IC CO3

● Pin 1 is Offset null.

● Pin 2 is the Inverting input terminal.
● Pin 3 is a non-inverting input terminal.
● Pin 4 is negative voltage supply (VCC)
● Pin 5 is offset null.
● Pin 6 is the output voltage.

9
 ● Pin 7 is positive voltage supply (+VCC)
● Pin 8 has no connection.

43 Draw and explain the block diagram of Op-amp CO3

Input Stage: The main function of Op Amp is, at first it creates a

difference between the two input signals and then amplify the
differentiated signal. So in the Input Stage, the differential amplifier
creates the differences.

Intermediate Stage: The output of the input stage is used as the

input of the Intermediate Stage. In this stage, the direct coupling
happens. So, in this stage, the DC voltage is greater than the
ground potential or 0V.

Level Shifting Stage: As in this stage the shifting of voltage level

happens that is why it is called Level Shifting Stage. Here the
emitter follower with a constant current source is applied.

Output Stage: In this stage, the push-pull amplifier is used. The

output of the level shifting stage is given to the input of the
push-pull amplifier. The push-pull amplifier increases the output
voltage and high current delivering capability of the operational
amplifier.

44 Explain the parameters of Op-amp CO3

a. Input offset voltage
With an input offset voltage and a differential input circuit, ideal opamps and
comparators will have an offset voltage of 0V, including error voltage. When
inputting a common-mode (same) voltage to the input pins of an opamp or
comparator, with an ideal opamp no output voltage will be output, but in the case
where an input offset voltage exists, a voltage will be output based on the input
offset voltage
b. Input offset Current

Ideally, the two input bias currents are equal, and thus their difference is zero. In
a practical op-amp, however, the bias currents are not exactly equal.

10
 The input offset current, Ios is the difference of the input bias currents, expressed
as an absolute value.

c. Input Bias Current

You have seen that the input terminals of a bipolar differential amplifier are the
transistor bases and, therefore, the input currents are the base currents.

The input bias current is the dc current required by the inputs of the amplifier to
properly operate the first stage.

d. Differential Input Resistance

e. Common Mode Rejection Ratio
f. Supply voltage Rejection Ratio
g. Large Signal Voltage Gain
h. Output voltage Swing
i. Output Resistance
j. Gain Bandwidth Product
k. Slew Rate

45 Draw and explain the equivalent circuit of an Op-amp CO3

11
 The Circuit which represents op-amp parameters in terms of physical
components, for the analysis purpose is called equivalent circuit of an
op-amp.he Equivalent Circuit of Practical Op Amp shows the op-amp
parameters like input resistance, output resistance, the open loop voltage
gain in terms of circuit components like Rin, Ro etc. The op-amp amplifies
the difference between the two input voltages.Vo = AOL Vd = AOL (V1 – V2)

46 Explain inverting and non-inverting operation of Op-amp CO3

In the case of the inverting amplifier, the output is out of phase wrt input.
Whereas for the non-inverting amplifier, both input and output are in the
same phase. The input signal in the inverting amplifier is applied at the
negative terminal of the op-amp.

47 Draw inverting and non inverting amplifier and derive gain equation CO3

Experiment 7 :- Study and Implementation of Integrator CO3

48 ExAn integrator in measurement and control applications is an element CO3

whose output signal is the time integral of its input signal. It accumulates
the input quantity over a defined time to produce a representative output.
Integration is an important part of many engineering and scientific
applications.plain what is an integrator?

49 Explain what are the applications of integrators? CO3

50 Op-amp is used mostly as an integrator than a differentiator. Explain why? CO3

51 Explain what is an adder or summing amplifier? CO3

52 Explain what is a differential amplifier? CO3

53 Compare the salient feature of an integrator and differentiator using Op-amp. CO3

54 What are the limitations of ideal integrator CO3

55 Draw frequency response of a practical and ideal integrator CO3

56 Why the gain drops by 20db/decade in integrator CO3

57 Draw and explain frequency response of differentiator CO3

58 Draw a subtractor circuit and explain its working CO3

Experiment 8 :- Design and implement 2bit R-2R ladder DAC CO4

12
59 What is output of a DAC or ADC ? Draw it in a graph format and show CO4

60 Calculate output voltage of 4 bit DAC for digital input 10000000 with reference CO4
voltage of 5 V.

61 ADCs sample continuous analog signals over an input voltage range and CO4
convert them into digital representations (words) with resolution equal to
the ADC's number of bits. ... DACs convert digital input code into analog
output signals, essentially providing the opposite function of an
ADC.What is difference between DAC and ADC

62 List various DAC’s CO4

● Weighted Resistor DAC.

● R-2R Ladder DAC.

63 List Different ADC’s CO4

● Successive Approximation (SAR) ADC.

● Delta-sigma (ΔΣ) ADC.
● Dual Slope ADC.
● Pipelined ADC.
● Flash ADC.
64 Explain working of DAC’s and ADC’s CO4

An ADC takes an analog signal and converts it into a binary one, while a
DAC converts a binary signal into an analog value.

65 What are advantages of R-2R DAC over Binary weighted DAC CO4

1) Easier to build accurately as only two precision metal film

resistors are required. 2) Number of bits can be expanded by adding
more sections of same R/2R values. 3) In inverted R/2R ladder DAC,
node voltages remain constant with changing input binary words. This
avoids any slowdown effects by stray capacitances

66 Explain the operation of successive approximation type ADC. CO4

A successive-approximation ADC is a type of analog-to-digital converter

that converts a continuous analog waveform into a discrete digital
representation using a binary search through all possible
quantization levels before finally converging upon a digital output for
each conversion.

13
67 Draw the neat circuit diagram of R-2R ladder DAC and explain its working. CO4

A R-2R resistive ladder network provides a simple means of converting

digital voltage signals into an equivalent analogue output. Input
voltages are applied to the ladder network at various points along its
length and the more input points the better the resolution of the R-2R
ladder.

68 Explain flash type ADC. CO4

Flash Type ADC is based on the principle of comparing analog input

voltage with a set of reference voltages. To convert the analog input
voltage into a digital signal of n-bit output, (2n – 1) comparators are
required. ... The non-inverting inputs of all the three comparators are
connected to the analog input voltage.

69 State the specification of ADC. Also explain the application of ADC CO4

ADC stands for analog to digital converter. It is an electronic device used for
converting an analog signal into a digital signal. The analog input signal of ADC
is continuous time & continuous amplitude signal. The output of ADC is a
discrete time and discrete amplitude digital signal.

70 With the help of a neat diagram explain the operation of Dual slope ADC. CO4

In the dual-slope technique, an integrator is used to integrate an

accurate voltage reference for a fixed period of time. The same
integrator is then used to integrate with the reverse slope, the input
voltage, and the time required to return to the starting voltage is
measured.

14
71 Explain binary weighted register type of DAC CO4

Binary Weighted Resistor DAC consists of an inverting amplifier

op-amp and a string of weighted resistors to distinguish each bit
starting from LSB to MSB position. Each resistor represents a digital
bit to be converted into analog form.

Experiment 9 :-Design, build and test square & triangular wave generator. CO3

72 Draw a square wave generator and explain its working CO3

The square wave generator is defined as an oscillator that gives the

output without any input, without any input in the sense we should give
input within zero seconds that means it must be an impulse input. This
generator is used in digital signal processing and electronic
applications.

73 Explain significance of capacitor in working of Square wave generator CO3

15
 The capacitor starts charging when we have a non-zero input at the
inverting terminal.

74 Draw triangular wave generator and explain its working CO3

First, let us assume that the capacitor is discharged. This makes the inverting

input terminal at a voltage lower compared to the non-inverting input terminal.

This is half the supply voltage from the resistor divider network.The output will

go high till the capacitor voltage goes above half the supply voltage. At this

point, the voltage at the inverting input is greater than the non-inverting input.

Afterward, the output will go low and discharge the capacitor. Simultaneously,

the 10K resistor acts as hysteresis. When the output goes low, the voltage

divider has a 1K and a 10K in parallel, which decreases the overall resistance

and reduces the reference (Vref) voltage. The values of the hysteresis resistor

which is 10K and the resistor divider network both can be changed to increase

or decrease the frequency.

75 What are the applications of square and triangular wave generators CO3

Square and triangular waves are widely used in communication and

control systems.

16
76 Draw the output of a square and triangular wave generator. CO3

The output waveform of the integrator is triangular, if its input is

square wave. Therefore, a triangular wave generator can be obtained
by connecting an integrator at the output of the square wave
generator

Experiment 10 :-Design, build and test Schmitt trigger and plot transfer CO3
characteristics.

77 Why Schmitt trigger is called as regenerative comparator CO3

The circuit is designed with a positive feedback and hence will have
a regenerative action which will make the output switch levels.
Hence it is called a regenerative comparator.

78 Explain working of a Schmitt trigger CO3

A Schmitt trigger makes use of positive feedback – it takes a sample of

the output and feeds it back into the input so as to 'reinforce', so to
speak, the output – which is the exact opposite to negative feedback,
which tries to nullify any changes to the output.

79 How is hysteresis loop formed CO3

When a ferromagnetic material is magnetized in one direction, it will not

relax back to zero magnetization when the imposed magnetizing field is
removed. If an alternating magnetic field is applied to the material,
its magnetization will trace out a loop called a hysteresis loop.

80 Draw an asymmetrical waveform and give it as input to Schmitt trigger and CO3
show its output

81 Explain the working of inverting Schmitt trigger. Also derive the equation for CO3
the trigger points.

An inverter Schmitt trigger is a device that converts any form of an

input signal into a digital output signal, so it can function both with
digital inputs as well as analog.

Experiment 11 CO3
Design, build and test three Op-Amp instrumentation amplifiers for typical
application

82 Explain working of wein bridge Circuit CO3

17
 A Wien bridge oscillator is a type of electronic oscillator that
generates sine waves. It can generate a large range of frequencies.
The oscillator is based on a bridge circuit originally developed by Max
Wien in 1891 for the measurement of impedances.

83 What are the features of an instrumentation amplifier? CO3

Instrumentation amplifiers are precision, integrated operational amplifiers

that have differential input and single-ended or differential output. Some
of their key features include very high common mode rejection ratio
(CMRR), high open loop gain, low DC offset, low drift, low input
impedance, and low noise.

84 In an instrumentation amplifier using transducer bridge, which device measure CO3

the change in physical energy

A resistive transducer is used to measure the change in the same physical

energy, which is connected to one arm of the bridge.

85 Why the instrumentation amplifier has 3 op amps CO3

This circuit provides high input resistance for accurate measurement of

signals from transducers.

A three-op amp in-amp is a commonly-used structure that can amplify

the differential signal while stripping off any common-mode voltage.
An advantage of this circuit is that a single resistor that doesn't need to
be matched with any other resistor in the circuit determines the gain.

86 What are the applications of instrumentation amplifier CO3

An instrumentation amplifier is used to amplify very low-level signals,

rejecting noise and interference signals. Examples can be heartbeats,
blood pressure, temperature, earthquakes and so on.

18