Questions

https://testbook.com/TS-csir-net/tests/67051f939766740c5321bee2?attemptNo=1#/lt-solutions

Question 1 ( 10 pts )

A high-frequency voltage signal Vi = Vm sin ωt is applied to a parallel plate deflector as shown in the figure.

An electron beam is passing through the detector along the central line. The best qualitative representation of the
intensity I(t) of the beam after it goes through the narrow circular aperture D, is
Question 2

A receiver operating at 25◦ has an input resistance of 100 Ω. The input thermal noise voltage for this receiver with a
bandwidth of 100 kHz is closest to
1. 0.4 nV

2. 0.6 pV
3. 40 mV
4. 0.4 µV

Question 3

An amplifier with a voltage gain of 40 dB without feedback is used in an electronic circuit. A negative feedback with a
fraction 1/40 is connected to the input of this amplifier. The net gain of the amplifier in the circuit is closest to
a. 40 dB

b. 37 dB
c. 29 dB
d. 20 dB

Question 4

The figure below shows a circuit with two transistors, Q1 and Q2 . having current gains β1 and β2 respectively.

The collector voltage V will be closest to

a. 0.9 V
b. 2.2 V
c. 2.9 V

d. 4.2 V

Question 5

The circuit containing two n-channel MOSFETs shown below works as

 1. a buffer
2. a non-inverting amplifier
3. an inverter

4. a rectifier

Question 6

Four students (S1 ,S2 ,S3 , and S4 ) make multiple measurements on the length of a table. The binned data are plotted
as histograms in the following figures

If the length of the table, specified by the manufacturer, is 3m, the student whose measurements have the minimum
systematic error is
1. S2
2. S1

3. S4
4. S3

Question 7

A high impedance load (network) is connected in the circuit as shown below

a.

b.
 c.

d.

Question 8

An elastic rod has a low-energy state of length L and a high-energy state of length L. The best schematic representation
of the temperature (T) dependence of the mean equilibrium length L(T) of the rod is
Question 9

In the circuit shown below, the gain of the op-amp at the midpoint of its bandwidth is 105 .A sinusoidal voltage with
angular frequency ω = 100 rad/s is applied to the input of the op-amp.

Question 10

A rod pivoted at one end is rotating clockwise 25 times a second in a plane. A video camera that records at a rate of 30
frames per second is used to film the motion. To someone watching the video, the apparent motion of the rod will seem
to be
1. 10 rotations per second in the clockwise direction

2. 10 rotations per second in the anticlockwise direction

3. 5 rotations per second in the clockwise direction
4. 5 rotations per second in the anticlockwise direction

Question 11

The I-V characteristics of the diode D in the circuit below are given by
 qV 
Is = e k B T − 1

where Is is the reverse saturation current, visthevoltageacrossthediode, andT is the absolute temperature.

If the input voltage is Vin , then the output voltage Vout is

 
a. Is R ln qV in
kB T + 1
 
kB T q(Vin +Is R)
b. q ln kB T
 
kB T Vin
c. q ln Is R +1
 
d. − kBq T ln Vin
Is R +1
Question 12

Two voltmeters A and B with internal resistances 2 M Ω and 0.1 kΩ are used to measure the voltage drops VA and VB ,
respectively, across the resistor R in the circuit shown below.

VA
The ratio VB is

Question 13

In the 3-bit register shown below, Q and Q are the least and the most significant bits of the output, respectively

If Q1 ,Q2 , and Q3 are set to zero initially, then the output after the arrival of the second falling clock (CLK) edge is

1. 001
2. 100
3. 011
4. 110

Question 14

A 10 V battery is connected in series to a resistor R and a capacitor C, as shown in the figure.

The initial charge on the capacitor is zero. The switch is turned on, and the capacitor is allowed to charge to its full
capacity. The total work done by the battery in this process is
1. 10−3 J
2. 2 × 10−3 J

3. 5 × 10−4 J
4. 47 × 10−2 J
Question 15

In the circuit shown below, the input voltage (in volts) is given by

Vin (t) = 0.1 sin(ω1 t) + sin(ω2 t)

where ω1 = 5 × 102 s−1 and ω2 = 5 × 104 s−1

The time-varying part of the output voltage Vout (in volts) closest to
1. −0.2 sin(ω1 t) − 2 sin(ω2 t)
2. −0.2 sin(ω1 t) + 0.2 cos(ω2 t)
3. 2 cos(ω1 t) + 0.2 cos(ω2 t)

4. 2 cos(ω1 t) − 2 sin(ω2 t)

https://testbook.com/TS-csir-net/tests/6840402141b15f2c64741e2d?attemptNo=1#/lt-solutions
Question 16

An LED is required to glow brightly when the temperature sensed by a Platinum resistance thermometer exceeds a
certain value. In the circuit shown below, the resistance of the Pt thermometer (in ohms) varies as

RP T (T ) = 100 + 0.4T

where T is the temperature in degrees Celsius. The transistor turns on when VBE > 0.7V , and it has a very high current
gain. The temperature at which the LED would start glowing is closest to

1. 850◦ C
2. 400◦ C

3. 500◦ C
4. 700◦ C
Question 17

An ideal inductor L is connected in series to a 1500Ω resistor as shown in the circuit (inset). When the circuit is driven
by a battery B1 , the voltage across the resistor as a function of time, as measured by an oscilloscope, is shown in the
plot

Based on this observation, the estimated value of L is closest to

1. 50 mH
2. 300 mH

3. 450 mH
4. 150 mH

Question 18

A circuit component consists of a resistor in parallel with an ideal current source. The I-V characteristics of the
component were measured using a variable voltage source and an ammeter ’A’

I I
⃝ ⃝
V V

(a) (b)

I I
⃝ ⃝
V V

(c) (d)

Question 19

In the circuit shown below, four silicon diodes and four capacitors are connected to a sinusoidal voltage source of
amplitude Vin > 0.7V and frequency 1 kHz.If the knee voltage for each of the diodes is 0.7 V and the resistances of the
capacitors are negligible, the DC output voltage Vout after 2 seconds of starting the voltage source is closest to
 1. 4Vin − 0.7V

2. 4Vin − 2.8V
3. Vin − 0.7V
4. Vin − 2.8V

Question 20

In the circuit below, there is a voltage drop of 0.7 V across the diode D in forward bias, while no current flows through
it in reverse bias.

If Vin is a sinusoidal signal of frequency 50 Hz with an RMS value of 1 V, the maximum current that flows through the
diode is closest to

Question 21

For the given logic circuit, the input waveforms A, B, C, and D are shown as a function of time

To obtain the output Y as shown in the figure, the logic gate X should be
1. an AND gate
 2. an OR gate
3. a NAND gate
4. a NOR gate

https://testbook.com/TS-csir-net/tests/67051f9c9ed5556f430e1581?attemptNo=1#/lt-solutions
Question 22

In the schematic figure given below, the initial values of the 4-bit shift registers A and B are 1011 and 0010, respectively.
The values at SO and SO after the pulse T are respectively

1. 1110 and 1001

2. 1101 and 1001
3. 1101 and 1100

4. 1110 and 1100

Question 23

If the parameters y and x are related by y = log(x), then the circuit that can be used to produce an output voltage V0
varying linearly with x is

1.

2.

3.
 4.

Question 24

Two data sets, A and B, consist of 60 and 10 readings of a voltage measured using voltmeters of resolution of 1 mV
and 0.5 mV, respectively. The uncertainty in the mean voltage obtained from the data sets A and B is UA and UB ,
respectively. If the uncertainty of the mean of the combined data sets is UAB , then which of the following statements is
correct?
1. UAB < UA and UAB > UB

2. UAB < UA and UAB < UB

3. UAB > UA and UAB < UB
4. UAB > UA and UAB > UB

Question 25

Consider an n-MOSFET with the following parameters: current drive strength K = 60µA/V 2 , breakdown voltage
BVDS = 10V , ratio of effective gate width to the channel length W
L = 5, and threshold voltage Vth = 0.5V .In the circuit
given below, this n-MOSFET is operating in the

1. ohmic region
2. cut-off region
3. saturation region

4. breakdown region

Question 26

The state diagram corresponding to the following circuit is

 1.

2.

3.

4.

Question 27

A sinusoidal signal of peak-to-peak amplitude 1 V and unknown time period is input to the following circuit for 5
5-second duration. If the counter measures a value (3E8)H in hexadecimal, then the time period of the input signal is

1. 2.5 ms
2. 4 ms
3. 10 ms

4. 5 ms

Question 28
P
Which of the following circuits implements the Boolean function F (A, B, C) = (1, 2, 4, 6)?

1.
 2.

3.

4.

Question 29

The I-V characteristics of a device are I = Is [exp( aV

t ) − 1]where T is the temperature and a and I are constants
independent of T and V. Which one of the following plots is correct for a fixed applied voltage V?

1.

2.

3.
 4.

Question 30

The active medium in a blue LED light-emitting diode) It is a GaN and InN alloy. The band gaps of GaN and InN
are 3.5 eV and 1.5 eV, respectively. If the band gap of Gax In1−x N varies approximately linearly with x, the value of x
required for the emission of blue light of wavelength 400 nm is (take hc approx1200 eV-nm)
1. 0.95
2. 0.75
3. 0.50

4. 0.33

Question 31

In the circuit below, the input voltage Vi is 2V, Vcc = 16V ,R2 = 2kΩ and RL = 10kΩ

The value of R required to deliver 10 mW of power across RL is

1. 12kΩ
2. 4kΩ
3. 8kΩ

4. 14kΩ

Question 32

Two sinusoidal signals are sent to an analog multiplier of scale factor 1V −1 , followed by a low-pass filter (LPF)

If the roll-off frequency of the LPF is f = 5 Hz, the output voltage Vout is
1. 5 V
2. 25 V
3. 100 V
 4. 50 V

Question 33

The resistance of a sample is measured as a function of temperature, and the data are shown below
T ◦C 2 4 6 8
The slope of the R vs T graph, using a linear least-squares fit to the data, will be
R(Ω) 90 105 110 115

1. 6Ω/◦ C
2. 4Ω/◦ C

3. 2Ω/◦ C
4. 8Ω/◦ C

Question 34

The state diagram that detects three or more consecutive 1’s in a serial bit stream is

1.

2.

3.

4.

Question 35

In the n-channel JFET shown in figure below, V = -2V, C = 10pF, VDD = +16V , and R = 2 kΩ.
If the drain D-source S saturation current IDSS = 10mA and the pinch-off voltage V - 8 V, then the voltage across
points D and S is

Question 36
1
The gain of the circuit given below is − ωRC

1. between a and b
2. between the positive terminal of the op-amp and ground

3. in series with C
4. parallel to C

Question 37

2 × 4 decoder with an enable input can function as a

1. 4 × 1 multiplexer
2. 1 × 4 demultiplexer

3. 4 × 2 encoder
4. 4 × 2 priority encoder

Question 38

In the following circuit, the input voltage V is such that Vin < Vsat , where Vsat is the saturation voltage of the op-amp.
(Assume that the diode is an ideal one and RLC is much larger than the duration of the measurement.)For the input
voltage as shown in the figure above, the output voltage V is best represented by

1.

Question 39

In the figures below, X and Y are one-bit inputs. The circuit, which corresponds to a one-bit comparator, is