| Post Name | LECTURER IN ELECTRONICS ENGINEERING (GOVT. POLYTECHNIC COLLEGES) |
|---|---|
| Question Paper Code | 108/2025 |
| Category Code | 720/2024 |
| Date of Test | 29 August 2025 |
| Medium of Question | ENGLISH |
| Exam Type | OMR Examination |
| Total Questions | 100 |
1
Which of the following semiconductor material is used in the manufacture of white light
emitting LEDs?
Answer
D. Indium Gallium Nitride
2
Which of the following devices is an active device?
Answer
A. Field effect transistor
3
Rectification efficiency of a centre tap rectifier is:
Answer
C. 81.2%
4
Band gap energy of Silicon at 300 K temperature is :
Answer
C. 1.12 eV
5
An inverter :
Answer
B. Converts DC to AC
6
Which of the following semiconductor material is most widely used in the manufacture of
VLSI circuits?
Answer
C. Silicon
7
Which of the following Batteries have the highest gravimetric energy density?
Answer
B. Lithium Ion Battery
8
A charged lead acid cell functions as
Answer
B. Independent voltage source
9
8051 microcontroller has a _____________ wide address bus.
Answer
A. 16 bit
10
8051 microcontroller has _____________ of read only memory.
Answer
D. 4 KB
11
GSM mobile technology uses :
Answer
C. Both TDMA and FDMA
12
Which of the following frequency band is used for commercial mobile cellular
communication?
Answer
B. UHF band
13
In a voltage regulator circuit using a Zener diode with a 9V breakdown voltage, a
300 Ω series resistor, and a 15V input voltage, what is the current flowing through the
Zener diode when the load resistance is 900 Ω ?
Answer
C. 10 mA
14
Why is a cascode amplifier
Answer
C. Reduced Miller effect
15
In a multistage amplifier, what is the main advantage of using staggered tuning over
identical tuning?
Answer
B. Wider bandwidth
16
In a transistor amplifier, which configuration provides the highest input impedance?
Answer
D. Darlington Pair
17
What is the primary advantage of a Class AB power amplifier over a Class B amplifier?
Answer
B. Reduced crossover distortion
18
Why is a crystal oscillator preferred in precision applications compared to LC oscillators?
Answer
B. Better frequency stability
19
An NPN BJT with a current gain ( β ) of 100 is used as a switch. In which two regions
does it primarily operate, and what is a condition that could cause it to enter the active
region, increasing power dissipation?
Answer
C. Cutoff and saturation; insufficient base current I B < C
β
20
For a Class A amplifier, the quiescent collector current is I꜀Q = 120 mA and the supply voltage is V꜀꜀ = 10 V. What is the maximum AC power output, assuming it is resistively loaded with the Q-point centered?
Answer
C. 0.3 W
21
A multistage amplifier consists of three identical stages, each with a gain of 10. What is
the total gain in dB?
Answer
B. 60 dB
22
A Darlington pair is formed with two transistors Q1 and Q2 with current gains
60 and 80 respectively. If the base current of Q1 is 10 μ A, what is the emitter current
of Q2?
Answer
B. 49.41 mA
23
A common-source FET amplifier with an n-channel MOSFET has gₘ = 4 mS, Rᴅ = 3 kΩ and Rₛ = 0.5 kΩ, with no bypass capacitor. Calculate the low-frequency voltage gain Aᵥ.
Answer
B. −4
24
A Colpitts oscillator uses two capacitors of 2000 pF each and an inductor of 2 mH. What
is the oscillation frequency?
Answer
Question Cancelled
25
An RC phase shift oscillator with three identical RC stages uses an inverting amplifier
with a gain of −30. Each stage has R = 10 kΩ and C = 10 nF. What is the total phase
shift provided by the three RC stages at the oscillation frequency?
Answer
A. 180°
26
In a full-wave rectifier circuit with a capacitor filter, the input is a 50 Hz sine wave. If the load resistance is 1 kΩ and the filter capacitor is 100 μF, what is the approximate ripple factor? (Given 1/√3 ≈ 0.577)
Answer
A. 0.024
27
What is the primary advantage of using a tunnel diode in high-frequency circuits
compared to a standard PN junction diode?
Answer
B. Negative resistance region
28
Why is a Class D amplifier preferred in modern portable devices over a Class A
amplifier?
Answer
B. Greater efficiency
29
What is the main advantage of a Wien bridge oscillator over an RC phase shift oscillator?
Answer
D. Greater amplitude control
30
Which characteristic of a bistable multivibrator makes it suitable for memory
applications?
Answer
C. Two stable states
31
A three-stage BJT amplifier must handle signals from 0Hz to 100 kHz. Which of the
following coupling method is suitable for this amplifier?
Answer
C. Direct coupling
32
Why is a MOSFET preferred over a JFET in digital switching applications?
Answer
B. No gate current requirement
33
Which of the following is not an ideal characteristics of an opamp?
Answer
D. Zero slew rate
34
Virtual ground concept occurs in :
Answer
A. Inverting amplifier
35
Type of negative feedback used in an inverting amplifier is :
Answer
B. Voltage shunt
36
741 opamp has a slew rate of 0.5 V/us. What is the maximum frequency an input
sinusoid of peak value 5V at which distortion sets in due to slew rate limitation?
Answer
C. 15.92 KHz
37
Unity Gain-bandwidth of 741 opamp is 1MHz. A non-inverting amplifier which uses
741 opamp having a voltage gain of 40 dB will exhibit a –3dB bandwidth of :
Answer
C. 10 kHz
38
For the opamp circuit shown in figure below, Vo is:
Answer
A. –2V
39
Consider the Schmitt trigger shown in the figure. The inverting input is driven by Vᵢₙ; the non-inverting input is connected to ground through R₁ and to output Vₒ through R₂. R₁ = R₂ = 5 kΩ and the saturation voltage is ±10 V. The hysteresis voltage is:
Answer
C. 10 V
40
A comparator with zero reference voltage is called as :
Answer
A. Zero crossing detector
41
The output amplitude of an opamp astable multivibrator can be limited by the use of :
Answer
C. zener diodes
42
The output voltage Vₒ of the differential amplifier shown is sought for V₁ = 2 V and V₂ = 4 V. The source diagram has V₁ connected through 5 kΩ to the inverting input with 10 kΩ feedback; V₂ is connected through 5 kΩ to the non-inverting input, which also has 5 kΩ to ground.
Answer
C. 2 V
43
Which of the following is a requirement for an instrumentation amplifier?
Answer
D. High gain stability and high CMRR
44
The pass band gain of a second order butterworth filter is :
Answer
D. 1.586
45
The cut-off frequency and pass-band gain of the shown active filter are requested. The source circuit has a 0.01 μF input capacitor, a 7.95 kΩ resistor to ground at the non-inverting input, and equal 10 kΩ gain-setting resistors.
Answer
B. Cut-off frequency = 2 kHz and pass-band gain = 2
46
The centre frequency of a PLL is determined by the free-running frequency of :
Answer
B. VCO
47
A 555 monostable multivibrator has R = 1000 kΩ and time delay T = 11 s. The value of capacitance C is:
Answer
D. 10 μF
48
A 555 timer in monostable application mode can be used as
Answer
C. Frequency divider
49
Low frequency gain in an opamp integrator is limited by adding
Answer
D. a resistor connected across the feedback capacitor
50
A non-inverting amplifier with gain unity is known as
Answer
B. voltage follower
51
What is the feedback element of a logarithmic amplifier?
Answer
C. a diode
52
Wienbridge oscillator employs opamp as
Answer
A. non-inverting amplifier
53
Which code turns into its 9’s complement if you switch all the 0’s to 1’s and 1’s to 0’s?
Answer
D. Excess 3 code
54
The number of digit 1 present in the binary representation of
4 × 256 + 6 × 32 + 1 × 16 + 3 × 2 + 1 is :
Answer
C. 7
55
A seven-bit hamming code is received as 1111101. What is the correct code?
Answer
D. 1111111
56
An industrial plant has 3 sensors for monitoring machines P, Q and R. The alarm system
should activate only when at least 2 machines are running simultaneously. The Boolean
expression for the alarm control logic is :
Answer
D. PQ + PR + QR
57
If only the logic inputs X and Y are available (their complements X and Y are not
provided), what is the minimum number of two-input NAND gates needed to realise the
Boolean function X ⊕ Y ?
Answer
A. 4
58
Which digital circuit component can function as a parallel-to-serial converter?
Answer
C. Multiplexer with counter
59
Which one of the following statements is not correct?
Answer
A. In a ripple carry counter, the addition time remains constant regardless of
the number of bits
60
A 4-bit Johnson Counter is initialised to 0000 and operates with a synchronous clock.
What is the number of binary states that do not appear in its standard cycling sequence?
Answer
B. 8
61
A flip-flop is
Answer
D. Sequential Logic circuit and edge sensitive
62
A ROM will be utilized to create a “squarer” that produces the square of a 4-bit number.
What should the size of the ROM be?
Answer
C. 4 address lines and 8 data lines
63
Which logic families can function with a supply voltage ranging from 3V to 15V?
Answer
B. CMOS
64
The output voltage of a 5-bit digital-to-analog converter
Answer
C. 8.125 V
65
The time taken for conversion in a 10-bit successive approximation A/D converter,
operating at a clock frequency of 1 MHz is :
Answer
A. 10 μs
66
In the 8086 architecture, which of the following registers does not qualify as a segment
register?
Answer
C. IP
67
Which of the following 8086 instructions is utilized for unconditional branching?
Answer
B. CALL
68
A serial communication system employs an 8251 USART (Universal
Synchronous/Asynchronous Receiver/Transmitter) operating in asynchronous mode,
featuring 8 data bits, 1 stop bit, and no parity. What is the least number of control words
required to be written to the 8251 to set it up for this operation?
Answer
B. 2 (Mode word and Command Word)
69
Which of the following operational modes for the 80286 processor ensures backward
compatibility with the 8086/8088 and utilizes real memory addresses?
Answer
A. Real Address Mode
70
What is the typical number of external hardware interrupt sources found in the basic
8051 microcontroller?
Answer
B. 2
71
Which instruction of the 8051 is utilized to execute a bit-wise OR operation between the
Accumulator and a direct address (either SFR or internal RAM)?
Answer
D. ORL A, direct
72
If the Program Status Word (PSW) register of the 8051 holds the value D0H, what conclusions can be drawn regarding the chosen Register Bank as well as the status of the Auxiliary Carry Flag (AC) and Carry Flag (CY)?
Answer
D. Register Bank 2 selected, CY = 1, AC = 1
73
Which of the following is a property that the LTI systems follow?
Answer
D. All of the above
108/2025 13 A
74
As per the Shannon’s theorem, the channel capacity C is given by the formula
_____________
Answer
B. C = B × log₂(1 + S/N)
75
The standard baud rate used in modern serial communications for high-speed data
transfer is _____________
Answer
Question Cancelled
76
If R is the radius of the Earth, which is the correct equation used to estimate the distance d to the horizon when viewing from a height h?
Answer
A. d = √(2hR)
77
The earth’s stratosphere range is approximately between _____________ and
_____________ Kms.
Answer
B. 15 and 50 Kms
78
For an AM wave, if Pₜ is the transmitting power, P꜀ is carrier power and m is the modulation index, then Pₜ is given by:
Answer
C. Pₜ = P꜀(1 + m²/2)
79
In an AM superheterodyne receiver, the intermediate frequency IF is _____________
Answer
A. 455 KHz
80
In the _____________ modulation technique the minimum channel bandwidth is used.
Answer
B. SSB-SC
81
A pre-emphasis circuit is essentially a _____________ and a de-emphasis circuit in FM
system a _____________
Answer
D. high pass filter, low-pass filter
82
Which of the following is not a property of the Discrete Fourier Transform?
Answer
B. Asymmetry property
83
Among the following, satellite TV Dish uses _____________ antenna.
Answer
D. Parabolic reflector
84
In interlaced scanning technique, the scanning takes place on ______________________
Answer
B. odd and even lines of an image in separate passes
85
The PAL (Phase Alternating Line) color encoding system in analog television
broadcasting is characterized by _____________
Answer
C. 625 lines per frame, 50 Hz field refresh rate
86
For long-distance optical communication, _____________ band is used because the
attenuation of light is minimal in this range.
Answer
Question Cancelled
87
In digital modulation techniques, the QPSK stand for
Answer
A. Quadrature Phase Shift Keying
88
The cellular CDMA uses the frequency band of _____________
Answer
A. 824 MHz to 894 MHz
89
TRAPATT diode stands for ______________
Answer
B. Trapped Plasma Avalanche Triggered Transit Time diode
90
In the RADAR range equation, the range is _____________.
Answer
C. directly proportional to the fourth root of the transmitted power
91
An SCR is used in a resistive half-wave rectifier circuit. The SCR is triggered at an angle α = 45° in every positive half-cycle. The input is a sinusoidal voltage, and the resulting current waveform is: • Zero from 0 to α. • Follows the sine shape from α to π. • Zero during the entire negative half-cycle. If the peak current is I_m, compute the RMS value of the current.
Answer
D. (I_m/√2) × √(3/8 + 1/(4π))
92
A UJT-based relaxation oscillator is used to trigger an SCR at a firing frequency of
1 kHz. The intrinsic stand-off ratio (η ) of the UJT is 0.9, and the time constant of the
charging circuit is given as τ = 40 R nanoseconds, where R is the charging resistor in
ohms.
Compute the value of R. :
Answer
A. 10.85 kΩ
93
A phototransistor operates under an ambient radiant flux density of 5 mW/cm². The source graph plots photo-induced base current Iᴮ (μA) against radiant flux density (mW/cm²), passing through approximately (0,0), (3,5), (5,8) and (8,12). Assuming DC current gain hꜰᴇ = 40, calculate collector current:
Answer
B. 0.32 mA
94
Which of the following statements about the DIAC are correct?
1. A DIAC is a bidirectional device that conducts current only after its breakover
voltage is reached.
2. DIAC can be called as a gateless triac
3. DIAC has symmetrical breakdown characteristics
Answer
D. All the above Statements are correct
95
In a cathode ray tube (CRT) used for precision beam control in oscilloscopes, electrons are emitted from a heated cathode and accelerated through a potential difference of 810 V before entering the deflection system. Find the electron velocity on leaving the accelerating anode. Take electron charge q = 1.6 × 10⁻¹⁹ C and electron mass m = 9.11 × 10⁻³¹ kg.
Answer
D. 16.8 × 10⁶ m/s
96
A 3½-digit multimeter has a specification of ±(1.0% + 5 counts) and is measuring 15.00 V on the 20 V range. What is the total error?
Answer
C. ± 0.20 V
97
An analog multimeter rated at 20 k Ω /V sensitivity is used to measure a DC voltage
across a load. If the multimeter is set to the 10 V range, which of the following best
represents the input resistance presented by the meter to the circuit during this
measurement?
Answer
B. The multimeter offers a parallel resistance of 200 k Ω across the load
98
A LCD panel has a resolution of 1280 × 720 pixels. Each pixel consists of 3 subpixels
(Red, Green, Blue), and each subpixel uses an 8-bit color depth. If one full frame is stored
in memory without compression, what is the total memory required to store one frame,
in megabytes (MB)?
Answer
A. 2.63 MB
99
Which of the following is correct for LCD (Liquid Crystal Display) technology compared
to other flat-panel display technologies?
Answer
B. Inability to emit light; requires external illumination
100
Which of the following statements best highlights a fundamental operational distinction
between a laser diode and a Light Emitting Diode (LED) in optoelectronic systems?
Answer
C. Laser diodes require optical feedback and population inversion to achieve
stimulated emission
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