University Grants Commission NET Electronic Science previous year question papers fre

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1. Which diode exhibits negative resistance characteristics ?
(A) Zener (B) Tunnel
(C) Schottky (D) PIN
2. Which crystal structure is preferred to fabricate BJT in VLSI technology ?
(A) <111>
(B) <100>
(C) <110>
(D) None of the above
3. Network contains only independent current sources and resistors. If the values of the
all resistors are doubled, the value of the node voltages will
(A) become half
(B) remain unchanged
(C) become double
(D) be undeterminate
4. A 10 V source is connected in series with a 1 resistor and 1 H inductor and the
switch is closed at t = 0, the current in circuit is
(A) 10 + 10 e100 t (B) 10 – 10 e100 t
(C) 10 + 10 e–100 t (D) 10 – 10 e–100 t
5. A differential amplifier is used at the input stage of an Op Amp to give very high
(A) CMRR (B) Bandwidth
(C) Slew rate (D) Open loop gain

6. What is the current sourcing capacity of 7805 IC voltage regulator ?
(A) 0.5 Amp (B) 2 Amp
(C) 1 Amp (D) 5 Amp
7. Which is the fastest logic family ?
(A) TTL (B) CMOS
(C) RTL (D) ECL
8. The minimum number of NAND gates to implement A + A
–B
+ A
–B
C
(A) Zero (B) 1
(C) 4 (D) 5
9. In which T state of every machine cycle for 8085 does ALE signal become active ?
(A) T2 (B) T1
(C) T3 (D) T4
10. The bit addressable RAM area in 8051 microcontroller is
(A) 00 H – 1 F H (B) 20 H – 2 F H
(C) 30 H – 3 F H (D) 40 H – 4 F H
11. What is the storage space required for a character ?
(A) 1 byte (B) 2 bytes
(C) 3 bytes (D) 4 bytes
12. Which is an infinite loop in C language ?
(A) for (x = 0 ; x 10, x + +) (B) for ( ; x 10)
(C) for (x = 0 ; x 10) (D) for ( ; ; x + +)

13. The direction of propagation of EM wave is obtained from
(A)
–E

–H
(
B)
–E
(C)
–E

–H
(D)
–H
14. The length of an antenna operating at frequency 0.5 GHz is
(A) 570 m (B) 5.70 m
(C) 57.0 m (D) 600 m
15. A pre-emphasis circuit provides extra noise immunity by
(A) boosting the bass frequencies.
(B) amplifying the higher audio frequencies.
(C) pre-amplifying the whole audio band.
(D) converting the phase modulation to FM.
16. In order to separate channels in a TDM receiver, it is necessary to use
(A) AND gates (B) band pass filters
(C) differentiators (D) integrators
17. The capacitive current flowing through the junction of a thyristor is given by

18. A dual converter is used in where
(A) Reversible d.c. is required.
(B) a.c. of higher frequency is required.
(C) a.c. of low frequency is required.
(D) ripple free d.c. is required.

19. Which is the static specification of a transducer ?
(A) Rise time
(B) Settling time
(C) Hysteresis
(D) Frequency response
20. In which mode the controller works as a variable gain amplifier ?
(A) On-off
(B) Proportional
(C) Integral
(D) PID
Question 21 to 30 :
The following items consist of two statements, one labelled as “Assertion (A)” and
the other labelled as “Reason (R)”. You are to examine these two statements carefully
and decide if the Assertion (A) and the Reason (R) are individually true and if so,
whether the reason is a correct explanation of the Assertion, select your answers to
these items using the codes given below and mark your answer accordingly.
Codes :
(A) Both (A) and (R) are true and (R) is the correct explanation of (A).
(B) Both (A) and (R) are true but (R) is not correct explanation of (A).
(C) (A) is true but (R) is false.
(D) (A) is false but (R) is true.
21. Assertion (A) : The temperature compensation circuits require additional hardware
and add to the complexity, instead one zener diode sufficies the
work.
Reason (R) : The temperature coefficient of 5 V zener diode is nearly zero.

22. Assertion (A) : The z-transforms study yields information on placement of poles
and zeroes in s-plane.
Reason (R) : Poles on the real axis in left half of s-plane give exponentially
decaying response.
23. Assertion (A) : Current 4-20 mA loop overcomes the problem of loop resistance
leading to signal degradation.
Reason (R) : V to F convertor is preferred because it is not affected by loop
resistance.
24. Assertion (A) : NAND gate provides universality.
Reason (R) : The universality is possible by De-Morgan’s theorem.
25. Assertion (A) : Queue system is not provided in 8086 microprocessor.
Reason (R) : Queue helps interfacing slow memory without speed degradation.
26. Assertion (A) : The memory addresses are manipulated in ‘c’ through pointers.
Reason (R) : Pointers in ‘c’ can be added.
27. Assertion (A) : Ionosphere is used for the transmission of HF waves.
Reason (R) : They are reflected back by the D, E, F1 and F2 layers.
28. Assertion (A) : Choppers are used for the speed control of d.c. drives.
Reason (R) : Cycloconverters may not be used for the control of d.c. drives.
D-8809 7 Paper-II
29. Assertion (A) : Optical fiber provides the attenuation of the order of 0.2 dB/km.
Reason (R) : Rayleigh scattering increases with the increase in the operating
wavelength.
30. Assertion (A) : Telemetry is used for smart instrumentation in digital control
systems in modern industrial units.
Reason (R) : They are capable of measuring the parameters of a process at a
distance.
31. See the stages in IC Fabrication below
(i) Etching
(ii) Cleaning
(iii) Masking and exposure
(iv) Application of photo resist
Mention the correct sequence followed :
(A) (i) (ii) (iii) (iv)
(B) (ii) (iv) (iii) (i)
(C) (i) (iii) (iv) (ii)
(D) (iv) (iii) (ii) (i)
32. Consider the input impedance of the following :
(i) open loop Op Amp
(ii) BJT
(iii) MOSFET
(iv) JFET
Which is the way of showing the decrease in input impedance ?
(A) (iv) (i) (ii) (iii)
(B) (iii) (ii) (i) (iv)
(C) (i) (iii) (iv) (ii)
(D) (ii) (iv) (i) (iii)

33. Consider the following logic families :
(i) CMOS (ii) TTL
(iii) LS TTL (iv) ECL
Write the sequence of power consumption in increasing order.
(A) (iii) (i) (ii) (iv)
(B) (ii) (iv) (i) (iii)
(C) (iv) (iii) (ii) (i)
(D) (i) (iii) (ii) (iv)
34. Consider the quantum efficiency of the detector in optical communication.
(i) Photo diode (ii) Photo transistor
(iii) APD (iv) PIN diode
Write the quantum efficiency of the above devices in decreasing order.
(A) (iii) (iv) (ii) (i)
(B) (iv) (iii) (ii) (i)
(C) (ii) (i) (iii) (iv)
(D) (i) (ii) (iii) (iv)
35. Consider the following transducers.
(i) Thermistor (ii) Thermocouple
(iii) RTD (iv) IC sensor
Write the linearity order of the above in increasing order.
(A) (ii) (iii) (i) (iv)
(B) (i) (ii) (iii) (iv)
(C) (iv) (iii) (ii) (i)
(D) (iii) (ii) (i) (iv)

36. Match List-I with List-II, and select the correct answers using the codes given below
the lists :
List-I List-II
(a) SCR (i) Relaxation oscillator
(b) Zener diode (ii) Voltage variable resistor
(c) UJT (iii) Voltage regulator
(d) FET (iv) Controlled Rectifier
Codes :
(a) (b) (c) (d)
(A) (i) (ii) (iii) (iv)
(B) (ii) (i) (iii) (iv)
(C) (iii) (ii) (i) (iv)
(D) (iv) (iii) (i) (ii)
37. Match List-I with List-II and select the correct answers using the codes given below
the lists :
List-I List-II
(a) Bode plot (i) Current source
(b) Transient analysis (ii) Frequency domain
(c) Norton’s theorem (iii) Stability analysis
(d) Fourier’s Transform (iv) Laplace transform
Codes :
(a) (b) (c) (d)
(A) (iv) (iii) (ii) (i)
(B) (iii) (iv) (i) (ii)
(C) (ii) (iii) (i) (iv)
(D) (i) (iv) (ii) (iii)

38. Match List-I with List-II and select the correct answers using the codes given below
the lists :
List-I List-II
(a) IC-723 (i) Lock-range
(b) Oscillators (ii) 25 mA
(c) IC-741 (iii) Voltage regulator
(d) PLL (iv) Positive feedback
Codes :
(a) (b) (c) (d)
(A) (iii) (iv) (ii) (i)
(B) (ii) (iii) (iv) (i)
(C) (i) (ii) (iii) (iv)
(D) (iv) (ii) (iii) (i)
39. Match List-I with List-II and select the correct answers using the codes given below
the lists :
List-I List-II
(a) Flip flop (i) Digital Multimeters
(b) Counters (ii) Memory
(c) XOR-gates (iii) Data acquisition systems
(d) D to A convertor (iv) Parity checkers
Codes :
(a) (b) (c) (d)
(A) (iii) (ii) (i) (iv)
(B) (iv) (ii) (i) (iii)
(C) (ii) (i) (iv) (iii)
(D) (i) (ii) (iii) (iv)

40. Match List-I with List-II and select the correct answers using the codes given below
the lists :
List-I List-II
(a) 8085 (i) On chip timer
(b) 8086 (ii) Serial I/O pins
(c) 8255 (iii) Segmented memory
(d) 8051 (iv) Hand-shake mode
Codes :
(a) (b) (c) (d)
(A) (i) (ii) (iii) (iv)
(B) (iv) (iii) (ii) (i)
(C) (iii) (ii) (i) (iv)
(D) (ii) (iii) (iv) (i)
41. Match List-I with List-II and select the correct answers using the codes given below
the lists :
List-I List-II
(a) Character storage space (i) \r
(b) O/p Array of characters (ii) while (1)
(c) Infinite Loop (iii) 1-byte
(d) bring cursor to the
beginning of current line
(iv) % S
Codes :
(a) (b) (c) (d)
(A) (iii) (iv) (ii) (i)
(B) (i) (ii) (iii) (iv)
(C) (iv) (iii) (ii) (i)
(D) (ii) (iii) (i) (iv)

42. Match List-I with List-II and select the correct answers using the codes given below
the lists :
List-I List-II
(a) EDFA (i) Ability to collect the light
(b) LASER (ii) Optical Amplifiers
(c) Numerical Aperture (iii) Spontaneous Emission
(d) LED (iv) Stimulated Emission
Codes :
(a) (b) (c) (d)
(A) (iii) (ii) (i) (iv)
(B) (ii) (iv) (i) (iii)
(C) (iv) (ii) (i) (iii)
(D) (iii) (ii) (iv) (i)
43. Match List-I with List-II and select the correct answers using the codes given below
the lists :
List-I List-II
(a) FM (i) Microwave generator
(b) AM (ii) Ratio detector
(c) Quantization (iii) PCM
(d) Magnetron (iv) Envelope detector
Codes :
(a) (b) (c) (d)
(A) (i) (ii) (iii) (iv)
(B) (iv) (ii) (iii) (i)
(C) (i) (ii) (iv) (iii)
(D) (ii) (iv) (iii) (i)

44. Match List-I with List-II and select the correct answers using the codes given below
the lists :
List-I List-II
(a) RTD (i) Infinite Resolution
(b) Hall Effect (ii) Change of Resistance
(c) Instrumentation Amplifier (iii) Magneto resistance
(d) LVDT (iv) High end variable gain
Codes :
(a) (b) (c) (d)
(A) (i) (ii) (iii) (iv)
(B) (iv) (iii) (ii) (i)
(C) (ii) (iii) (iv) (i)
(D) (i) (iv) (iii) (ii)
45. Match List-I with List-II and select the correct answers using the codes given below
the lists :
List-I List-II
(a) On-off control (i) Stability
(b) Proportional control (ii) Dead zone
(c) PID (iii) Residual error
(d) Routh-Hurwitz (iv) Zero offset error
Codes :
(a) (b) (c) (d)
(A) (iv) (iii) (ii) (i)
(B) (iv) (ii) (iii) (i)
(C) (iii) (ii) (iv) (i)
(D) (ii) (iii) (iv) (i)

Read the passage below, answer the questions from 46 to 50, that follow based on your
understanding of the passage.
Frequency modulation (FM) and phase modulation (PM) are two forms of angle modulation
which is a form of continuous wave or analog modulation whose chief characteristics are as
follows :
(1) The amplitude of the modulated carrier is kept constant.
(2) The frequency of the modulated carrier is varied by the modulating voltage.
In frequency modulation the carrier’s frequency deviation is proportional to the
instantaneous amplitude of the modulating voltage. In phase modulation, the carrier’s phase
deviation is proportional to the instantaneous amplitude of the modulating voltage. It has
been mathematically shown that as the modulating frequency decreases and the modulating
voltage amplitude remains constant the modulation index increases. The modulation index
determines how many side bands have significant amplitude. The major advantages of angle
modulation over amplitude modulation are
(1) The transmitted amplitude is constant and thus the receiver can be fitted with an
efficient amplitude limiter ; this characteristics has the advantage of improving
immunity to noise and interference.
(2) Since there is no natural limit to the modulation index, it can be increased to provide
additional noise immunity.
The noise-signal distribution is rectangular in AM and PM, whereas triangle in FM. To
reduce the effect of noise wideband FM is used for broadcast transmissions for the sound
accompanying TV transmissions. Narrow band FM is used for communications in
competition with single side band having its main applications in various forms of mobile
communications.
The reactance modulator is a direct method of generating FM. The alternative means of
generating FM the Armstrong system is one of which PM is initially generated but the
modulating frequencies are correctly bass-boosted ; thus FM results in output. A very small
frequency deviations are possible in basic Armstrong system.
46. In the spectrum of frequency modulated wave
(A) the carrier frequency disappears when the modulation index is large.
(B) the amplitude of any sideband depends on the modulation index.
(C) the total number of sideband depends on the modulation index.
(D) the carrier frequency cannot disappear.

47. The difference between phase and frequency modulation
(A) is purely theoretical because they are the same in practice.
(B) is too great to make the two system compatible.
(C) lies in the different definitions of the modulation index.
(D) lies in the poorer audio response of phase modulation.
48. Indicate the false statement regarding the Armstrong modulation system.
(A) The system is basically phase modulation not FM.
(B) Automatic frequency control is not needed as a crystal oscillator is used.
(C) FM must be used.
(D) Equalization is unnecessary.
49. Since noise-phase modulates the FM wave as the noise sideband frequency
approaches the carrier frequency, the noise amplitude
(A) remains constant
(B) is decreased
(C) is increased
(D) is equalized
50. Indicate which one of the following is not an advantage of FM and Amplitude
Modulation ?
(A) Better noise immunity is provided
(B) Lower Bandwidth is required.
(C) The transmitted power is more useful.
(D) Less modulating power is required.

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Contact Details:
University Grants Commission New Delhi
Bahadur Shah Zafar Marg,
Balmiki Basti,
Vikram Nagar,
New Delhi,
Delhi 110002 ‎
093 33 778791
India

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