Paper 3 has been removed from NET from 2018 (Notification)- now paper 2 and 3 syllabus is included in paper 2. Practice both paper 2 and 3 from past papers.

# CBSE NET Electronic-Science June-2012 Solved Paper III

1. Consider an n-channel depletion mode MOSFET having following parameters: VTN = –2.5 V and Kn = 1.1 mA/V2 If VGS = 0V and VDS = 0.5 V, then current ID, is

1. 9.96 mA

2. 6.43 mA

3. 2.48 mA

4. 5.56 mA

2. The tie-set schedule gives relation between

1. branch currents and link currents

2. branch voltages and lnk currents

3. branch currents and link voltages

4. branch voltages and link voltages

3. The final value of 2S + 1/S4 + 8S3 + 16S2 + S is

1. 0

2. ¥

3. 1

4. 2

4. If differential amplifier has a differential gain of 20, 000. CMRR = 80 dB, then common mode gain is

1. 2

2. 1

3. ½

4. 0

5. For proper operation of integrators, its RC time constant and period T of the wave should be such that

1. T >> RC

2. T << RC

3. T = RC

4. T = 2 ln RC

6. The phase shift introduced by feed network or amplifier in Wein bridge oscillator is

1. 90°

2. 180°

3. 270°

7. For a certain logic family if VOL = 0.5 V, VIL = 1.2 V and VOH = 3.5 V, VIH = 2.8 V, then the noise margin is

1. 3 V

2. 1.7 V

3. 1.3 V

4. 0.7 V

8. Number of flip-flops needed to construct a shift register capable of storing decimal numbers upto 32 are

1. 6

2. 4

3. 5

4. 2

9. In the mode word format of 8251 during initialization, D6 and D7 bits as 0 and 1 signify

1. 16 X Baud Rate

2. Character length as 7 bits

3. Parity enable and even parity

4. No. Of stop bits as 1 (½)

10. The control word of ‘0B5H’ of 8253 indicates that the following counter is selected

1. Counter 0

2. Counter 1

3. Counter 2

4. Counter 3

11. In 8051, Pin 30 (ALE/PROG), if this bit is set as logic zero ( ‘0’ ), it signifies

1. Address is latched

2. For enabling internal ROM of programming

3. For disabling internal ROM programming

4. Both A and (C)

12. The expression a = 7/22 * (3.14 + 2) * ⅗ evaluates to

1. 8.28

2. 6.28

3. 3.14

4. 0

13. Which escape sequence takes the cursor to the beginning of the current line?

1. \n

2. \r

3. \a

4. \t

14. The depth of penetration of a wave in a lossy dielectric increases with increasing

1. Conductivity

2. Permeability

3. Wavelength

4. Permittivity

15. A very lossy, l/4 long, 50 ohm transmssion line is open circuited at the load end. The input impedance measured at the other end of the line is approximately

1. 0

2. 50 ohm

3. ¥

4. 200 ohm

16. In the spectrum of frequency modulated wave

1. The carrier frequency disappears when the modulation index is large.

2. The amplitude of any side band depends on the modulation index.

3. The total number of side bands depends on the modulation index.

4. The carrier frequency cannot disappear.

17. Indicate which one of the following is not an advantage of FM over AM:

1. Better noise immunity is provided

2. Lower bandwidth is required

3. The transmitted power is more useful

4. Less modulating power is required

18. Indicate the noise source which belongs to category a different from that of the other three.

1. Solar noise

2. Cosmic noise

3. Atmospheric noise

4. Galactic noise

19. Dispersion shifted wavelength in optical fiber is

1. 800 nm

2. 1300 nm

3. 1550 nm

4. 400 nm

20. The problem, with PI controller is its response to transients, is

1. very fast

2. having a dead zone

3. non-linear

4. sluggish

21. Which is the most linear temperature transducer?

1. Thermocouple

2. RTD

3. IC-sensor

4. Thermistor

22. The variations in the ambient temperature effect the following parameters:

1. Sensitivity

2. Accuracy

3. Stability

4. Above all

23. Consider the following statements regarding a semiconductor:

1. Acceptor level lies close to valence band.

2. Donor level lies close to valence band.

3. n-type semiconductor behaves as a conductor at 0° K.

4. p-type semiconductor behaves as an insulator at 0° K.

1. 1 and 2 are correct.

2. 1 and 3 are correct.

3. 2 and 3 are correct.

4. 1 and 4 are correct.

24. A network is said to be linear if and only if

1. Response is proportional to excitation function

2. Principle of superposition applies

3. Principle of homogeneity applies

4. It is reciprocal

1. Options 1 and 2 are correct.

2. Options 2 and 3 are correct.

3. Options 3 and 4 are correct.

4. Options 1 and 4 are correct.

25. Which of the following statements are correct?

1. A flip – flop is used to store 1-bit = of information

2. Race-around condition occurs in a J-K flip – flop when both inputs are I.

3. A transparent latch consists of a D-type flip – flop

1. 1 and 2 are correct.

2. 1 and 3 are correct.

3. 1, 2 and 3 are correct.

4. 1, 2 and 3 are not correct.

26. Which of the following statements will store value 3 in the variable a?

1. a = 15% 4

2. int a = (3 * 4)/(1 + 3)

3. int a = 3

4. int a = 6.0/2

1. Options 1, 2 and 3 are correct.

2. Options 2, 3 and 4 are correct.

3. Options 1 and 3 are correct.

4. Options 2 and 4 are correct.

27. In a rectangular metallic waveguide

1. Guided wavelength is never less than the free space wavelength

2. TEM mode is possible if the dimensions are properly chosen

3. vp × vg = C2

4. waves travel along all the four walls of the waveguide

1. Options 1 and 3 are correct.

2. Options 3 and 4 are correct.

3. Options 2 and 3 are correct.

4. Options 1 and 4 are correct.

28. Indicate the false statement in the case of Armstrong modulation system.

1. The system is basically phase and frequency modulation.

2. The system is also ampltude modulation.

3. Frequency multiplication must be used.

4. Equalization is unnecessary.

1. 1 and 2 are correct.

2. 1, 2 and 3 are correct.

3. 1 and 3 are correct.

4. 3 and 4 are correct.

29. DIAC is a

1. 2 terminal unidirectional switch

2. 2 terminal bi-directional switch

3. 3 layers and no gate device

4. 4 layers and no gate device

1. Options 2 and 3 are correct.

2. Options 2 and 4 are correct.

3. Options 1 and 3 are correct.

4. Options 1 and 4 are correct.

30. 1. a DVM, the accuracy of the measurement depends on I. No. Of A/D conversions in a second.

31. The resolution of A/D converter.

32. A statistical processing of samples and a huge memory.

33. Speed of the processor should be high.

1. 1, 2 and 3 are to be fulfilled

2. 2, 3 and 4 are to be fulfilled

3. 1, 3 and 4 are to be fulfilled

4. 1, 2 and 4 are to be fulfilled

• Assertion (A): A BJT is said to be operating in a saturation region if both the junctions are forward biased.
• Reason (R): In saturation region collector doping concentration is reduced.
1. Both A and R are true and R is the correct explanation of (A).

2. Both A and R are true, but R is not the correct explanation of (A).

3. A is true and R is false.

4. A is false and R is true.

• Assertion (A): Schmit trigger employs positive feedback and has hysteresis property that helps to compare two voltage levels.
• Reason (R): In some logic circuits rise and fall time play important role in switching. Schmit trigger improves the rise and fall time.
1. Both A and R are true and R is the correct explanation of (A).

2. Both A and R are true, but R is not the correct explanation of (A).

3. A is true and R is false.

4. A is false and R is true.

• Assertion (A): The fan out of a CMOS gate is poor.
• Reason (R): The current driving capability of CMOS is poor.
1. Both A and R are true and R is the correct explanation of (A).

2. Both A and R are true, but R is not the correct explanation of (A).

3. A is true and R is false.

4. A is false and R is true.

• Assertion (A): In 8085 processor, lower byte of address bus and data bus are multiplexed. A latch is required to separate address lines and data lines.
• Reason (R): Multiplexing makes processor slow speed and compact.
1. Both A and R are true and R is the correct explanation of (A).

2. Both A and R are true, but R is not the correct explanation of (A).

3. A is true and R is false.

4. A is false and R is true.

• Assertion (A): Relational operators cannot be used to evaluate whether a condition evaluates to true (T) or false (F).
• Reason (R): Use of ‘=’ as relational operator will form a syntax error.
1. Both A and R are true and R is the correct explanation of (A).

2. Both A and R are true, but R is not the correct explanation of (A).

3. A is true and R is false.

4. A is false and R is true.

• Assertion (A): Radio and Television receivers are generally of superheterodyne type.
• Reason (R): Wireless communication is possible by receiving signals through superheterodyne receivers.
1. Both A and R are true and R is the correct explanation of (A).

2. Both A and R are true, but R is not the correct explanation of (A).

3. A is true and R is false.

4. A is false and R is true.

• Assertion (A): The LED is a light emitting diode, that gives out spontaneous emissions, when it is energized.
• Reason (R): The recombination of holes and electrons in semiconductor materials gives off energy in terms of light and heat.
1. Both A and R are true and R is the correct explanation of (A).

2. Both A and R are true, but R is not the correct explanation of (A).

3. A is true and R is false.

4. A is false and R is true.

• Assertion (A): Power is integration of energy over a period of time.
• Reason (R): The accuracy of power measurement is dependent on integration time constant.
1. Both A and R are true and R is the correct explanation of (A).

2. Both A and R are true, but R is not the correct explanation of (A).

3. A is true and R is false.

4. A is false and R is true.

34. Arrange the following in the increasing order of their forbidden energy gap:

1. Conductors

2. Insulators

3. Germanium

4. Silicon

1. 1, 2, 3, 4

2. 1, 2, 4, 3

3. 1, 3, 4, 2

4. 1, 4, 3, II

35. The correct order in which time domain response is obtained for a network

1. Laplace transform

2. Differential equation

3. Time domain response

4. Network

1. 1, 2, 3, 4

2. 2, 3, 4, 1

3. 3, 4, 2, 1

4. 4, 2, 1, 3

36. The correct start to end sections of a regulator circuit are

1. Filtering

2. Protection

3. Rectification

4. Regulation

1. 2, 1, 3, 4

2. 3, 2, 4, 1

3. 1, 3, 4, 2

4. 4, 2, 1, 3

37. Arrange the following logic families in the decreasing order of their propagation delay:

1. CMOS

2. TTL

3. ECL

4. DTL

1. 2, 3, 4, 1

2. 4, 2, 3, 1

3. 3, 1, 2, 4

4. 1, 4, 2, 3

38. The interrupts in 8085 processor are

1. RST 6.5

2. RST 5.5

3. TRAP

4. RST 0

Keep the sequence from least priority to highest priority.

1. 3, 1, 2, 4

2. 4, 1, 2, 3

3. IV, II, 1, 3 D 3, 4, 2, 1

39. The correct sequence to write a loop statement is formed

1. body

2. main ()

3. test condition

4. initialization

1. 1, 4, 2, 3

2. 4, 3, 1, 2

3. 3, 2, 4, 1

4. 2, 4, 3, 1

40. The following frequency bands are used in microwaves:

1. Ku band

2. Ka band

3. L band

4. C band

The correct sequence in decreasing frequency is by:

1. 2, 3, 4, 1

2. 1, 2, 3, 4

3. 2, 1, 3, 4

4. 2, 1, 4, 3

41. Consider the following communication systems:

1. Microwave communication system

2. Optical communication system

3. AM Broadcast system

4. FM Broadcast system

The correct sequence of these systems from the point of view of increasing order of bandwidth is

1. 2, 1, 4, 3

2. 1, 2, 3, 4

3. 3, 4, 2, 1

4. 4, 3, 1, 2

42. The following are the fibers used in optical communication systems:

1. Plastic fibers

2. Plastic clad glass fibers

3. Glass fibers operating at 1330 nm

4. Glass fibers operating at 1550 nm

The correct sequence of attenuation of the above fibers in increasing order are:

1. 1, 2, 3, 4

2. 4, 3, 2, 1

3. 2, 1, 4, 3

4. 4, 2, 1, 3

43. Arrange the steps given below in correct order:

1. Network function

2. Change of sign

3. Stability

4. Routh array

The order in which the stability is evaluated using Routh criterion:

1. 1, 3, 2, 4

2. 1, 4, 2, 3

3. 4, 1, 3, 2

4. 3, 2, 1, 4

44. Match the given list of devices with their respective application:

 List-I List-II Diode Tunnel diode Zener diode PIN diode Rectification Microwave switching Oscillator Voltage regulator
• A
• B
• C
• D
• 1
• 3
• 4
• 2
• 1
• 4
• 3
• 2
• 1
• 2
• 3
• 4
• 1
• 4
• 2
• 3

45. Match List-I with List-II and select the correct answer using codes given below:

 List-I List-II Voltage source in a branch Hysteresis Non-bilateral Transistor small signal model Polar capacitor Super node h-parameters Avoid false triggering
• A
• B
• C
• D
• 1
• 4
• 3
• 2
• 3
• 1
• 2
• 4
• 2
• 4
• 1
• 3
• 4
• 2
• 3
• 1

46. Match List-I with List-II and select the correct answer using codes given below:

 List-I List-II Gating pulse Series pass element Lock range Base width modulation BJT Monostable multivibrator Voltage regulator PLL
• A
• B
• C
• D
• 1
• 2
• 4
• 2
• 2
• 3
• 4
• 1
• 3
• 4
• 1
• 2
• 4
• 2
• 3
• 1

47. Match the following list:

 List-I List-II Positive OR Positive AND Positive NOR Positive NAND Negative NAND Negative AND Negative OR Negative NOR
• A
• B
• C
• D
• 3
• 2
• 1
• 4
• 1
• 4
• 2
• 3
• 2
• 1
• 3
• 4
• 2
• 3
• 1
• 4

48. Match the following:

 List-I List-II MOV A, B JNC = address OR A, B ADD A, H Logical instruction Arithmetic instruction Data transfer Branching instruction
• A
• B
• C
• D
• 2
• 3
• 1
• 4
• 3
• 4
• 1
• 2
• 4
• 3
• 2
• 1
• 4
• 1
• 3
• 2

49. Match List-I with List-II and select the correct answer using codes given below:

 List-I List-II call by reference size of (float) & return (a, b) Incorrect statement Function 4 bitwise AND
• A
• B
• C
• D
• 1
• 2
• 3
• 4
• 4
• 3
• 2
• 1
• 2
• 3
• 4
• 1
• 3
• 4
• 1
• 2

50. Match List-I with List-II and select the correct answer using the codes given below:

 List-I List-II Ferrite devices Magnetron Klystron Gun-diode Oscillator Bunching Cross field devices Circulators
• A
• B
• C
• D
• 4
• 2
• 1
• 3
• 4
• 3
• 2
• 1
• 3
• 4
• 2
• 1
• 1
• 2
• 3
• 4

51. Match the following:

 List-I List-II Digital Filters Signal Processing Time Division Mulplexing Frequency Division Multiplexing More channels are = accommodated Slow speed of data transfer Hardware techniques Software Btechniques
• A
• B
• C
• D
• 4
• 3
• 2
• 1
• 1
• 2
• 3
• 4
• 3
• 4
• 1
• 2
• 4
• 3
• 1
• 2

52. Match List-I with List-II and select the correct answer using the codes given below:

 List-I List-II Fan regulator SCR Choppers Quantum efficiency Two transistor model dc-dc conversion Triac-Diac pair LED
• A
• B
• C
• D
• 2
• 3
• 4
• 1
• 4
• 3
• 1
• 2
• 3
• 1
• 2
• 4
• 3
• 2
• 1
• 4

53. Match the following:

 List-I List-II Small displacement Phase measurement Slowly varying signals Crystal structure DSO X-ray diffractometer CRO LVDT
• A
• B
• C
• D
• 4
• 3
• 1
• 2
• 3
• 2
• 4
• 1
• 2
• 1
• 3
• 4
• 1
• 4
• 2
• 3

## Read the Following Paragraph and Answer the Questions 71 to 75:

An operational amplifier is a direct coupled high gain amplifier with feedback. It is employed to perform a wide variety of functions such as summer, integrator, differentiator, logarithmic amplifier, oscillators, filters, comparators voltage to frequency converter, amplitude modulators, sample and hold circuit and so on:

An ideal Op-Amp has infinite input = resistance, zero output resistance, infinite voltage gain and bandwidth, zero offset and no drift. An ideal Op-Amp is a perfectly balanced circuit such that output voltage is zero for two equal input signals. However a real Op-Amp exhibits imbalance due to mismatch at the input differential stage. It gives rise to offsets. In practical applications offsets are removed using balancing networks. In general an Op-Amp consists of the following four stages:

1. Differential amplifier first stage

2. Differential amplifier second stage

3. Emitter follower

4. Level translator and output stage It is most widely used analog device.

5. Which is a non-linear application?

1. I-V converter

2. Sample-and-hold

3. Voltage follower

4. Active filter

6. Analog multiplication is carried out with

1. Scalar

2. Precision rectifier

3. Sample-and-hold circuit

4. Logarithmic amplifier

7. Very high input resistance differential stages are used in Op-Amp

1. To minimise input offset voltage

2. To minimise output offset voltage

3. To minimise input offset current

4. To minimise output offset current