Test answers for Digital Electronics Test 2015

2 Answered Test Questions:

1. 9's complement of 56 is _____.

Answers:

• 87

• 49

• 43

• 35

2. The outputs Q and ¯Q of a master-slave S-R F/F are connected to its S and R inputs respectively. Its output Q, when clock pulses are applied, will be__________.

Answers:

• permanently 0

• permanently 1

• fixed 0 and 1

• complementary with every clock pulse

67 NOT Answered Yet Test Questions:

(hold on, will be updated soon)

3. Triggering action can be obtained in a J-K F/F by __________ .

Answers:

• joining J and K points to ground

• joining J point to Q and K to ¯Q

• joining J and K points to positive supply

• adding EX-OR gates at the output

4. Shifting the contents of a shift register one place to the  left is equivalent to

Answers:

• dividing the content by 10

• dividing the content by 2

• multiplying the content by 2

• None of above

5. The write-cycle time of a memory is 200 nsec. The maximum rate at which data can be stored is________ .

Answers:

• 200 words/sec

• 5*103 words/sec

• 5*106 words/sec

• 5*107 words/sec

6. The most important advantage of CMOS is its _____.

Answers:

• noise immunity

• input impedance

• low power consumption

• output impedance

7. The number of 4-line-to-16-line decoders required to make an 8-line-to-250-line decoder is_____ .

Answers:

• 16

• 17

• 32

• 64

8. When a large number of analog-signals are to be converted to the digital form, the most suitable ADC is _________ converter.

Answers:

• a forward-counter type

• an up/down counter

• a simultaneous type ADC

• a successive approximation type

9. A twisted ring counter consisting of 6 F/F will have

Answers:

• 6 states

• 12 states

• 64 states

• 128 states

10. In BCD to 7 segment decoder/driver, the input is 1000. The segments which will be lit are _____.

Answers:

• none

• all segments

• 2 segments

• 4 segments

11. The race-around condition occurs in J-K F/F when____________ .

Answers:

• both the inputs are 0

• both the inputs are 1

• the inputs are complementary

• any of the above input combinations is present

12. A multiplexer having 32 data input lines needs _____ select lines.

Answers:

• 5

• 4

• 3

• 6

13. One OR gate can work as a _____ comparator.

Answers:

• two-bit

• three-bit

• one-bit

• four-bit

14. What would be the value of X if (110001)2= X10?

Answers:

• 72

• 50

• 49

• 12

15. A universal register _____.

Answers:

• accepts serial input

• accepts parallel input

• gives serial and parallel outputs

• is capable of all the above

16. If an ADC with 8-bit output gives full-scale deflection for 12v analog-signal, its resolution is _____.

Answers:

• 8/12 v

• 8*12 mv

• 8/256 v

• 12/256 v

17. The counting sequence of a uniform counter is 000,001,011,111,110,100.The counter is a _____.

Answers:

• ripple binary counter

• combination counter

• ring counter

• Johnson counter

18. A half adder consists of an _____ gate and a _____ gate.

Answers:

• OR, NOR

• OR, XOR

• AND, XOR

• NOT, XOR

19. In the BCD number system, subtraction is done by the______ method.

Answers:

• 10's complement

• 2's complement

• 1's complement

• 9's complement

20. The time taken by an ADC to perform a conversion is usually referred to as

Answers:

• speed

• propogation- delay

• response- time

21. For a flip-flop with provisions of preset and clear__________.

Answers:

• preset and clear operations are preferred simultaneously

• while preseting, clear is disabled

• while clearing, preset is disabled

• both b and c

22. In an XNOR gate, input A is high and B is low. The output will _____.

Answers:

• be low

• be high

• switch between low and high

• None of the above

23. The design of a sequential circuit requires the use of _____.

Answers:

• K-maps

• state table/state diagram

• Quine McCluskey method

• None of the above

24. If in a clocked R-S F/F, point R is joined to point S through an inverter, the circuit will become a___________ .

Answers:

• J-K F/F

• T F/F

• D F/F

• None of the above

25. Which family has the fastest speed?

Answers:

• TTL

• ECL

• CMOS

• DTL

26. A monostable circuit gives a pulse-width output having tp=0.3 Rx.Cx. The device employed is likely to be_____ .

Answers:

• 74121

• 74122

• 74221

• 555-timer

27. If in a clocked R-S Flip Flop, point R is joined to point S through an inverter, the circuit will become a___________ .

Answers:

• J-K Flip Flop

• T Flip Flop

• D Flip Flop

• None of the above

28. A 4-bit synchronous counter uses flip-flops with the propagation delay time of 25nsec each. The maximum possible time required for the change of state will be _____.

Answers:

• 100 nsec

• 25 nsec

• 50 nsec

• 75 nsec

29. Which of the following memories uses an index-hole to  provide timing signals?

Answers:

• A magnetic tape

• A charged coupled device

• A floppy disk

• None of the above

30. If inverters are added to the inputs of AND gate, the logic function is _____.

Answers:

• OR

• NOR

• AND

• EX-OR

31. In a microprocessor, the adder circuit is a part of

Answers:

• instruction register

• memory

• ROM

• ALU

32. A multiplexer tree is needed when the number of inputs is more than _____.

Answers:

• 12

• 16

• 32

• 64

33. A monostable circuit uses a timing register of 10k ohms and a capacitor of 0.1µF capacity respectively. Its pulse-width will be approximately_____ .

Answers:

• 0.7 ms

• 1 ms

• 0.7 sec

• 1 sec

34. Semi-conductor memories are widely used because of their__________ .

Answers:

• small size

• low cost.

• compatibility with microprocessors

• All of the above

35. A transparent latch consists of a__________  .

Answers:

• T-type F/F

• D-type F/F

• T or D type F/F

• T and d type F/F

36. One of the two states of a circuit is stable and the others are quasi-stable. The circuit  is a _____ circuit.

Answers:

• flip-flop

• one-shot

• bi-stable multivibrator(MVR)

• free-running MVR

37. A semi-conductor ROM is basically a ________.

Answers:

• combinational circuit

• sequential circuit

• set of flip-flops memory elements

• None of the above

38. The minimum number of resistors required in a 4-bit network of weighted resistor type DAC is ______.

Answers:

• 4

• 8

• 15

• 16

39. The address bus width of a memory of size (1024*8) bit is _____.

Answers:

• 8 bits

• 10 bits

• 12 bits

• 16 bits

40. Decimal counters using flip flops and feedback are more popular than a decimal counter of ring counter type because of _____.

Answers:

• simple decade circuitry required

• economy in the number of flip flops

• high speed of operation

• its availability in IC form

41. Two mod-3 counters are cascaded. The circuit will behave as a _____.

Answers:

• mod-3 counter

• mod-6 counter

• mod-9 counter

• None of the above

42. Hexadecimal equivalent of (268)10 is_______ .

Answers:

• (10 C)16

• (9 C)16

• (8 B)16

• (7 E)16

43. How many memory locations can 14 address bits access?

Answers:

• 64,382

• 16,384

• 1024

• 2,048

44. Race condition occurs in _____.

Answers:

• a combinational circuit

• all the digital circuits

• a synchronous circuit

• an asynchronous circuit

45. The addition of hexadecimal number DF16 + AC16

Answers:

• 11C16

• 18B16

• 15B16

• 19E16

46. Shift-registers most commonly use _____.

Answers:

• D F/F

• R-S F/F

• J-K F/F

• T F/F

47. A 1 us pulse can be converted into a 1 ms pulse by using a _____ multivibrator(MVR).

Answers:

• monostable

• Schmitt-trigger

• latch

• free-running MVR

48. For a 12-bit ADC, the range of input-voltage is (0 to +10v).The voltage corresponding to LSB is _____.

Answers:

• 0

• 0.0012 v

• 0.0024v

• 0.833v

49. Pocket calculators use the_________ system.

Answers:

• BCD

• Exess-3

• gray code

• binary

50. A memory device that contains a SRAM and EEPROM in the same chip is called _____.

Answers:

• EAPROM

• EEPROM

• NVRAM

• DRAM

51. A flip-flop may be built with

Answers:

• NAND gates

• AND gates

• OR gates

• Any one of the above

52. A triggerable one-shot monostable MVR _____.

Answers:

• can be triggered in the ON as well as quiescent state

• can be triggered only in the quiescent state

• can be triggered only in the ON state

• does not require any triggering

53. The boolean expression xy + xz +xyz ( xy + z ) is equal to _____.

Answers:

• 0

• x

• y

• 1

• x(y+z)

54. In a 4-bit weighted-register DAC, the resistor value corresponding to MSB is 2k ohm. The resistor value corresponding to LSB will be _____.

Answers:

• 1 k ohm

• 2 k ohm

• 4 k ohm

• 16 k ohm

55. In the floating point system, the exponent is written in __________ notation.

Answers:

• gray code

• hexadecimal

• octal

• excess-32

56. A PLA consists of

Answers:

• AND matrrix

• OR matrix

• invert/non-invert matrix

• All of these

57. In a shift register, complemented output point Ā of the last flip-flop is joined to point J of the first flip-flop while its point K is joined to point A of the last flip-flop. The circuit will work as _____.

Answers:

• a shift count

• a shift register

• a ring counter

• None of the above

58. A memory in which the contents get erased when power-failure occurs is called_______ .

Answers:

• RAM

• EAROM

• PROM

• ROM

59. While designing a counter circuit, the preferred type of flip-flop is _____.

Answers:

• D-type

• R-S F/F

• J-K F/F

• latch

60. A circuit has an output that is determined by the present input as well as the previous output states. The circuit is known as _____.

Answers:

• a mealy machine

• a moore machine

• a sequential circuit

• None of above

61. A J-K F/F may be obtained by adding__________ .

Answers:

• AND gates to a clocked R-S F/F

• OR gates to a D F/F

• NAND gates to a T F/F

• NAND gates to a R-S F/F

62. Adding inverters to the input of an OR gate produces the _____ logic function.

Answers:

• NOR

• AND

• NAND

• EX-OR

63. The most suitable gate for comparing two bits is the _____ gate.

Answers:

• AND

• EX-OR

• OR

• NAND

64. In an IC-555-timer, the load can be connected _____.

Answers:

• only between the output terminal and the ground (GND)

• only between the output terminal and the VCC

• between the VCC and the GND

• between either the output terminal and the GND or between the output terminal and the VCC

65. LSI and VLSI devices use the _____ technology.

Answers:

• TTL

• ECL

• MOS

• RCL

66. The boolean expression XY+X+XY is equal to _____.

Answers:

• 1

• 0

• x

• y

67. The comparison time of ADC-0800 is in the range of _____.

Answers:

• a few tens of msec

• a few tens of millions of msec

• a few milli-secs

• a few micro-secs

68. In sequential circuits, memory elements are _____.

Answers:

• astable

• monostable

• bistable

• tristate flip-flops

69. In a karnaugh map, a quad eliminates _____ variables.

Answers:

• 4

• 2

• 8

• 1