1. A combinational logic circuit which sends data coming from a single source to two or more separate destinations is
Correct : D. demultiple xer
2. Data can be changed from special code to temporal code by using
Correct : A. shift registers
3. Odd parity of word can beconveniently tested by
Correct : D. xor gate
4. Which one of the following will give the sum of full adders as output ?
Correct : D. three bit counter
5. The number of full and half-adders required to add 16-bit numbers is
Correct : B. 1 half-adder,
15 full- adders
6. A one-to-four line demultiplexer is to be implemented using a memory. How many bits must each word have ?
Correct : A. 1 bit
7. What logic function is produced by adding an inverter to the output of an AND gate ?
Correct : A. nand
8. A demultiplexer is used to
Correct : A. route the data from single input to one of many outputs
9. How many full adders are required to construct an m-bit parallel adder ?
Correct : B. m-1
10. Parallel adders are
Correct : B. sequential logic circuits
11. The digital multiplexer is basically a combination logic circuit to perform the operation
Correct : C. and-or
12. How many lines the truth table for a four-input NOR gate would contain to cover all possible input combinations ?
Correct : D. 16
13. How many truth tables can be made from one function table ?
Correct : B. 2
14. A comparison between serial and parallel adder reveals that serial order
Correct : A. is slower
15. What is the largest number of data inputs which a data selector with two control inputs can have ?
Correct : B. 4
16. If a logic gates has four inputs, then total number of possible input combinations is
Correct : C. 16
17. If a logic gates has four inputs, then total number of possible input combinations is
Correct : A. input combination at the time
18. A combinational logic circuit which generates a particular binary word or number is
Correct : A. decoder
19. Which of the following circuit can be used as parallel to serial converter ?
Correct : A. multiplexer
20. In which of the following adder circuits, the carry look ripple delay is eliminated ?
Correct : C. parallel adder
21. Adders
Correct : D. all of these
22. Excess-3 code is known as
Correct : C. self- complementi ng code
23. The number of control lines for 32 to 1 multiplexer is
Correct : C. 5
24. The selector inputs to an arithmetic-logic unit (ALU) determine the:
Correct : B. arithmetic
25. What are the two types of basic adder circuits?
Correct : A. half adder and
26. The inverter OR-gate and AND gate are called deeision-making elements
because they can recognize some input while disregarding others. A gate
Correct : A. words,high
27. Which one of the following set of gates are best suited for 'parity' checking and 'parity' generation.
Correct : B. ex-nor or
ex-or gates
28. How many inputs are required for a 1-of-10 BCD decoder?
Correct : A. 4
29. Most demultiplexers facilitate which of the following?
Correct : B. single input, multiple outputs
30. One application of a digital multiplexer is to facilitate:
Correct : C. parallel-to- serial data conversion
31. Select one of the following statements that best describes the parity method of error detection:
Correct : A. best suited for detecting single-bit errors in transmitted codes.
32. A multiplexed display:
Correct : B. uses one display to present two or more pieces of information
33. In which of the following gates, the output is 1, if and only if at least one input is 1?
Correct : C. or
34. The time required for a gate or inverter to change its state is called
Correct : C. propagation time
35. The time required for a pulse to change from 10 to 90 percent of its maximum value is called
Correct : A. rise time iz
36. The maximum frequency at which digital data can be applied to gate is called
Correct : A. operating speed
37. What is the minimum number of two-input NAND gates used to perform the function of two input OR gate ?
Correct : C. three
38. The time required for a pulse to decrease from 90 to 10 per cent of its maximum value is called
Correct : B. decay time
39. Which of the following gates would output 1 when one input is 1 and other input is 0 ?
Correct : D. and gate
40. Which of the following expressions is not equivalent to X ' ?
Correct : D. x nor 1
41. Which of the following gates are added to the inputs of the OR gate to convert it to the NAND gate ?
Correct : A. not
42. The EXCLUSIVE NOR gate is equivalent to which gate followed by an inverter ?
Correct : D. xor
43. Which of the following gates is known as coincidence detector ?
Correct : A. and gate
44. Which table shows the logical state of a digital circuit output for every possible combination of logical states in the inputs ?
Correct : B. truth table
45. A positive AND gate is also a negative
Correct : D. or gate
46. An OR gate can be imagined as
Correct : B. switches connected in parallel
47. Which combination of gates does not allow the implementation of an arbitrary boolean function?
Correct : A. or gates and and gates only
48. The output of NOR gate is
Correct : C. high if all of its inputs are low
49. A toggle operation cannot be performed using a single
Correct : B. and gate
50. Which table shows the electrical state of a digital circuit's output for every possible combination of electrical states in the inputs ?
Correct : A. function table
51. What is the minimum number of 2 input NAND gates required to implement the function
F = (x'+y') (z+w)
Correct : C. 4
52. How many truth tables can be made from one function table ?
Correct : B. two
53. What is the largest number of data inputs which a data selector with two control inputs can have ?
Correct : B. 4
54. A combinational circuit is one in which the output depends on the
Correct : A. input combination at the time
55. The function of a multiplexer is
Correct : B. to select 1 out of n input data sources and to transmit it to single channel
56. For the device shown here, let all D inputs be LOW, both S inputs be HIGH, and the input be LOW. What is the status of the Y output?
Correct : A. low
57. Convert BCD 0001 0010 0110 to binary.
Correct : A. 1111110
58. Convert BCD 0001 0111 to binary.
Correct : C. 10010
59. How many 1-of-16 decoders are required for decoding a 7-bit binary number?
Correct : D. 8
60. The implementation of simplified sum-of-products expressions may be easily implemented into actual logic circuits using all universal gates with little or no increase in circuit complexity. (Select the response for the blank space that will BEST make the statement true.)
Correct : B. nand
61. Which of the following statements accurately represents the two BEST methods of logic circuit simplification?
Correct : A. boolean algebra and karnaugh mapping
62. Which of the following combinations cannot be combined into K-map groups?
Correct : C. diagonal corners
63. As a technician you are confronted with a TTL circuit board containing dozens of IC chips. You have taken several readings at numerous IC chips, but the readings are inconclusive because of their erratic nature. Of the possible faults listed, select the one that most probably is causing the problem.
Correct : C. an open input on the first ic chip on the board
64. Which gate is best used as a basic comparator?
Correct : C. exclusive-or
65. The device shown here is most likely a .
Correct : C. demultiplexe r
66. For the device shown here, assume the D input is LOW, both S inputs are HIGH, and the input is HIGH. What is the status of the outputs?
Correct : A. all are high.
67. In VHDL, macrofunctions is/are:
Correct : D. preprogra mmed ttl
devices.
68. Which of the following expressions is in the product-of-sums form?
Correct : A. (a + b )(c + d )
69. Which of the following is an important feature of the sum-of-products form of expressions?
Correct : A. all logic circuits are reduced to nothing more than simple and and or operations.
70. An output gate is connected to four input gates; the circuit does not function. Preliminary tests with the DMM indicate that the power is applied; scope tests show that the primary input gate has a pulsing signal, while the interconnecting node has no signal. The four load gates are all on different ICs. Which instrument will best help isolate the problem?
Correct : A. current tracer
71. The binary numbers A = 1100 and B = 1001 are applied to the inputs of a comparator. What are the output levels?
Correct : C. a > b = 1, a < b = 0, a = b = 0
72. A logic probe is placed on the output of a gate and the display indicator is dim. A pulser is used on each of the input terminals, but the output indication does not change. What is wrong?
Correct : A. the output of the gate appears to be open.
73. Each "1" entry in a K-map square represents:
Correct : A. a high for each input truth table condition that produces a high output.
74. Looping on a K-map always results in the elimination of:
Correct : C. variables within the loop that appear in both complemente d and uncompleme nted form.
75. What will a design engineer do after he/she is satisfied that the design will work?
Correct : B. program a chip and test it
76. What is the indication of a short on the input of a load gate?
Correct : D. there is a signal loss to all gates on the node, and the affected node will be stuck in the
low state.
77. In HDL, LITERALS is/are:
Correct : B. scalars.
78. Which of the following expressions is in the sum-of-products form?
Correct : D. ab + cd
79. The carry propagation can be expressed as .
Correct : B. cp = a + b
80. A decoder can be used as a demultiplexer by .
Correct : D. using the input lines for data selection and an enable line for data input
81. How many 4-bit parallel adders would be required to add two binary numbers each representing decimal numbers up through 30010?
Correct : C. 3
82. Which statement below best describes a Karnaugh map?
Correct : D. karnaugh maps provide a visual approach to simplifyin g boolean expression s.
83. A certain BCD-to-decimal decoder has active-HIGH inputs and active- LOW outputs. Which output goes LOW when the inputs are 1001?
Correct : C. 9
84. A full-adder has a Cin = 0. What are the sum and the carry (Cout) when A
= 1 and B = 1?
Correct : B. = 0, cout = 1
85. When adding an even parity bit to the code 110010, the result is .
Correct : A. 1110010
86. Which of the following combinations of logic gates can decode binary 1101?
Correct : D. one 4- input and gate, one inverter
87. What is the indication of a short to ground in the output of a driving gate?
Correct : B. there is a signal loss to all load gates.
88. How many outputs would two 8-line-to-3-line encoders, expanded to a 16-line-to-4-line encoder, have?
Correct : B. 4
89. A half-adder does not have .
Correct : A. carry in
90. A circuit that can convert one of ten numerical keys pressed on a keyboard to BCD is a .
Correct : A. priority encoder
91. The prefix on IC's indicates a broader operating temperature range, and the devices are generally used by the military.
Correct : A. 54
92. When an open occurs on the input of a TTL device, the output will .
Correct : B. react as if the open input were a high
93. The largest truth table that can be implemented directly with an 8-line- to-1-line MUX has .
Correct : C. 8 rows
94. Parity generation and checking is used to detect .
Correct : B. errors in binary data transmission
95. Except for , STD_LOGIC may have the following values.
Correct : C. \?\
96. A gate that could be used to compare two logic levels and provide a HIGH output if they are equal is a(n) .
Correct : B. xnor gate
97. VHDL is very strict in the way it allows us to assign and compare such as signals, variables, constants, and literals.
Correct : A. objects
98. The AND-OR-INVERT gates are designed to simplify implementation of
.
Correct : B. demorgan\s theorem
99. The output of a gate has an internal short; a current tracer will .