Online Electronics and Communication Engineering Test - Digital Electronics Test 1



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Instruction:

  • This is a FREE online test. DO NOT pay money to anyone to attend this test.
  • Total number of questions : 20.
  • Time alloted : 30 minutes.
  • Each question carry 1 mark, no negative marks.
  • DO NOT refresh the page.
  • All the best :-).


1.

A decade counter skips

A.
binary states 1000 to 1111
B.
binary states 0000 to 0011
C.
binary states 1010 to 1111
D.
binary states 1111 to higher

Your Answer: Option (Not Answered)

Correct Answer: Option C

Explanation:

A decade counter counts from 0 to 9. It has 4 flip-flops. The states skipped are 10 to 15 or 1010 to 1111.

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2.

A ring counter with 5 flip flops will have

A.
5 states
B.
10 states
C.
32 states
D.
infinite states

Your Answer: Option (Not Answered)

Correct Answer: Option A

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3.

The minimum number of NAND gates required to implement the Boolean function A +AB + ABC is equal to

A.
0
B.
1
C.
4
D.
7

Your Answer: Option (Not Answered)

Correct Answer: Option A

Explanation:

A + AB +A B C = A + AB ( 1 + C) = A + AB = A(1 + B) = A.

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4.

The number of counter states which an 8 bit stair step A/D converter has to pass through before conversion takes place is equal to

A.
1
B.
8
C.
255
D.
256

Your Answer: Option (Not Answered)

Correct Answer: Option D

Explanation:

28 = 256.

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5.

A dynamic RAM cell which holds 5 V has to be refreshed every 20 ms so that the stored voltage does not fall by more than 0.5 V. If the cell has a constant discharge current of 0.1 pA, the storage capacitance of cell is

A.
4 x 10-6 F
B.
4 x 10-9 F
C.
4 x 10-12 F
D.
4 x 10-15 F

Your Answer: Option (Not Answered)

Correct Answer: Option D

Explanation:

Q = 20 x 10-3 x 0.1 x 10-12 = 2 x 10-15 C and .

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6.

The modulus of counter in the given figure is

A.
1
B.
2
C.
3
D.
4

Your Answer: Option (Not Answered)

Correct Answer: Option C

Explanation:

Third clock pulse resets the counter to 00 state. Hence mod is 3.

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7.

Which of the following is not a characteristic of a flip flop?

A.
It is a bistable device
B.
It has two outputs
C.
It has two outputs are complement of each other
D.
It has one input terminal

Your Answer: Option (Not Answered)

Correct Answer: Option D

Explanation:

Flip-flop has more than 1 input.

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8.

Y = A + A B is the same as

A.
Y = AB
B.
Y = A + B
C.
Y = A + B
D.
Y = A + B

Your Answer: Option (Not Answered)

Correct Answer: Option B

Explanation:

Verify by preparing truth table.

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9.

A microprocessor with a 16 bit address bus is used in a linear memory selection configuration. Address bus lines are directly uses as chip selects of memory chips with 4 memory chips the maximum addressable memory space is

A.
64 k
B.
16 k
C.
8 k
D.
4 k

Your Answer: Option (Not Answered)

Correct Answer: Option A

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10.

Assertion (A): A high density IC has more diodes, transistors and resistors per unit surface area.

Reason (R): A high density IC can handle high voltages.

A.
Both A and R are correct and R is correct explanation of A
B.
Both A and R are correct but R is not correct explanation of A
C.
A is true, R is false
D.
A is false, R is true

Your Answer: Option (Not Answered)

Correct Answer: Option C

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11.

The boolean expression for shaded area in the given figure is

A.
AB + AC
B.
ABC + ABC
C.
ABC + ABC
D.
None of these

Your Answer: Option (Not Answered)

Correct Answer: Option C

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12.

Which of the following is not a specification of D/A and A/D converters?

A.
Gain
B.
Drift
C.
Speed
D.
Accuracy

Your Answer: Option (Not Answered)

Correct Answer: Option A

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13.

Which of the following is susceptible to race condition?

A.
R-S latch
B.
D latch
C.
Both R - S and D latches
D.
None of the above

Your Answer: Option (Not Answered)

Correct Answer: Option A

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14.

For a NAND SR latch of input is the normal resting state of inputs is

A.
S = R = 1
B.
S = 0, R = 1
C.
S = 1, R = 0
D.
S = R = 0

Your Answer: Option (Not Answered)

Correct Answer: Option A

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15.

Assertion (A): The carry look ahead adder is very fast

Reason (R): The carry look ahead adder generates the carry and sum digits directly.

A.
Both A and R are correct and R is correct explanation of A
B.
Both A and R are correct but R is not correct explanation of A
C.
A is true, R is false
D.
A is false, R is true

Your Answer: Option (Not Answered)

Correct Answer: Option C

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16.

The high voltage level of a digital signal in positive logic is

A.
1
B.
0
C.
either 1 or 0
D.
-1

Your Answer: Option (Not Answered)

Correct Answer: Option A

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17.

In a sequential circuit the output at any instant depends on

A.
present inputs only
B.
past inputs only
C.
past outputs only
D.
past output and present input

Your Answer: Option (Not Answered)

Correct Answer: Option D

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18.

Which of the- following display consumes least amount of power?

A.
LCD
B.
LED
C.
Fluorescent display
D.
All display consume same power

Your Answer: Option (Not Answered)

Correct Answer: Option A

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19.

If one wants to design a binary counter, preferred type of flip-flop is

A.
D-type
B.
SR type
C.
Latch
D.
JK type

Your Answer: Option (Not Answered)

Correct Answer: Option A

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20.

Assertion (A): A presettable counter can be preset to any desired starting point

Reason (R): The maximum frequency of a ripple counter depends on the modulus.

A.
Both A and R are correct and R is correct explanation of A
B.
Both A and R are correct but R is not correct explanation of A
C.
A is true, R is false
D.
A is false, R is true

Your Answer: Option (Not Answered)

Correct Answer: Option B

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