[3] Digital Electronics

6. With four Boolean variables, how many Boolean expressions can be performed? A. 16 B. 256 C. 1024 (1 K) D. 64K (64 x 1024)

D

25. As the number of flip flops are increased, the total propagation delay of A. ripple counter increases but that of synchronous counter remains the same B. both ripple and synchronous counters increase C. both ripple and synchronous counters remain the same D. ripple counter remains the same but that of synchronous counter increases

A

43. Inverter 74 LS04 has following specifications I0H max = - 0.4 mA, I0L max = 8 mA, IIH max = 20 μA, IIL max = 0.1 mA The fan out of this inverter is A. 10 B. 20 C. 60 D. 100

B

45. The number FF in hexadecimal system is equivalent to number __________ in decimal system. A. 256 B. 255 C. 240 D. 239

B

8. To count 1000 bottles in a milk plant, the minimum number of flip flops requires is A. 12 B. 10 C. 8 D. 6

B

Hence as the number of flip-flops increases the delay increases. In synchronous counter clock pulses to all flip-flops are applied simultaneously. 26. In a 4 input OR gate, the total number of High outputs for the 16 input states are A. 16 B. 15 C. 14 D. 13

B

19. Assertion (A): ECL is fast as compared to TTL. Reason (R): ECL dissipates less power than TTL. 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

C

2. EPROM can be A. UVPROM B. EEPROM C. both UVPROM and EEPROM D. none of the above

C

1. A multilevel decoder is more costly as compared to single level decoder. A. True B. False

A

12. The K-map for a Boolean function is shown in figure. The number of essential prime implicants for this function is A. 4 B. 5 C. 6 D. 8

A

14. An AND gate has four inputs. One of the inputs is low and other inputs are high. The output A. is low B. is high C. is alternately low and high D. may be high or low depending on relative magnitudes of inputs

A

15. In the given figure, the flip flop is A. negative edge triggered B. positive edge triggered C. level triggered D. either (a) or (c)

A

18. If the I/P to the digital circuit is as follows in the figure, consisting of a cascade of 20 XOR gates is X, then the output Y is equal to A. 0 B. 1 C. X D. Y

A

21. What will be the maximum conversion time in 6 bit dual slope A/D converter uses a reference of -6v and a 1 MHz clock. It uses a fixed count of 40 (101000). A. 108 sec B. 63 μ sec C. 40 sec D. 80 μ sec

A

23. The input to a parity detector is 1001. The output is A. 0 B. 1 C. 0 or 1 D. indeterminate

A

31. For AB + A C + BC = AB + A C the dual form is A. (A + B) (A + C)(B + C) = (A + B)(A + C) B. (A + B ) (A + C)(B + C) = (A + B)(A + C) C. (A + B) (A + C) (B + C) = (A + B) (A + C) D. none of the above

A

33. Binary number 1101101101 is equal to decimal number A. 3289 B. 2289 C. 1289 D. 289

A

34. A 16:1 multiplexer has 4 select input lines. A. True B. False

A

36. What will be conversion time of a successive approximation A/D converter which uses 2 MHz clock and 5 bit binary ladder containing 8 V reference.? A. 2.5 μ sec B. 25 μ sec C. 3 μ sec D. 4 μ sec

A

4. The function of interface circuit is A. to match output conditions of driver with input conditions of load device B. to match output conditions of load device with input conditions of driver C. both (a) and (b) D. neither (a) nor (b)

A

47. Assertion (A): XOR gate is not universal gate. Reason (R): It is not possible to realize any Boolean function using XOR gates only. 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

A

= . 28. If A is 1011, A" is A. 1011 B. 0100 C. 1100 D. 1010

A

46. The inputs A, B, C of the given figure are applied to a 3 input NOT gate. The output is A. HIGH from 4 to 0 B. LOW from 0 to 4 C. HIGH from 1 to 0 and LOW from 0 to 4 D. LOW from 0 to 4 and HIGH from 2 to 4

C

48. The number of logic devices required in a Mod-16 synchronous counter are A. 4 B. 5 C. 6 D. 7

C

5. 127416 - 3A716 = __________ . A. ACA16 B. ACB16 C. ECD16 D. AAA16

C

50. The number of bits in EBCDIC is A. 12 B. 10 C. 8 D. 6

C

9. Decimal 8 in excess-3 code = A. 1000 B. 1001 C. 1011 D. 1111

C

Maximum conversion time = 63 + 40 = 103 μ sec and it takes 5 μ sec to transfer N2 to the O/P register. tcmax = 108 μ sec. 22. The modulus of counter in the given figure is A. 1 B. 2 C. 3 D. 4

C

44. A 4 bit ripple counter starts in 0000 state. When the counter reads 0010 the number of clock pulses which have occurred is A. 2 B. 18 C. 2 or 18 D. 2 or 18 or 34

D

49. A 2 bit BCD D/A converter is a weighted resistor type with ER = 1V, R = 1 MΩ and Rf = 10KΩ then Resolution in percent and volt is __________ . A. 1%, 1 mv B. 10%, 10 mv C. 10%, 1 mv D. 1%, 10 mv

D

7. A + (B . C) = A. A . B + C B. A . B + A . C C. A D. (A + B) . (A + C)

D

39. For the circuit of the given figure, the output equation is A. Y = ABCD B. Y = AB + CD C. Y = A + BCD D. Y = AB + CD

B

42. TTL is used in electronic calculators. A. True B. False

B

40. Using 2's complement, the largest positive and negative number which can be stored with 8 bits are A. +128 and -127 B. +128 and -128 C. +127 and -128 D. +127 and -127

C

0 + 0 = 0 0 + 1 = 1 + 0 = 1 1 + 1 = 10 i.e., 1 + 1 equals 0 with a carry of 1 to next higher column. 1 + 1 + 1 = 11 i.e., 1 + 1 + 1 equals 1 with a carry of 1 to next higher column. 11. BCD number 1100111 = __________ 10 A. 66 B. 67 C. 68 D. 69

B

10. The inputs to a 3 bit binary adder are 1112 and 1102. The output will be A. 101 B. 1101 C. 1111 D. 1110

B

13. When microprocessor processes both positive and negative numbers, the representation used is A. l's complement B. 2's complement C. signed binary D. any of the above

B

16. The number of switching functions of 3 variables are A. 3 B. 8 C. 16 D. 32

B

3. A full subtractor has a total of A. 2 inputs B. 3 inputs C. 4 inputs D. 5 inputs

B

32. A DAC has full scale output of 5 V. If accuracy is ± 0.2% the maximum error for an output of 1 V is A. 5 mV B. 10 mV C. 2 mV D. 20 mV

B

37. A 4 bit down counter can count from A. 0000 to 1111 B. 1111 to 0000 C. 000 to 111 D. 111 to 000

B

20. Assertion (A): Synchronous counter has higher speed of operation than ripple counter Reason (R): Synchronous counter uses high speed flip flops. 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

C

24. A 4 bit modulo 16 ripple counter uses JK flip-flops. If the propagation delay of each FF is 50 ns. The max. clock frequency that can be used is equal to A. 20 MHz B. 10 MHz C. 5 MHz D. 4 MHz

C

30. The number of flip flops needed for a Mod 7 counter are A. 7 B. 5 C. 3 D. 1

C

35. Which one of the following can be used as parallel to series converter? A. Decoder B. Digital counter C. Multiplexer D. Demultiplexer

C

17. The applications of shift registers are 1. Time delay 2. Ring counter 3. Serial to parallel data conversion 4. Serial to serial data conversion Which of the above are correct? A. 1, 2, 3 B. 2, 3, 4 C. 1, 2, 3, 4 D. 1, 2, 4

C

41. Three Mod-16 counters are connected in cascade. The maximum counting range is A. 16 B. 256 C. 4096 D. none of the above

C

38. Assertion (A): In computers the data is stored in hexadecimal form Reason (R): Hexadecimal representation is short as compared to binary representation. 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

D

27. For the ring oscillator shown in the figure, the propagation delay of each inverter is 100 pico sec. What is the fundamental frequency of the oscillator output __________ A. 10 MHz B. 100 MHz C. 1 GHz D. 2 GHz

D

29. 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

D