1. How do you convert a XOR gate into a buffer and a inverter (Use only one XOR gate for each)?

Answer

2. Implement an 2-input AND gate using a 2x1 mux.

Answer

3. What is a multiplexer?

Answer

4. What is a ring counter?

Answer

5. Compare and Contrast Synchronous and Asynchronous reset.

Answer

6. What is a Johnson counter?

Answer

7. An assembly line has 3 fail safe sensors and one emergency shutdown switch.The line should keep moving unless any of the following conditions arise:

(1) If the emergency switch is pressed

(2) If the senor1 and sensor2 are activated at the same time.

(3) If sensor 2 and sensor3 are activated at the same time.

(4) If all the sensors are activated at the same time

Suppose a combinational circuit for above case is to be implemented only with NAND Gates. How many minimum number of 2 input NAND gates are required?

Answer

8. In a 4-bit Johnson counter How many unused states are present?

Answer

9. Design a 3 input NAND gate using minimum number of 2 input NAND gates.

Answer

10. How can you convert a JK flip-flop to a D flip-flop?

Answer

11. What are the differences between a flip-flop and a latch?

Answer

12. What is the difference between Mealy and Moore FSM?

Answer

13. What are various types of state encoding techniques? Explain them.

Answer

14. Define Clock Skew , Negative Clock Skew, Positive Clock Skew.

Answer

15. Give the transistor level circuit of a CMOS NAND gate.

Answer

16. Design a 4-bit comparator circuit.

Answer

17. Design a Transmission Gate based XOR. Now, how do you convert it to XNOR (without inverting the output)?

Answer

18. Define Metastability.

Answer

19. Compare and contrast between 1's complement and 2's complement notation.

Answer

20. Give the transistor level circuit of CMOS, nMOS, pMOS, and TTL inverter gate.

Answer

21. What are set up time and hold time constraints?

Answer

22. Give a circuit to divide frequency of clock cycle by two.

Answer

23. Design a divide-by-3 sequential circuit with 50% duty circle.

Answer

24. Explain different types of adder circuits.

Answer

25. Give two ways of converting a two input NAND gate to an inverter.

Answer

26. Draw a Transmission Gate-based D-Latch.

Answer

27. Design a FSM which detects the sequence 10101 from a serial line without overlapping.

Answer

28. Design a FSM which detects the sequence 10101 from a serial line with overlapping.

Answer

29. Give the design of 8x1 multiplexer using 2x1 multiplexers.

Answer

30. Design a counter which counts from 1 to 10 ( Resets to 1, after 10 ).

Answer

31. Design 2 input AND, OR, and EXOR gates using 2 input NAND gate.

Answer

32. Design a circuit which doubles the frequency of a given input clock signal.

Answer

33. Implement a D-latch using 2x1 multiplexer(s).

Answer

34. Give the excitation table of a JK flip-flop.

Answer

35. Give the Binary, Hexadecimal, BCD, and Excess-3 code for decimal 14.

Answer

36. What is race condition?

Answer

37. Give 1's and 2's complement of 19.

Answer

38. Design a 3:6 decoder.

Answer

39. If A*B=C and C*A=B then, what is the Boolean operator * ?

Answer

40. Design a 3 bit Gray Counter.

Answer

41. Expand the following: PLA, PAL, CPLD, FPGA.

Answer

42. Implement the functions: X = A'BC + ABC + A'B'C' and Y = ABC + AB'C using a PLA.

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43. What are PLA and PAL? Give the differences between them.

Answer

44. What is LUT?

Answer

45. What is the significance of FPGAs in modern day electronics? (Applications of FPGA.)

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46. What are the differences between CPLD and FPGA.

Answer

47. Compare and contrast FPGA and ASIC digital designing.

Answer

48. Give True or False.

(a) CPLD consumes less power per gate when compared to FPGA.

(b) CPLD has more complexity than FPGA

(c) FPGA design is slower than corresponding ASIC design.

(d) FPGA can be used to verify the design before making a ASIC.

(e) PALs have programmable OR plane.

(f) FPGA designs are cheaper than corresponding ASIC, irrespective of design complexity.

Answer

49. Arrange the following in the increasing order of their complexity: FPGA,PLA,CPLD,PAL.

Answer

50. Give the FPGA digital design cycle.

Answer

51. What is DeMorgan's theorem?

Answer

52. F'(A, B, C, D) = C'D + ABC' + ABCD + D. Express F in Product of Sum form.

Answer

53. How many squares/cells will be present in the k-map of F(A, B, C)?

Answer

54. Simplify F(A, B, C, D) = S ( 0, 1, 4, 5, 7, 8, 9, 12, 13)

Answer

55. Simplify F(A, B, C) = S (0, 2, 4, 5, 6) into Product of Sums.

Answer

56. The simplified expression obtained by using k-map method is unique. True or False. Explain your answer.

Answer

57. Give the characteristic tables of RS, JK, D and T flip-flops.

Answer

58. Give excitation tables of RS, JK, D and T flip-flops.

Answer

59. Design a BCD counter with JK flip-flops

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60. Design a counter with the following binary sequence 0, 1, 9, 3, 2, 8, 4 and repeat. Use T flip-flops.

Answer

## 49 Comments:

Thank you so much... It helps to know very basic concepts...

very helpful blogg....

thanks a ton dude

why answer not appear in question number 28..?pls post the answer..

IT WAS A VERY HELPFUL!!!THANX A LOT.

thanks a ton..was very helpful

Answers can't be seen for these questions! Please fix:

16,23,24,26,27,28,34,36,40,59,60

Thanks

Fantastic work, so well organized,

Thanks!

Thanks for posting this! It's a very good review for ASIC design interviews. Keep it up!

fix your stuff. answers cannot be seen for some.

Hi

I read this post 2 times. It is very useful.

Pls try to keep posting.

Let me show other source that may be good for community.

Source: Free interview questions

Best regards

Jonathan

not so helpful...

thnks a lot

very good...

Thanks a lot for your contribution...!

Hi

Tks very much for post:

I like it and hope that you continue posting.

Let me show other source that may be good for community.

Source: Interview questions answers

Best rgs

David

You have done a great job.. Thank you

i got job.. !!!!!!!

Tej

Thank you! These questions have help me lot.

Thank you! These questions have help me lot.

thanks alot......its very helpful...

hi, i wants answer of 29th quetion

i wants answer of question no.29

good job.. thank you

thanks a lot. . These basics helped a lot

i am very glad to you , due to thi tutorials i breshed my digital knowladge

vishwa

nice it helps more..:)

Excellent pieces. Keep posting such kind of information on your blog. I really impressed by your blog.

Vee Eee Technologies

this blog is really awesome..thanyou so much

its very help full for job searching peoples. thanku so mutch

very helpful to me.thank u so much

Please ,

Any one help me to clear this concept ,Pls explain it with truth table……tell me the logic

IT IS HELPFULL TO LEARN SOMETHING ABOUT INTERVIEW QUESTION ON VLSI SUBJECTS.SO I WAS GIVING LOTS OF THANKS FOR YOUR WEBSITES

Ali,

Which specific question are you referring to ?

thanks!!!

thank u...it was vry helpfull

Hi! is 11 the answer for question 7.

Thanks a lot...very usefull

cn any1 pls answer of 7 th one?? please....

awesome work..

awesome work.....

awesome work....

ans for 3:6 decoder is,

give three input bits to input of decoder.

ground the 8th output pin. thus for combinations from 000 to 110 output is available.

thanks a lot..........it proved very useful to me

These are really really great! Thanks! so is this something that a person graduated from a 4-year uni in electrical engineering should know? or a masters degree? was there some one who was recently graduated and was able to answer all these questions and get the job? i just graduated and i feel i know NOTHING ;( i dont know what to do!

For 7, if we use A, B, C, and E to stand for the 3 sensors and emergency, the four conditions can be expressed as "F=E+AB+BC" (you can use k-map to verify)

can any body pls provide answer for 60th one

Hi,

This is very helpful, thank you..

Purushotham.

Thank u so much for providing the information...... It will help a lot ...

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