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7/21/13 Only-VLSI: Interview Questions
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Only-VLSI
Welcome to Only-VLSI
Contents
Cracking Interview
Interview Questions
Digital Design Tutorial
Verilog Tutorial
Miscellaneous Concepts
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VLSI Interview Questions with Answers - 1
1. Why does the present VLSI circuits use MOSFETs instead of BJTs?
Answer
2. What are the various regions of operation of MOSFET? How are those
regions used?
Answer
3. What is threshold voltage?
Answer
4. What does it mean "the channel is pinched off"?
Answer
5. Explain the three regions of operation of a MOSFET.
Answer
6. What is channel-length modulation?
Answer
7. Explain depletion region.
Answer
8. What is body effect?
Answer
9. Give various factors on which threshold voltage depends.
Answer
10. Give the Cross-sectional diagram of the CMOS.
Answer
6 Comments
Labels: Interview Questions
Digital Design Interview Questions - All in 1
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
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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
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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.
Answer
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.)
Answer
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.
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(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
Answer
60. Design a counter with the following binary sequence 0, 1, 9, 3, 2, 8, 4
and repeat. Use T flip-flops.
Answer
44 Comments
Labels: Interview Questions
Digital Design Interview Questions - 6
1. What is DeMorgan's theorem?
Answer
2. F'(A, B, C, D) = C'D + ABC' + ABCD + D. Express F in Product of Sum form.
Answer
3. How many squares/cells will be present in the k-map of F(A, B, C)?
Answer
4. Simplify F(A, B, C, D) = ( 0, 1, 4, 5, 7, 8, 9, 12, 13)
Answer
5. Simplify F(A, B, C) = (0, 2, 4, 5, 6) into Product of Sums.
Answer
6. The simplified expression obtained by using k-map method is unique.
True or False. Explain your answer.
Answer
7. Give the characteristic tables of RS, JK, D and T flip-flops.
Answer
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8. Give excitation tables of RS, JK, D and T flip-flops.
Answer
9. Design a BCD counter with JK flip-flops
Answer
10. Design a counter with the following binary sequence 0, 1, 9, 3, 2, 8, 4
and repeat. Use T flip-flops.
Answer
1 Comments
Labels: Interview Questions
Microprocessor Interview Questions - 5
1. Why are program counter and stack pointer 16-bit registers?
Answer
2. What happens during DMA transfer?
Answer
3. Define ISR.
Answer
4. Define PSW.
Answer
5. What are the execution modes available in x86 processors?
Answer
6. What is meant real mode?
Answer
7. What is protected mode?
Answer
8. What is virtual 8086 mode?
Answer
9. What is unreal mode?
Answer
10. What is the difference between ISR and a function call?
Answer
1 Comments
Labels: Interview Questions
VLSI Interview Questions - 6
1. Why is NAND gate preferred over NOR gate for fabrication?
Answer
2. Which transistor has higher gain: BJT or MOSFET and why?
Answer
3. Why PMOS and NMOS are sized equally in a transmission gates?
Answer
4. What is SCR?
Answer
5. In CMOS digital design, why is the size of PMOS is generally higher than
that of the NMOS?
Answer
6. What is slack?
Answer
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7. What is latch up?
Answer
8. Why is the size of inverters in buffer design gradually increased? Why not
give the output of a circuit to one large inverter?
Answer
9. What is Charge Sharing? Explain the Charge Sharing problem while
sampling data from a Bus?
Answer
10. What happens to delay if load capacitance is increased?
Answer
3 Comments
Labels: Interview Questions
Microprocessor Interview Questions - 4
1. What is the size of flag register of 8086 processor?
Answer
2. How many pin IC 8086 is?
Answer
3. What is the Maximum clock frequency of 8086?
Answer
4. What is meant by instruction cycle?
Answer
5. What is Von Neumann architecture?
Answer
6. What is the main difference between 8086 and 8085?
Answer
7. What does EAX mean?
Answer
8. What type of instructions are available in instruction set of 8086?
Answer
9. How is Stack Pointer affected when a PUSH and POP operations are
performed?
Answer
10. What are SIM and RIM instructions?
Answer
1 Comments
Labels: Interview Questions
Microprocessor Interview Questions - 3
1. How many bits processor is 8086?
Answer
2. What are the sizes of data bus and address bus in 8086?
Answer
3. What is the maximum addressable memory of 8086?
Answer
4. How are 32-bit addresses stored in 8086?
Answer
5. What are the 16-bit registers that are available in 8086?
Answer
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6. What are the different types of address modes available in 8086?
Answer
7. How many flags are available in flag register? What are they?
Answer
8. Explain the functioning of IP (instruction pointer).
Answer
9. What are the various types of interrupts present in 8086?
Answer
10. How many segments are present in 8086? What are they?
Answer
0 Comments
Labels: Interview Questions
Digital Design Interview Questions - 5
1. Expand the following: PLA, PAL, CPLD, FPGA.
Answer
2. Implement the functions: X = A'BC + ABC + A'B'C' and Y = ABC + AB'C using
a PLA.
Answer
3. What are PLA and PAL? Give the differences between them.
Answer
4. What is LUT?
Answer
5. What is the significance of FPGAs in modern day electronics?
(Applications of FPGA.)
Answer
6. What are the differences between CPLD and FPGA.
Answer
7. Compare and contrast FPGA and ASIC digital designing.
Answer
8. 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
9. Arrange the following in the increasing order of their complexity:
FPGA,PLA,CPLD,PAL.
Answer
10. Give the FPGA digital design cycle.
Answer
2 Comments
Labels: Interview Questions
Digital Design Interview Questions - 4
1. Design 2 input AND, OR, and EXOR gates using 2 input NAND gate.
Answer
2. Design a circuit which doubles the frequency of a given input clock signal.
Answer
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3. Implement a D-latch using 2x1 multiplexer(s).
Answer
4. Give the excitation table of a JK flip-flop.
Answer
5. Give the Binary, Hexadecimal, BCD, and Excess-3 code for decimal 14.
Answer
6. What is race condition?
Answer
7. Give 1's and 2's complement of 19.
Answer
8. Design a 3:6 decoder.
Answer
9. If A*B=C and C*A=B then, what is the Boolean operator * ?
Answer
10. Design a 3 bit Gray Counter.
Answer
4 Comments
Labels: Interview Questions
Verilog Interview Questions - 3
1. How are blocking and non-blocking statements executed?
Answer
2. How do you model a synchronous and asynchronous reset in Verilog?
Answer
3. What happens if there is connecting wires width mismatch?
Answer
4. What are different options that can be used with $display statement in
Verilog?
Answer
5. Give the precedence order of the operators in Verilog.
Answer
6. Should we include all the inputs of a combinational circuit in the
sensitivity list? Give reason.
Answer
7. Give 10 commonly used Verilog keywords.
Answer
8. Is it possible to optimize a Verilog code such that we can achieve low
power design?
Answer
9. How does the following code work?
wire [3:0] a;
always @(*)
begin
case (1'b1)
a[0]: $display("Its a[0]");
a[1]: $display("Its a[1]");
a[2]: $display("Its a[2]");
a[3]: $display("Its a[3]");
default: $display("Its default")
endcase
end
Answer
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10. Which is updated first: signal or variable?
Answer
7 Comments
Labels: Interview Questions
VLSI Interview Questions - 5
This sections contains interview questions related to LOW POWER VLSI
DESIGN.
1. What are the important aspects of VLSI optimization?
Answer
2. What are the sources of power dissipation?
Answer
3. What is the need for power reduction?
Answer
4. Give some low power design techniques.
Answer
5. Give a disadvantage of voltage scaling technique for power reduction.
Answer
6. Give an expression for switching power dissipation.
Answer
7. Will glitches in a logic circuit cause power wastage?
Answer
8. What is the major source of power wastage in SRAM?
Answer
9. What is the major problem associated with caches w.r.t low power
design? Give techniques to overcome it.
Answer
10. Does software play any role in low power design?
Answer
1 Comments
Labels: Interview Questions
Digital Design Interview Questions - 1
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:
-
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(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
13 Comments
Labels: Interview Questions
VLSI Interview Questions - 4
1. Why is the number of gate inputs to CMOS gates (e.g. NAND or NOR
gates)usually limited to four?
Answer
2. What are static and dynamic power dissipation w.r.t to CMOS gate?
Answer
3. Draw Vds-Ids curve for a MOSFET. Now, show how this curve changes (a)
with increasing Vgs (b) considering Channel Length Modulation.
Answer
4. Which is fastest among the following technologies: CMOS, BiCMOS, TTL,
ECL?
Answer
5. What is a transmission gate, and what is its typical use in VLSI?
Answer
6. Draw the cross section of nMOS or pMOS.
Answer
7. What should be done to the size of a pMOS transistor inorder to increase
its threshold voltage?
Answer
8. Explain the various MOSFET Capacitances and their significance.
Answer
9. On what factors does the resistance of metal depend on?
Answer
10. Draw the layout a CMOS NAND gate.
Answer
1 Comments
Labels: Interview Questions
VLSI Interview Questions - 3
1. Explain the voltage transfer characteristics of a CMOS Inverter.
Answer
2. What should be done to the size of a nMOS transistor in order to increase
its threshold voltage?
Answer
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3. What are the advantages of CMOS technology?
Answer
4. Give the expression for CMOS switching power dissipation.
Answer
5. Why is static power dissipation very low in CMOS technology when
compared to others?
Answer
6. What is velocity saturation? What are its effects?
Answer
7. Why are pMOS transistor networks generally used to produce high signals,
while nMOS networks are used to product low signals?
Answer
8. Expand: DTL, RTL, ECL, TTL, CMOS, BiCMOS.
Answer
9. On IC schematics, transistors are usually labeled with two, or sometimes
one number(s). What do each of those numbers mean?
Answer
10. How do you calculate the delay in a CMOS circuit?
Answer
2 Comments
Labels: Interview Questions
VLSI Interview Questions - 2
1. Explain the various MOSFET capacitance and give their significance.
Answer
2. What is the fundamental difference between a MOSFET and BJT ?
Answer
3. What is meant by scaling in VLSI design? Describe various effects of
scaling.
Answer
4. What is early effect?
Answer
5. Compare and contrast analog and digital design.
Answer
6. What are various types of the number notations? Explain them.
Answer
7. Why are most interrupts active low?
Answer
8. Which is better: synchronous reset or asynchronous reset signal?
Answer
9. What is meant by 90nm technology?
Answer
10. Compare enhancement and depletion mode devices.
Answer
0 Comments
Labels: Interview Questions
Digital Design Interview Questions - 2
1. What are the differences between a flip-flop and a latch?
Answer
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2. What is the difference between Mealy and Moore FSM?
Answer
3. What are various types of state encoding techniques? Explain them.
Answer
4. Define Clock Skew , Negative Clock Skew, Positive Clock Skew.
Answer
5. Give the transistor level circuit of a CMOS NAND gate.
Answer
6. Design a 4-bit comparator circuit.
Answer
7. Design a Transmission Gate based XOR. Now, how do you convert it to
XNOR (without inverting the output)?
Answer
8. Define Metastability.
Answer
9. Compare and contrast between 1's complement and 2's complement
notation.
Answer
10. Give the transistor level circuit of CMOS, nMOS, pMOS, and TTL inverter
gate.
Answer
1 Comments
Labels: Interview Questions
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