Wednesday, July 23, 2008

VLSI INTERVIEW QUESTIONS(part 1)

The questions listed below are some of the questions that were asked in VLSI interviews

1. What is Bird's beak?

2. Is there any negative frequency? If so what are its implications?

3. Why GaAs is advantageous over Silicon?

4. In fabrication GaAs cannot be everywhere why?

5. Why Gold is used during fabrication?

6. Why is Silicon used more than GaAs? (Technical points only)

7. Silicon's advantages over GaAs

8. State Moore’s law.

9. Design the 4:1 multiplexer circuit using TG switches.

10. Design a 4:1 mux using three 2:1 TG multiplexers.

11. Consider the 2-input XOR function.
a) Design an XOR gate using a 4:1 mux.
b) Modify the circuit in a) to produce a 2-input XNOR

12. Design a CMOS logic gate for the function f= a.b+a.c+b.d

13. Design a NAND3 gate using an 8:1 mux

14. Design a NOR3 gate using an 8:1 mux as a basis.

15. A sample of silicon is doped with arsenic with Nd = 4 x 1017 cm3. Find the majority carrier density, minority carrier density and calculate the electron and hole mobilities and then find the conductivity of the sample.

16 A region of silicon is doped with both phosphorus and boron. The p-doping is Nd = 2 x 1016 cm-3 while the B-doping level is Na =6 x 1018 cm-3. Determine the polarity(n or p) of the region, and find the carrier densities.

17. Four nFETs are used as pass transistor . The input voltage is set to Vin=Vdd=5V and it is given that Vth= 0.75V. Suppose that the signals are initially at (1,1,0,0) and are then switched to (0,1,1,1). Find the value of Vout.

18. Design a driver chain that will drive a load capacitance of CL =40pF , if the initial stage has an input capacitance of Cin =50fF.Use ideal scaling to determine the number of stages and the relative sizes.

19. Explain the DCcharacteristics of CMOS inverter

20. What is switched capacitance?

21. How switched capacitances are useful in design?

22. Use only 2:1 Mux to create a Full adder

23. Why should the testing be done?

24. Write S&H Equation?

25.Difference between MOSFET, MISFET, MESFET?

26. Which terminal in a transistor has the largest area? why?

27. Draw a current mirror circuit?

28. Define Slew Rate and CMRR in an Opamp and its characteristics?

29. Different A2D converters and advantages over the other?

30. CMOS advantages and disadvantages

31. What is Verilog and how is it useful?

32. VLSI simulation is given importance why?

33. How many terminals are present in a MOSFET? and define their characteristics?

34. Frequency spectrum ranges?

35. What is STA(Static timing Analysis)?

36. Where is NMOS used and why?

37. Draw capacitance curve of MOSFET?

38. What acid is used to remove Silicon Nitride?

39. What acid is used to remove Silicon DiOxide?

40. What is Dry Etching(Plasma Etching)?

41. What is SOI and mention its advantages?

42. What is LOCOS how is it different from normal techniques?

43. Threshold voltage and Body effect are related how?

The questions are contributed by friends, colleagues and WWW. All contributions are appreciated.
To get the ANSWERS do mail me.

No comments: