VLSI Design - Objective type question and answers

Objective type question and answers for VLSI Design, also supports Electronics Devices and Circuits to some extent.

VLSI Design (Objective Type) Download

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UNIT - 1

Multiple choice

1. The speed – power product of any MOS technology is measured in                       [   C     ]

   a)KJ                                      b) MW-sec                               c) PJ                            d) Joules

2. For depletion mode mosfet, threshold voltage                                                     [   D     ]

    a) 0.2 V _DD                           b) -0.2 V _DD                             c) 0.8 V _DD                   d) -0.8 V _DD

3. The technology which is characterized by high speed                                             [   D     ]

    a)CMOS                               b)  BICMOS                             c)  GaAs                      d)ECL

4. Latch up in cmos device can be avoided by                                                          [   B     ]

     A) Increasing temp             b) doping control          c) increasing the substrate resistance

     d)decreasing substrate doping level

5. Material used for metallization is                                                                             [   A    ]

     a)Aluminum                       b) copper                     c)silver                                     d)tungsten

6.  Material used for gate oxide in MOS technology.                                                   [   C     ]

     a) Si                                                b) Ge                           c) Sio₂                                      d) AlO2

7. Poly silicon is a _________ material                                                                       [   C     ]

     a) Crystalline                      b) Amorphous             c) Poly crystalline                   d) None

8. Silicide is combination of                                                                                        [   A     ]

     a) Metal –poly                   b) Metal-Silicon           c) Metal-Ge                  d) Metal-S_iO₂

9. In modern CMOS fabrication, the pattern on each layer is created by

     a) Ion implantation             b) Oxidation                c) Photo lithography   d) Encapsulation

10. The advantage of twin- tub process                                                                                   [  C      ]

    a) Low complexity               b) Low cost depletion  c) Latch up immunity d) high mask count

Fill in the blanks:

11. Expansion of CVD is chemical vapour deposition

12. Electron lithography is preferred in submicron device dimension

13. The kinetics of thermal oxidation is modeled deal and groover model.

14. The static power dissipation in CMOS technology is zero

15. In normal mode of operation in CMOS, substrate terminal of NMOS is connected to V_ss and substrate terminal of PMOS is connected to V_dd

16. CMOS technology is high delay than bipolar Technology            

17. The deficiency of mos technology is limited load driving capacity                   

18. Under DEPLETION mode NMOS is ­­­­­­­­­­­­ON state.                                         

19. NMOS FET’s are faster than PMOS FET’s                                                             

20. Power dissipation in NMOS technology is high compared to CMOS technology.   

UNIT - 2

Multiple choice

1. MOSFET operated in saturation when                                                                     [  C     ]

(a) V_ds = v_gs-v_t     (b) v_ds < v_gs-v_t           (c) V_ds > v_gs-v_t     (d) V_ds < vt

2. For faster NMOS  circuits, one would choose the following type of substrate         [  B      ]

 (a) 110 Oriented n - type substrate                        (c) 111 Oriented p - type substrate

 (b) 100 oriented p - type substrate                        (d) 111 oriented n- type substrate           

3. Pull up to pull down ratio for n MOS inverter driven by another n MOS inverter is            [  D      ]

(a) 4:4                                                  (b) 4:1                          (c) 1:4                                        (d) 8:1

4. The following device is less likely to suffer latch up                                                           [  C      ]

(a)n MOS                                 (b) CMOS                     (c) BICMOS                             (d) PMOS

5. In cmos inverter if βn=βp  & if Vtn =Vtp, then the logic levels are disposed about at a point   where                                                                                                                   [   C     ]

(a)V_IN = V_out = 0.1 V_IN     (b V_IN = 0.5 V_DD      (c) V_IN = V_out =0.5 V_DD      (d) V_IN = V_out = V_DD

6. The figure of merit of MOS transistor can be expressed as                                      [  C      ]

            a) g _m C_g              b)                        c)                        d)

7. Typical mobility of holes (Bulk) is                                      [  D      ]

            a) 650cm²/V.sec          b) 240 cm²/V.sec         c) 1250 cm²/V.sec       d) 480 cm²/V.sec

8. Pickup the ‘true’ statement with respect to Bi-CMOS Inverter                                 [  C       ]

            a) Low input impedance          b) High output impedance       c) high noise margin

            d) Low driving capability

9. To achieve best performance NMOS inverter transfer characteristics, Zpu/Zpd ratio should be

            a) Zero                         b) One             c) As low as possible   d) As high as possible [ C        ]

10. Number of transistors to implement three-input AND gate using pass transistor logic is

            a) 6                              b) 3                  c) 5                  d) 9                              [ B       ]

           

Fill in the blanks:

11. An inverter driven through one or more pass transistor should have Zpu/Zpd ratio of 8:1

12. The threshold voltage is increased due to body effect

13. More lightly doped substrate less will be the body effect

14. The drain- source current (I_DS) for NMOS under saturation can be expressed as

15. Transconductance of MOS transistor (g_m) is expressed as

     

16. For devices of similar dimension n-channel is faster than the p – channel           

17. A simple bicmos inverter has high input impedance and low output impedance

18. The power dissipation is low in CMOS technology.                                  

19. Bi-CMOS inverter has high driving capability than cmos technology .                             

20. For high performance CMOS inverter should be low.                                 

UNIT – 3

Multiple choices

1. The color encoding for polysilicon is                                                                      [  A      ]

            (a) Red              (b) Green                   (c) Blue                                      (d) Orange

2. The color encoding of ‘VIA’ in double metal CMOS p-well process                       [  B      ]

            (a) Red             b) Black                      c) Brown                      d) Yellow

3. Metal 1 to metal 1 spacing in layout design is                                                            [  C    ]

            (a) 4 λ                            (b) 2λ                           (c)3λ                          ( d) 1λ

4. The buried contact is made between                                                                                      [  B    ]

            (a) Poly to metal   (b) poly to diff    (c) poly to diff using metal  (d) Metal to metal

5.In NMOS layout design style, the colour of contact cut                                [  A      ]

            a) Black          b) Green                      c) Blue                         d) Red

6. What is color of metal 1 (CMOS encoding)                                                             [  B      ]

            a) Black           b) Blue                         c) Red                                      d) Yellow

7. The p-type transistors are placed above the                                                                         [  C      ]

            a) Poly silicon              b) diffusion                 c) Demarcation line    d) metal

8. The minimum gap between diffusion and diffusion is                                            [  A      ]

            a) 2 λ                           b) 5 λ               c) 7 λ               d) 10 λ

9. The size of a transistor is usually designed in terms of                                            [  D      ]

            a) Drain                       b) source          c) metal            d) channel length

10. According to 2µm CMOS technology, the minimum separation between contact cuts

            a) 2 µm                        b) 4 µm           c) 6 µm            d) 5 µm                        [  B      ]

Fill in the blanks

11. The layer preferred for global distribution of power buses is METAL 2

12. STICK DIAGRAM is used to convey layer information.

13. For cmos circuits stick encodings for demarcation line is BROWN in color.

14. The power and ground lines often called POWER RANGE

15. The minimum width of metal 1 layer is 3λ

16. A MOS TRANSISTOR is formed wherever polysilicon  crosses Diffusion                                

17. Metal 1 for LOCAL DISTRIBUTION and metal 2 for GLOBAL DISTRIBUTION of power lines in stick notation

18. The minimum polysilicon width is 2λ.

19. As fabrication technology improves, the heat sink size REDUCES.                    

20. In CMOS design style, Demarcation line is shown by DOTTED LINE   

UNIT – 4

Multiple choice

1. Power dissipation per unit area is scaled by                                                                         [  C      ]

 (a)                           (b)                               (c)                                                      (d)                

2. Typical value of Diffusion capacitor(C _area ) in 5 µm technology                           [    A ]

a) 1.0x10 ^{– 4} pF/µm²    b) 1.0X10 ^{– 2} pF/µm²⁼   c) 0.1x10 ^{– 4} pF/µm²     d) 0.1x10 ^{– 2} pF/µm²

3. The rise time of CMOS inverters is                                                                          [  C      ]

a)  =        (b)  =           (c)   =        d)  =          

4. The typical value of load capacitance is                                                                  [  D      ]

a) CL < 10 ⁴ cg   (b) CL  10 ⁴ cg   (c) CL = 10 ¹⁴ cg   (d) CL  10 ¹⁴ cg  

5. The characteristics of a metal layer are                                                                     [          A  ]

a) Low R; low C          b) low R; moderate C  c) Low R; moderate C  d) moderate R; high C 

6. The typical sheet resistance of polysilicon for 5µm is                                             [  D      ]

            a) 0-10 Ω                     b) 10-14 Ω                   c) 120 to 140Ω                      d) 15 to 100 Ω

7. The overall delay T_d for n sections is given by                                                        [  B      ]

            a) T_d= nrc ()              b) T_d= n² rc()                       c) T_d = n²r² c()           d) T_d= n r² c()

8. Deposition of the metal/silicon alloy prior to sintering may be done with                [  A      ]

            a) Sputtering               b) diffusion                 c) Implantation                        d) Metallization

9. What is the formula for Rise-time estimation                                                             [  A    ]

a)  T_r=    b) T_r =            c) T_r =   d) T_r =

10. The formula for fall-time estimation in CMOS inverter is                                       [  C     ]

a) T_f =     b) T_f =            c) T_f =     d)

Fill in the blanks

11. The propagation delay of n sections is given by  

12. The layer in which metal is deposited on poly silicon is called SILICIDE.

13. The sheet resistance of p–diff is 2 : 5 times that of n-diffusion.

14. The values for N-diffusion region are 0.4 times the P-diffusion regions.

15. Bi-CMOS technology is reasonably good for HIGH LOW DRIVING CAPABILITY

16. Power consumption in CMOS circuits depends on FREQUENCY at which they operate.     

17. METAL 1 layer  is suitable for routing V_dd or Vss.

18. The LARGE CAPACITIVE load can’t be driven by a single inverter.                  

19. In Bi-Polar transistor collector current depends EXPONENTIALY on V_be.

20. The Delay for Bi-CMOS inverter is REDUCED by a factor of h _{f e} compared with a CMOS Inverter.