EC-701 VLSI Design - Dec 2024 Question Paper

Under each question, How to answer lists the points an answer should cover, outlined by CampusPrep from the syllabus. Check the details against your textbook.

1. 7 Marks
   aDiscuss the importance of packaging and testing in ensuring the reliability of integrated circuits.
   How to answer

   • Define IC packaging and testing stages
   • Role in reliability, protection, thermal and mechanical stress
   • Electrical performance, yield and fault coverage
   • Examples of package types and testing levels
2. 7 Marks
   bDefine :

   1. i)Oxidation
   2. ii)Lithography
   3. iii)Metallization
   How to answer

   • Define oxidation and its role in SiO2 growth
   • Define lithography and pattern transfer
   • Define metallization and interconnect formation
   • Relevance to VLSI fabrication sequence
3. 7 Marks
   aCalculate the total area occupied by an NMOS process compared to a CMOS process. How does the choice of technology (NMOS, CMOS, Bipolar, Hybrid) affect the design and performance of integrated circuits?
   How to answer

   • Area comparison NMOS vs CMOS layout rules
   • Transistor count, isolation and well overhead
   • NMOS, CMOS, Bipolar, Hybrid characteristics
   • Impact on density, power, speed and application choice
4. 7 Marks
   bAnalyze the significance of small signal models in predicting the behavior of MOSFETs at high frequencies. Provide examples of applications where these models are crucial.
   How to answer

   • Need for small-signal model at high frequency
   • Key elements: gm, gds, capacitances
   • Frequency response and fT prediction
   • Examples: RF amplifiers, oscillators, high-speed digital
5. 7 Marks
   aExplain short channel devices. Also mention its applications, advantages and limitations.
   How to answer

   • Define short-channel device and scaling
   • Applications in deep-submicron VLSI
   • Advantages: speed, density, low voltage
   • Limitations: SCE, DIBL, leakage, hot carrier
6. 7 Marks
   bHow diode and bipolar models are utilized in predicting the behavior of passive components in circuits? Explain.
   How to answer

   • Role of diode and BJT models in simulation
   • DC, AC and transient behavior prediction
   • Use for ESD, parasitics and passive modeling
   • Examples in SPICE circuit analysis
7. 7 Marks
   aExplain the simulation of a circuit using SPICE with suitable flowchart.
   How to answer

   • Steps of SPICE simulation: netlist to output
   • DC, AC, transient analyses
   • Flowchart of input, setup, solve, plot
   • Interpretation of simulation results
8. 7 Marks
   bDiscuss the impact of temperature dependence on the performance of BJTs in circuit simulations. How can temperature effects be mitigated in practical designs?
   How to answer

   • Temperature dependence of Is, beta, mobility
   • Effect on DC bias, gain and frequency response
   • Simulation models: TEMP, TNOM parameters
   • Mitigation: bias compensation, bandgap, layout
9. 7 Marks
   aExplain the operation of micro coded controllers in structured digital circuits.
   How to answer

   • Concept of microcoded control vs hardwired
   • Control store, sequencer operation
   • Use in structured digital datapath
   • Advantages for complex instruction control
10. 7 Marks
    bDesign a microprocessor using structured logic forms and discuss the advantages of this approach in terms of efficiency and scalability.
    How to answer

    • Structured logic forms: PLA, standard cell
    • Steps to design microprocessor blocks
    • Efficiency in area and design time
    • Scalability and modularity benefits
11. 7 Marks
    aCompare the storage capabilities of quasi-static and static register cells in digital circuits. How do these cells contribute to the overall functionality of register storage circuits? https://www.rgpvonline.com
    How to answer

    • Structure of quasi-static vs static register cells
    • Storage mechanism and clocking
    • Comparison of area, power, robustness
    • Role in register files and pipelines
12. 7 Marks
    bDesign a systolic array for parallel processing and discuss its advantages.
    How to answer

    • Concept of systolic array and data pumping
    • Design for parallel processing example
    • PE interconnection and timing
    • Advantages: throughput, regularity, scalability
13. 7 Marks
    aInvestigate the physical origin of latch-up in CMOS circuits and propose internal latch-up prevention techniques to mitigate this issue effectively.
    How to answer

    • Parasitic p-n-p-n thyristor in CMOS
    • Triggering by noise, ESD, supply spike
    • Prevention: guard rings, well contacts, spacing
    • Latch-up free design rules
14. 7 Marks
    bDesign a basic n-well CMOS process and discuss the enhancement techniques used in CMOS processing.
    How to answer

    • n-well CMOS process steps in sequence
    • Masking, oxidation, implantation, metallization
    • Enhancement: twin-tub, SOI, retrograde well
    • Cross-sectional diagram of process
15. 14 Marks
    Write short notes on (any two) :

    1. a)Algotronix
    2. b)Twin Tub Processes
    3. c)Interconnects in CMOS Processing Technology
    4. d)Level 1 Large signal model
    How to answer

    • Two topics selected with definition and key points
    • Relevant diagrams/process steps/models
    • Applications and significance in VLSI
    • Concise comparison or conclusion