EC-405 Analog Circuits - Nov 2023 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
   aWhat are the advantages and disadvantages to introduce negative feedback in amplifiers? Explain.
   How to answer

   • Define negative feedback in amplifiers
   • List advantages e.g. stability, bandwidth, distortion reduction
   • List disadvantages e.g. gain reduction, instability risk
   • Explain effect on gain, bandwidth and distortion briefly
2. 7 Marks
   bExplain in detail about Concept of feedback and their types with suitable examples.
   How to answer

   • Define feedback concept and feedback loop
   • Classify feedback types e.g. positive/negative, voltage/current, series/shunt
   • Give suitable example for each type
   • Summarize application of each type
3. 7 Marks
   aDraw the basic circuit of RC - Phase Shift Oscillator and explain its operation. Also derive the expression for frequency of Oscillation.
   How to answer

   • Draw basic RC phase-shift oscillator circuit with amplifier and 3 RC sections
   • Explain Barkhausen condition and 180+180 degree phase shift operation
   • Derive loop gain and condition for oscillation
   • Obtain expression for frequency of oscillation $f = 1/(2\pi RC\sqrt{6})$
4. 7 Marks
   bDraw and explain the operation of Colpitt's oscillator.
   How to answer

   • Draw Colpitt's oscillator circuit with capacitive voltage divider tank
   • Identify transistor/amplifier, L and C1-C2 tank circuit
   • Explain feedback and condition for sustained oscillation
   • Give frequency expression $f = 1/(2\pi\sqrt{LC_{eq}})$
5. 7 Marks
   aExplain the Advantages of Integrated Circuits (IC's).
   How to answer

   • Define integrated circuits
   • List advantages: size, cost, reliability, power, performance
   • Explain each advantage briefly
   • Contrast with discrete circuits
6. 7 Marks
   bExplain in detail about basic building components of IC.
   How to answer

   • List basic building components: resistors, capacitors, diodes, transistors
   • Explain monolithic fabrication of each component
   • Describe isolation and interconnection
   • Summarize IC construction process
7. 7 Marks
   aExplain the operation of Fixed and Adjustable Voltage Regulators. Give the advantages of adjustable voltage regulator over fixed voltage regulator?
   How to answer

   • Explain fixed voltage regulator operation e.g. 78xx series
   • Explain adjustable regulator operation e.g. LM317 with variable output
   • Compare adjustability, flexibility and component count
   • List advantages of adjustable over fixed type
8. 7 Marks
   bExplain about the Dual input Unbalanced output differential amplifier.
   How to answer

   • Draw dual-input unbalanced-output differential amplifier
   • Define dual input and single-ended output mode
   • Explain differential and common-mode operation
   • Give voltage gain and CMRR expression
9. 7 Marks
   aExplain the following parameters of an op-amp: i) Input bias current ii) Input offset current iii) Input offset voltage
   How to answer

   • Define input bias current, offset current, offset voltage
   • Give typical ideal vs practical values
   • Explain effect on op-amp output error
   • Mention compensation/nulling methods
10. 7 Marks
    bWith neat sketch explain the operation of OP Amp as Integrator and differentiator.
    How to answer

    • Draw op-amp integrator with R input and C feedback
    • Derive $V_o = -1/RC \int V_i dt$ and explain integration
    • Draw op-amp differentiator with C input and R feedback
    • Derive $V_o = -RC dV_i/dt$ and explain differentiation with waveforms
11. 7 Marks
    aWith a neat diagram explain the operation of instrumentation amplifier using Op-Amp and derive the necessary expression.
    How to answer

    • Draw three op-amp instrumentation amplifier circuit
    • Explain buffer stage and differential stage operation
    • Derive gain expression $A_v = (1+2R/R_g)(R_f/R_1)$
    • Mention high input impedance and CMRR advantages
12. 7 Marks
    bExplain characteristics of standard regulator ICs such as linear regulator.
    How to answer

    • Define linear/standard regulator ICs
    • List characteristics: dropout, regulation, ripple rejection, protection
    • Explain load and line regulation
    • Give examples e.g. 78xx series
13. 7 Marks
    aDraw the circuit of Schmitt trigger using 555 timer and explain its operation.
    How to answer

    • Draw 555 timer connected as Schmitt trigger with threshold-trigger tied
    • Explain upper and lower threshold switching
    • Describe hysteresis operation and waveforms
    • Mention applications in wave shaping
14. 7 Marks
    bDraw the Astable multivibrator circuit diagram using 555 timer and explain its working.
    How to answer

    • Draw astable multivibrator using 555 with RA, RB, C network
    • Explain charging-discharging through RA+RB and RB
    • Derive frequency/duty cycle expressions and waveforms
    • Mention applications as clock/oscillator
15. 14 Marks
    Write a short note on any two: i) Clipper and clampers circuits ii) Zero Crossing Detector iii) CMRR iv) Wien Bridge Oscillator
    How to answer

    • Select any two topics from i)-iv)
    • Give circuit/diagram, principle and working for each
    • Include relevant expressions/waveforms
    • Mention applications