EC-405 Analog Circuits - Jun 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
   aDiscuss the advantages and disadvantages of negative feedback amplifier in detail?
   How to answer

   • Define negative feedback amplifier and feedback factor
   • List advantages: stability, bandwidth, distortion, noise, impedance control
   • List disadvantages: gain reduction, instability, complexity
   • Explain each point briefly
2. 7 Marks
   bExplain with the help of mathematical expressions, how the negative feedback in amplifiers increases amplifier bandwidth and reduces distortion in amplifiers.
   How to answer

   • Write gain with feedback $A_f = A/(1+A\beta)$
   • Derive bandwidth extension $BW_f = BW(1+A\beta)$ for low/high cut-off
   • Derive distortion reduction $D_f = D/(1+A\beta)$
   • Explain physical interpretation with expressions
3. 7 Marks
   aExplain the working principle of Wein bridge oscillator with neat circuit diagram.
   How to answer

   • Draw Wein bridge network with Op-Amp and RC arms
   • Explain Barkhausen condition and lead-lag network
   • Derive frequency $f_0 = 1/(2\pi RC)$ and gain requirement 3
   • Explain sustained oscillations working
4. 7 Marks
   bDescribe in detail about LC type oscillators along with generalized analysis?
   How to answer

   • Draw generalized LC oscillator with active device and Z1, Z2, Z3 tank
   • Derive Barkhausen condition for oscillation
   • Show Hartley/Colpitts as special cases from reactance condition
   • Give frequency of oscillation expression
5. 7 Marks
   aWhat do you mean by IC. What are the characteristics of ICs and give its advantages.
   How to answer

   • Define IC as integrated circuit on single chip
   • List characteristics: miniaturization, reliability, low cost
   • List advantages over discrete circuits
   • Give classification brief
6. 7 Marks
   bDiscuss about the following

   1. i)Basic building components of ICs.
   2. ii)Data sheets.
   How to answer

   • Explain basic building components: transistors, diodes, resistors, capacitors in IC form
   • Explain data sheets: parameters, ratings, pin details
   • Give examples of information from datasheet
   • Summarize importance
7. 7 Marks
   aExplain about the Single input Unbalanced output differential amplifier with neat sketch.
   How to answer

   • Draw single input unbalanced output differential amplifier with two transistors
   • Explain operation with one input driven, other grounded
   • Give voltage gain and waveforms
   • Mention applications
8. 7 Marks
   bExplain characteristics of standard regulator ICs such as linear regulator.
   How to answer

   • Define linear voltage regulator ICs e.g., 78XX series
   • List characteristics: line/load regulation, ripple rejection, protection
   • Explain fixed vs adjustable regulators
   • Give typical specifications
9. 7 Marks
   aCompare and contrast the characterization of an ideal Op-Amp and practical Op-Amp.
   How to answer

   • List ideal Op-Amp parameters: infinite gain, BW, input impedance
   • List practical values: finite gain, offset, slew rate, CMRR
   • Compare in tabular form parameter-wise
   • Conclude effects on design
10. 7 Marks
    bExplain the following in detail:

    1. i)CMRR
    2. ii)Slew rate
    3. iii)Off-set voltage.
    How to answer

    • Define CMRR as $A_d/A_c$ and its importance
    • Define slew rate as max $dV_o/dt$ and its effect
    • Define offset voltage and nulling
    • Give typical values and formulas
11. 7 Marks
    aWith neat sketch explain the operation of Op-Amp as Integrator and differentiator.
    How to answer

    • Draw Op-Amp integrator with R input, C feedback and differentiator with C input, R feedback
    • Derive $V_o = -1/RC \int V_i dt$ for integrator
    • Derive $V_o = -RC dV_i/dt$ for differentiator
    • Explain waveforms and applications
12. 7 Marks
    bDraw the first order low pass Butterworth filter and obtain its gain and frequency response.
    How to answer

    • Draw first order low pass Butterworth filter using Op-Amp with RC network
    • Derive gain $A_f = 1+R_f/R_1$ and cutoff $f_H = 1/(2\pi RC)$
    • Sketch frequency response magnitude vs frequency
    • Explain roll-off -20 dB/decade
13. 7 Marks
    aExplain the operations of Mono stable Multivibrator using 555 timers.
    How to answer

    • Draw 555 timer monostable circuit with R-C timing network
    • Explain trigger, threshold and discharge operation
    • Derive pulse width $W = 1.1 RC$
    • Show trigger/output/capacitor waveforms
14. 7 Marks
    bWhat is the sample and hold circuit? Draw and explain the working of sample and hold circuit with suitable sketch.
    How to answer

    • Define sample and hold circuit and its need in ADC
    • Draw circuit with analog switch, hold capacitor and buffer Op-Amp
    • Explain sample mode and hold mode operation
    • Show input/output waveforms
15. 14 Marks
    Write a short note on any two

    1. i)Log/Antilog amplifier
    2. ii)Schmitt Trigger
    3. iii)Crystal oscillator
    4. iv)AVC using Op-Amp.
    How to answer

    • Select any two topics from four options
    • Give circuit diagram, working principle and expression for each
    • Mention applications and advantages
    • Conclude with comparison