EX-305 Analog Electronics - Dec 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 do you mean by breakdown? Why the operation of P-N junction in the breakdown region should be avoided?
   How to answer

   • Define breakdown in P-N junction - Zener and avalanche breakdown
   • Explain mechanism of breakdown with reverse bias
   • Explain why operation in breakdown region damages device due to excessive current/heating unless designed e.g. Zener
2. 7 Marks
   bExplain the working of half wave rectifier with the help of diagram.
   How to answer

   • Circuit diagram of half wave rectifier with transformer, diode, load
   • Working during positive half cycle - diode forward biased
   • Working during negative half cycle - diode reverse biased
   • Input-output waveforms
3. 7 Marks
   aDiscuss the principle working of Zener diode and tunnel diode.
   How to answer

   • Construction and doping of Zener diode and breakdown operation
   • Construction and heavy doping, tunneling principle of tunnel diode
   • V-I characteristics of both
   • Applications comparison
4. 7 Marks
   bShow that the maximum rectification efficiency of a full wave rectifier is $81.2\%$.
   How to answer

   • Define rectification efficiency as DC output power / AC input power
   • Derive $I_{dc}$, $I_{rms}$ for full wave rectifier
   • Show $\eta = 81.2\%$ for ideal case $R_f=0$
   • State maximum condition
5. 7 Marks
   aDefine h-parameters of a transistor.
   How to answer

   • Define h-parameters with input-output equations $V_1=h_{11}I_1+h_{12}V_2$, $I_2=h_{21}I_1+h_{22}V_2$
   • Meaning of $h_{ie}, h_{re}, h_{fe}, h_{oe}$
   • Conditions for measurement - short and open circuit
6. 7 Marks
   bDiscuss small signal analysis of transistor using h-parameters.
   How to answer

   • Small-signal hybrid equivalent circuit of transistor
   • Use of h-parameters in analysis
   • Derivation of voltage gain, current gain, input impedance
   • Assumptions of small-signal linear operation
7. 7 Marks
   aExplain the working principle of MOSFET. What are the four elements of the MOSFET?
   How to answer

   • Structure of MOSFET with gate, source, drain, substrate/body
   • Working principle - formation of channel with gate voltage
   • Four elements: gate, source, drain, substrate
   • Enhancement/depletion operation
8. 7 Marks
   bDiscuss the working of transistor as an amplifier.
   How to answer

   • Biasing of transistor in active region for amplification
   • Role of DC bias and AC input signal
   • Phase inversion and voltage gain explanation
   • Circuit diagram with load
9. 7 Marks
   aExplain, how is bandwidth increased by using negative feedback?
   How to answer

   • Effect of negative feedback on gain $A_f = A/(1+A\beta)$
   • Derivation of upper and lower cut-off frequency extension
   • Formula $BW_f = BW \times (1+A\beta)$
   • Explanation of gain-bandwidth trade-off
10. 7 Marks
    bExplain the working of R-C phase shift oscillator.
    How to answer

    • Circuit diagram of R-C phase shift oscillator with three RC sections
    • Barkhausen criterion and 180+180 degree phase shift
    • Expression for frequency of oscillation $f=1/(2\pi RC\sqrt{6})$
    • Working as sustained oscillations
11. 7 Marks
    aDesign the feedback circuit of a Wein Bridge oscillator with $2\,\mathrm{MHz}$ output frequency.
    How to answer

    • Wien bridge feedback network with series-parallel RC
    • Frequency formula $f=1/(2\pi RC)$ for $2\,\mathrm{MHz}$
    • Selection of R, C values to get 2 MHz
    • Circuit diagram with op-amp and gain condition 3
12. 7 Marks
    bExplain the working of differential amplifier.
    How to answer

    • Circuit of differential amplifier with two transistors and emitter resistor
    • Differential and common mode operation
    • Voltage gain and CMRR concept
    • Waveforms/output explanation
13. 7 Marks
    aExplain the operation of a two level clipper circuit.
    How to answer

    • Circuit of two level clipper with diodes and reference voltages
    • Clipping action above upper and below lower levels
    • Transfer characteristics and output waveforms
    • Types - biased clipper
14. 7 Marks
    bWith the help of internal circuit diagram of IC555 explain the operation of a stable multivibrator. Derive the expression for frequency of oscillation.
    How to answer

    • Internal block diagram of IC555 - comparators, flip-flop, discharge transistor
    • Astable multivibrator connection with R_A, R_B, C
    • Charging-discharging operation and waveforms
    • Derivation of $f = 1.44/((R_A+2R_B)C)$
15. 7 Marks
    aState and explain characteristics of an ideal Op-Amp. Compare ideal Op-Amp and practical Op-Amp.
    How to answer

    • List ideal Op-Amp characteristics - infinite gain, impedance, zero offset
    • Explain each characteristic briefly
    • Compare ideal vs practical values in table form
    • Conclusion on deviations
16. 7 Marks
    bExplain the operation of Op-Amp integrator and differentiator circuits.
    How to answer

    • Op-Amp integrator circuit with R input, C feedback and $V_o = -1/RC \int V_i dt$
    • Op-Amp differentiator circuit with C input, R feedback and $V_o = -RC dV_i/dt$
    • Working with waveforms
    • Circuit diagrams for both