ece 2101 analog pyq

ECE 2101: Analog Electronics — 10-Year Master PYQ Bank (2015–2025)

This document is the systematically categorized, atomic-decomposed question bank extracted verbatim from the Khulna University of Engineering & Technology (KUET) semester-final exam sheets (2015–2025).

Organization Guidelines:

• Definitions First: All definitions and fundamental concept questions appear at the top of every chapter.
• Atomic Decomposition: Compound multi-part exam questions are split into self-contained atomic prompts.
• Deduplication & Year Merging: Identical and equivalent conceptual prompts across years are merged with consolidated appearance years.
• Distinct Numerical Problems: Problems with different numerical parameters remain strictly separated.
• Math Formatting: All mathematical expressions, parameters, and component values are formatted in KaTeX math ($...$).

---

1. Tuned Amplifiers

1.1 Definitions & Core Terminology

Question / Prompt + [Marks] + (Figure ref)	Year(s) of Appearance
Define the term “Tuned Amplifier”. Why is a tuned amplifier not suitable for audio frequency (low frequency) amplification?	2017, 2018, 2022, 2024, 2025
Define the term “Tuned Amplifier”. Explain the tuned amplifier circuit with its industrial and communication applications.	2017, 2019, 2021
When does a parallel tuned resonant circuit behave as a purely resistive, capacitive, or inductive load?	2023
Define the Quality Factor ($Q$-factor) of a resonant circuit. What is the effect of $Q$ on the resonance curve? Why is the quality factor kept as high as possible in tuned circuits?	2015, 2016, 2018, 2022, 2023, 2024
Define the types of coupling in a double-tuned amplifier (loose coupling, critical coupling, and tight coupling).	2015, 2017, 2018, 2021, 2023, 2025

1.2 Resonance Principles, Derivations & Explanations

Question / Prompt + [Marks] + (Figure ref)	Year(s) of Appearance
Explain the LC parallel resonance circuit. Draw the phasor/phase diagram of a parallel resonance circuit and prove mathematically and graphically that resonance occurs when the circuit power factor is unity ($\cos \theta =1$). [06+08]	2015, 2016, 2018, 2020
Derive the expression for the resonance frequency ($f_r=\frac{1}{2\pi }\sqrt{\frac{1}{LC}-\frac{R^2}{L^2}}$) of a parallel LC circuit containing an inductor with winding resistance $R$. State the electrical characteristics of a parallel resonance circuit under resonance conditions.	2019, 2020, 2022
Deduce the simplified relationship of the resonance frequency with the inductance and capacitance of an ideal parallel LC circuit where winding resistance $R$ is negligible ($R\approx 0$).	2025
Prove graphically that the bandwidth of a tuned circuit is directly proportional to the resistance of the inductor, and selectivity is inversely proportional to the resistance of the inductor.	2016, 2019
Explain the AC equivalent circuit of a single-tuned amplifier and analyze the voltage gain in terms of three input frequency conditions: (i) $f_{in}>f_r$, (ii) $f_{in}=f_r$, and (iii) $f_{in}<f_r$.	2017, 2021, 2022, 2023, 2024
Explain the operation of a double-tuned amplifier (DTA). How does coupling affect the frequency response and selectivity of a double-tuned amplifier? Graphically show that loose coupling provides better frequency response than tight coupling.	2015, 2017, 2018, 2019, 2021, 2023, 2025

1.3 Comparisons, Advantages & Schematics

Question / Prompt + [Marks] + (Figure ref)	Year(s) of Appearance
What are the differences between a single-tuned amplifier and a double-tuned amplifier? Mention the advantages of a double-tuned amplifier (DTA).	2015, 2017, 2025
Draw the complete circuit schematic and AC equivalent circuit of a BJT Single-Tuned Amplifier.	2017, 2021, 2022, 2023, 2024
Draw the frequency response curve of an ideal tuned amplifier and discuss its characteristics.	2023

1.4 Design & Numerical Problems

Question / Prompt + [Marks] + (Figure ref)	Year(s) of Appearance
For the single-tuned amplifier shown in Fig. 1(d), determine: (i) resonant frequency, (ii) the $Q$ of the tank circuit, and (iii) bandwidth of the amplifier. Given: coupling capacitor $C_{in}=0.1\mu \text{F}$, tank capacitance $C=0.1\mu \text{F}$, inductance $L=33\text{ mH}$, winding resistance $R=25\Omega$, collector resistor $R_C=R_L=10\text{ k}\Omega$. (Refer to Fig. 1(d))	2015
A tank circuit of a tuned amplifier has a capacitance of $0.1\mu \text{F}$ and inductance of $33\text{ mH}$ plus a winding resistance of $25\Omega$. Determine: (i) the resonant frequency, (ii) the $Q$ of the tank circuit, and (iii) bandwidth of the amplifier.	2018
It is desired to obtain a bandwidth of $250\text{ kHz}$ at an operating frequency of $10\text{ MHz}$ using a double-tuned circuit. What value of coefficient of coupling ($k$) should be used?	2016, 2021, 2024
The dynamic impedance of a parallel resonant circuit is $500\text{ k}\Omega$. The circuit consists of a $250\text{ pF}$ capacitor in parallel with a coil of resistance $100\Omega$. Calculate: (i) the coil inductance, (ii) the resonant frequency, and (iii) $Q$-factor of the circuit.	2017, 2020
A parallel resonant circuit has a capacitance of $100\text{ pF}$ in one branch and inductance of $100\mu \text{H}$ plus a resistance of $10\Omega$ in the parallel branch. If the supply voltage is $10\text{ V}$, calculate: (i) resonance frequency, (ii) impedance of the circuit, and (iii) line current at resonance.	2018, 2019
A parallel resonant circuit has a capacitance of $250\text{ pF}$ in one branch and inductance of $1.25\text{ mH}$ plus a resistance of $10\Omega$ in the parallel branch. Find: (i) resonant frequency, (ii) impedance of the circuit at resonance, and (iii) $Q$-factor of the circuit.	2022
A tuned amplifier has a parallel LC circuit. One branch has a capacitor of $100\text{ pF}$ and the other branch has an inductance of $1\text{ mH}$ plus a resistance of $25\Omega$. Determine: (i) the resonant frequency, and (ii) $Q$ of the tank circuit.	2023
An inductor of resistance $10\Omega$ and inductance $100\text{ mH}$ is in parallel with a $10\text{ nF}$ capacitor. Find: (i) the resonant frequency, (ii) the $Q$-factor, and (iii) the bandwidth.	2025

---

2. Oscillators

2.1 Definitions & Fundamentals

Question / Prompt + [Marks] + (Figure ref)	Year(s) of Appearance
Define an electronic Oscillator. What is a sinusoidal oscillator? What are the advantages of using an oscillator as a frequency/function generator?	2015, 2016, 2019, 2020, 2022, 2023, 2024, 2025
State the requirements and conditions necessary to work a transistor as an oscillator. Write down the names of commonly used transistor oscillator circuits.	2015, 2016, 2018, 2019, 2020, 2023, 2024
Describe the main components and essential parts required for designing a transistor oscillator (tank circuit, amplifier, feedback network), and briefly discuss the functions of each part.	2021, 2022, 2023, 2024
What is the Barkhausen Criterion? Why is it important for oscillator circuits? Give the graphical/phasor explanation of the Barkhausen criterion.	2016, 2017, 2018
Define Piezoelectric Crystal and the Piezoelectric effect.	2015

2.2 LC & Tuned Oscillators

Question / Prompt + [Marks] + (Figure ref)	Year(s) of Appearance
Explain the principle of an oscillatory circuit. Describe the conditions and process of generating undamped oscillations from an LC tank circuit.	2015, 2016, 2018, 2021, 2022, 2024, 2025
Draw the circuit diagram and explain the operation of a Tuned Collector Oscillator.	2019
Draw the circuit diagram and describe the circuit operation and feedback fraction ($\beta =L_2/L_1$) of a Hartley Oscillator.	2017, 2022
Draw the circuit diagram and describe the circuit operation and feedback fraction ($\beta =C_1/C_2$) of a Colpitts Oscillator.	2018, 2023, 2025
Compare Colpitts and Hartley oscillators in terms of tank components, feedback method, and frequency range.	2020

2.3 RC & Crystal Oscillators

Question / Prompt + [Marks] + (Figure ref)	Year(s) of Appearance
Explain the principle of the phase-shift network in an RC Phase-Shift Oscillator. Explain the operation of a phase-shift oscillator circuit. [06+06]	2016, 2017, 2018, 2024
Explain the operation of a Wien Bridge Oscillator. What is the specific function of the tungsten lamp in stabilizing output amplitude? List the advantages and disadvantages of the Wien Bridge oscillator.	2015, 2019, 2024, 2025
Explain the electrical equivalent circuit of a quartz crystal. Explain the frequency response and reactance curve of a crystal for series and parallel resonance conditions.	2015, 2016, 2017, 2019, 2021, 2025
What are the limitations of LC and RC oscillators that make crystal oscillators preferred?	2015, 2016, 2017, 2021, 2025

2.4 Relaxation & UJT Oscillators

Question / Prompt + [Marks] + (Figure ref)	Year(s) of Appearance
Explain the operation of a UJT Relaxation Oscillator, draw its schematic and output sawtooth waveform, and derive the equation for the frequency of the generated sawtooth output ($f=\frac{1}{RC\ln (1/(1-\eta ))}$).	2017, 2022, 2025

2.5 Design & Numerical Problems

Question / Prompt + [Marks] + (Figure ref)	Year(s) of Appearance
Determine: (i) operating frequency ($f_0$) and (ii) feedback fraction ($m_v$) for the Colpitts oscillator shown in Fig. 2(d) / Figure 3(c). Given: $C_1=0.001\mu \text{F},C_2=0.01\mu \text{F},L=15\mu \text{H}$. (Refer to Fig. 2(d) / Figure 3(c))	2015, 2019, 2022, 2024
What is the frequency of oscillation in the given oscillator circuit? What is the feedback fraction? How much voltage gain does the circuit need to start oscillation? (Refer to Fig. 2(d))	2017
In the Wien bridge oscillator shown in Fig. 2(d), $R_1=R_2=220\text{ k}\Omega$ and $C_1=C_2=250\text{ pF}$. Determine the frequency of oscillation. (Refer to Fig. 2(d))	2016
Consider an inductor of (last two digits of your Roll / 4) mH. Choose the capacitor values ($C_1,C_2$) in a Colpitts oscillator so that $f_r=1\text{ MHz}$ and $m_v=0.25$.	2020
A $1\text{ mH}$ inductor is available. Choose the capacitor values ($C_1,C_2$) in a Colpitts oscillator so that $f=1\text{ MHz}$ and $m_v=0.25$.	2025
A $1\text{ pF}$ capacitor is available. Choose the inductor values ($L_1,L_2$) in a Hartley oscillator so that $f=1\text{ MHz}$ and $m_v=0.2$.	2023
The AC equivalent circuit of a crystal has these values: $L=1\text{ H},C=0.001\text{ pF},R=1000\Omega$, and $C_m=20\text{ pF}$. Calculate the series resonant frequency ($f_s$) and parallel resonant frequency ($f_p$) of the crystal.	2017, 2018, 2022, 2024
The AC equivalent circuit of a crystal has these values: $L=1\text{ H},C=0.001\text{ pF},R=100\Omega$, and $C_m=20\text{ pF}$. Calculate $f_s$ and $f_p$ of the crystal.	2025
The AC equivalent circuit of a crystal has these values: $L=2\text{ H},C=0.01\text{ pF},R=1000\Omega$, and $C_m=20\text{ pF}$. Calculate $f_s$ and $f_p$ of the crystal.	2019

---

3. Feedback Amplifiers

3.1 Definitions, Topologies & Distortion

Question / Prompt + [Marks] + (Figure ref)	Year(s) of Appearance
Define feedback as applied to electronic amplifiers. Why is negative feedback necessary in practical amplifiers despite reducing the overall voltage gain? What are its primary advantages?	2015, 2025
Classify the four basic feedback connection types (Voltage-Series, Voltage-Shunt, Current-Series, Current-Shunt) and write down the properties and characteristics of each feedback connection type.	2019, 2022, 2024
What is nonlinear distortion (harmonic distortion)? Explain why nonlinear distortion occurs in amplifiers and how negative feedback reduces it. Prove that the total harmonic distortion of a feedback amplifier is lower than that without feedback by a factor of $(1+\beta A)$. [05+10]	2016, 2017, 2021, 2025

3.2 Principles, Gain Stability & Bandwidth

Question / Prompt + [Marks] + (Figure ref)	Year(s) of Appearance
Prove that the gain of an amplifier with negative feedback is more stable than the gain without feedback. Prove that the gain stability of an amplifier with feedback is '$\beta A$' times higher than that of the amplifier without feedback (desensitized by a factor of $1+\beta A$).	2018, 2019, 2021, 2023, 2025
Prove that the closed-loop voltage gain of a practical feedback amplifier is inversely proportional to the feedback factor ($A_F\approx 1/\beta$) when loop gain is very large ($\beta A\gg 1$).	2015, 2016, 2018, 2020
Explain the general effects of negative feedback on amplifier parameters: gain, bandwidth, input impedance, output impedance, and noise. How/why does negative feedback increase the bandwidth of an amplifier?	2015, 2016, 2017, 2020, 2022, 2023, 2024

3.3 Input & Output Impedance Derivations

Question / Prompt + [Marks] + (Figure ref)	Year(s) of Appearance
Derive the expression for input impedance with feedback ($Z_{inF}=Z_{in}(1+\beta A)$) of a Voltage-Series feedback amplifier with necessary diagram.	2021, 2022, 2024
Derive the expressions for input impedances of both Voltage-Series ($Z_{inF}=Z_{in}(1+\beta A)$) and Voltage-Shunt ($Z_{inF}=\frac{Z_{in}}{1+\beta A}$) feedback circuits.	2017
Derive the expressions for the output impedance of Voltage-Series ($Z_{outF}=\frac{Z_{out}}{1+\beta A}$) and Current-Series ($Z_{outF}=Z_{out}(1+\beta A)$) feedback circuits.	2016, 2018, 2021
Derive the expression for the output impedance of a Current-Series feedback amplifier ($Z_{outF}=Z_{out}(1+\beta A)$) with necessary diagram.	2019, 2023

3.4 Mathematical Problems

Question / Prompt + [Marks] + (Figure ref)	Year(s) of Appearance
The overall gain of a multistage amplifier without feedback is $140$. When negative voltage feedback is applied, the gain is reduced to $17.5$. Find the fraction of the output that is fed back to the input ($\beta$).	2015, 2021
An amplifier has an open-loop gain $A=100,000$. A negative feedback of $10\text{ dB}$ is applied. Find: (i) voltage gain with feedback ($A_F$), and (ii) value of feedback fraction ($\beta$).	2015, 2016, 2019
An amplifier is required with a voltage gain of $100$ which does not vary by more than $1\%$. If it is to use negative feedback with a basic amplifier whose voltage gain can vary by $20\%$, determine the minimum voltage gain required and the feedback factor ($\beta$).	2016, 2020
An amplifier has an open-circuit voltage gain of $70\text{ dB}$ and an output resistance of $1.5\text{ k}\Omega$. Determine the minimum value of load resistance so that the voltage gain is not more than $67\text{ dB}$.	2017
Calculate the gain without and with feedback for the FET amplifier circuit shown in Fig. 4(d) / Fig. 3(c) given circuit values: $R_1=80\text{ k}\Omega ,R_2=20\text{ k}\Omega ,R_o=10\text{ k}\Omega ,R_D=10\text{ k}\Omega$, and transconductance $g_m=4000\mu \text{S}$. (Refer to Fig. 4(d) / Figure 3(c))	2018, 2021, 2023
The gain of an amplifier without feedback is $50$, whereas with negative voltage feedback it falls to $25$. If due to aging the basic amplifier gain falls to $40$, find the percentage reduction in stage gain: (i) without feedback, and (ii) with negative feedback.	2022
An amplifier has a voltage amplification $A_v=100$ and a fraction $m_v=0.1$ of its output is fed back in opposition to the input. Calculate the percentage change in the gain of the system if $A_v$ falls by $6\text{ dB}$ due to aging.	2023, 2024, 2025

---

4. Operational Amplifiers (Op-Amps)

4.1 Definitions & Ideal Characteristics

Question / Prompt + [Marks] + (Figure ref)	Year(s) of Appearance
Define the term “Operational Amplifier” (Op-Amp) and “Integrated Circuit” (IC).	2016, 2017, 2020, 2023, 2024
Define: (i) Input offset voltage, (ii) Input offset current, (iii) Slew rate, and (iv) Input bias current of an Op-Amp.	2015
Define the Common-Mode Rejection Ratio (CMRR) and Slew Rate of an Op-Amp.	2015, 2016, 2017, 2018, 2021, 2022
Define the concept of “Virtual Ground” for an inverting amplifier and “Virtual Short” for a non-inverting amplifier configuration.	2015, 2017, 2021
State and list the electrical characteristics of an ideal Op-Amp. Write down the practical benefits of having infinite input resistance, zero output resistance, infinite open-loop gain, infinite CMRR, and infinite slew rate.	2016, 2018, 2019, 2021, 2023
What is offset voltage in an Op-Amp? Briefly explain the offset voltage adjustment process to null the output.	2023, 2025

4.2 Architecture, Configurations & Feedback Principles

Question / Prompt + [Marks] + (Figure ref)	Year(s) of Appearance
Explain and draw the block diagram of the four basic building blocks of a typical Op-Amp architecture.	2018, 2021
Explain the single-ended and double-ended operations of an Op-Amp using input voltage configurations.	2015, 2017
Draw and explain the equivalent circuit and ideal voltage transfer curve of an Op-Amp.	2019, 2020, 2022, 2024, 2025
Why is an open-loop Op-Amp not suitable for linear applications? Explain why negative feedback is practical for linear applications, and state the applications of positive feedback.	2017, 2019
”Negative feedback in Op-Amp stabilizes gain but increases bandwidth” — Explain.	2025
When is a non-inverting amplifier called a “voltage follower”? Explain the circuit diagram of a voltage follower in this configuration and discuss its design benefits and applications.	2018, 2024
Discuss the three open-loop configurations of an Op-Amp acting as a high-gain amplifier. How can an Op-Amp act as a switching circuit?	2024, 2025

4.3 Derivations & Arithmetic Applications

Question / Prompt + [Marks] + (Figure ref)	Year(s) of Appearance
Derive the expression for the closed-loop voltage gain ($A_f=1+R_F/R_1$) of a non-inverting amplifier configuration.	2015
Prove that the closed-loop voltage gain of a non-inverting Op-Amp amplifier is lower than its open-loop voltage gain.	2018, 2022
Derive the expression for the closed-loop voltage gain ($A_f=-R_F/R_1$) of an inverting amplifier configuration with necessary diagram.	2021, 2022
Derive the expression for scaling operation using an inverting Op-Amp configuration. Evaluate if multiplication can be performed in this setup.	2024
Distinguish between Common-Mode Gain ($A_{cm}$) and Differential Gain ($A_d$) of an Op-Amp.	2019
Prove mathematically that, depending on the relationship between the feedback resistor ($R_F$) and input resistors ($R_a,R_b,R_c$), a multi-input Op-Amp circuit can be used as a summing amplifier, a scaling amplifier, or an averaging amplifier.	2017
Explain the differences between: (i) inverting and differential summing amplifiers, and (ii) inverting and non-inverting averaging amplifiers.	2016
Describe the operation of an averaging amplifier utilizing a non-inverting configuration of an Op-Amp.	2023, 2025
In the same resistor configurations of an inverting and non-inverting amplifier, which configuration has higher closed-loop gain?	2025

4.4 Integrators & Differentiators

Question / Prompt + [Marks] + (Figure ref)	Year(s) of Appearance
Define an Integrator circuit. Explain how an Op-Amp circuit acts as an integrator with circuit diagram, and derive the expression for the output voltage ($v_o(t)=-\frac{1}{R_1{C}_F}\int v_{in}dt$).	2015, 2017, 2019, 2020, 2021, 2023
What are the practical limitations of a basic integrator circuit, and how are these limitations solved in practical integrators using parallel feedback resistors?	2024
Write down the applications of a differentiator. How does an Op-Amp act as a differentiator circuit?	2025
What are the practical problems associated with a basic differentiator circuit (noise susceptibility and high-frequency instability)? Explain the process of reducing these problems in a practical differentiator circuit using series limiting resistors and parallel capacitors.	2021, 2023

4.5 Design & Numerical Problems

Question / Prompt + [Marks] + (Figure ref)	Year(s) of Appearance
The 741C Op-Amp is connected as a non-inverting amplifier as shown in Fig. 5(d) with $R_1=1\text{ k}\Omega ,R_F=10\text{ k}\Omega ,A=200,000,R_i=2\text{ M}\Omega ,R_o=75\Omega ,f_o=5\text{ Hz}$, supply voltage = $\pm 15\text{ V}$, output voltage swing = $\pm 13\text{ V}$. Compute $A_F,R_{iF},R_{oF},f_F$, and $V_{ooT}$. (Refer to Fig. 5(d))	2015
For the inverting amplifier of Fig. 5(d), $R_1=470\Omega$ and $R_F=4.7\text{ k}\Omega$. Calculate $A_F,R_{iF},R_{oF},f_F$, and $V_{ooT}$ for a 741C Op-Amp with $A=200,000,R_i=2\text{ M}\Omega ,R_o=75\Omega ,f_o\approx 5\text{ Hz}$, supply voltage = $\pm 15\text{ V}$, output voltage swing = $\pm 13\text{ V}$. (Refer to Fig. 5(d))	2017
A 741C is configured as a non-inverting amplifier with $A=400,000,R_1=470\Omega ,R_I=33\text{ M}\Omega ,R_F=4.7\text{ k}\Omega ,R_o=60\Omega$, supply voltage = $\pm 15\text{ V}$, max output voltage swing = $\pm 13\text{ V},\text{UGB}=0.6\text{ MHz}$. Compute closed-loop parameters $A_F,R_{iF},R_{oF},f_F$, and $V_{ooT}$. (Refer to Figure of Q. 4(c))	2020
For the circuit shown in Fig. 5(b), assume ideal Op-Amp: (i) Name the feedback topology and calculate the feedback factor, (ii) Calculate $V_o/V_i$, (iii) Assume $R_2$ is replaced by a capacitor; draw the circuit diagram and find $V_o(t)$. (Refer to Fig. 5(b))	2016
Determine the output voltage of an Op-Amp for input voltages $V_{i1}=150\mu \text{V}$ and $V_{i2}=140\mu \text{V}$, differential gain $A_d=4000$, and CMRR value of: (i) $100$, and (ii) $10^5$.	2016, 2018
Specifications for the differential amplifier of Fig. 5(d): $R_1=R_3=680\Omega ,R_F=R_2=6.8\text{ k}\Omega$, inputs $V_x=-1.5{\text{ V}}_{\text{pp}}$ and $V_y=-2{\text{ V}}_{\text{pp}}$ sine waves at $1\text{ kHz}$. Op-Amp is IC 741C. Calculate: (i) voltage gain and input resistance, and (ii) output voltage, assuming initially nulled ($V_{oo}=0\text{ V}$). (Refer to Fig. 5(d))	2016
In the circuit of Fig. 5(d), $R_1=R_2=1\text{ k}\Omega ,R_F=R_3=10\text{ k}\Omega$, using a 741C Op-Amp: (i) Calculate gain and input resistance, (ii) Calculate output voltage $v_o$ if $v_x=2.7{\text{ V}}_{\text{pp}}$ and $v_y=3{\text{ V}}_{\text{pp}}$ sine wave at $100\text{ Hz}$. (Refer to Fig. 5(d))	2018
For the circuit shown in Fig. 5(d), assume ideal Op-Amp: (i) Identify the feedback topology, (ii) Calculate $v_o/v_i$, (iii) Relate closed-loop gain with open-loop gain. (Refer to Fig. 5(d))	2019
Determine the output voltage $V_o$ in an Op-Amp based differential amplifier using an LM741 with supply voltage $\pm 15\text{ V}$.	2024
In the circuit of Fig. 6(d), $R_1{C}_F=1\text{ s}$, and the input is a step (DC) voltage. Determine the output voltage and sketch it, assuming the Op-Amp is initially nulled. (Refer to Fig. 6(d))	2017
In the integrator circuit of Fig. 7(d), the input is a sine wave with peak-to-peak amplitude of $5\text{ V}$ at $1\text{ kHz}$. Draw the output voltage waveform if $R_1{C}_F=0.1\text{ ms}$ and $R_F=10R_1$, assuming voltage across $C_F$ is initially zero. (Refer to Fig. of Q. 7(d))	2021
Design a differentiator circuit to process an input signal varying from $10\text{ Hz}$ to $1\text{ kHz}$.	2015, 2016, 2018, 2022
Design a differentiator circuit that will differentiate an input signal with $f_{\max }=100\text{ Hz}$.	2021
Design a practical integrator circuit to properly process input sinusoidal waveforms up to $1\text{ kHz}$ given an input amplitude of $10\text{ mV}$.	2023
Design and draw a circuit diagram with an Op-Amp amplifier having three input signals of $1{\text{ V}}_{\text{pp}}$ at $100\text{ Hz}$ each to produce an output signal of $30{\text{ V}}_{\text{pp}}$ at $100\text{ Hz}$.	2018

---

5. Multivibrators and 555 Timers

5.1 Definitions & Multivibrator Operations

Question / Prompt + [Marks] + (Figure ref)	Year(s) of Appearance
Define a “Multivibrator” and classify its modes (astable, monostable, bistable).	2015, 2017, 2019, 2022, 2024
What do you mean by a speed-up capacitor and what is its role in BJT switching acceleration?	2017
What are the differences between an oscillator and a multivibrator?	2016
Explain the operation of a transistor-based bistable multivibrator with required circuit diagram.	2015, 2017, 2019
Explain the operation of a transistor-based astable multivibrator. [03+06]	2016
Explain the operation of a transistor-based monostable multivibrator with circuit diagram and mention its applications.	2018, 2023

5.2 555 Timer Operations & Waveforms

Question / Prompt + [Marks] + (Figure ref)	Year(s) of Appearance
Draw and explain the internal block diagram of the 555 Timer IC.	2016, 2017, 2018, 2020
Explain the Voltage Controlled Oscillator (VCO) operation of a 555 timer with necessary block diagram.	2019
How does charging and discharging occur in the astable operation of a 555 timer? Show that the timing capacitor voltage oscillates strictly between $V_{CC}/3$ and $2V_{CC}/3$.	2025
How can a $50\%$ duty cycle be achieved in the astable operation of a 555 timer? Draw the circuit diagram and explain with necessary design equations.	2024, 2025

5.3 Design & Numerical Problems

Question / Prompt + [Marks] + (Figure ref)	Year(s) of Appearance
Design a 555 astable multivibrator to yield a pulse repetition frequency (PRF) of $2\text{ kHz}$ and duty cycle of $66\%$ given supply voltage $V_{CC}=18\text{ V}$.	2015
In the monostable circuit of Fig. 7(d), $R_A=10\text{ k}\Omega$ and output pulse width $t_p=10\text{ ms}$. Determine the value of capacitance $C$. (Refer to Fig. 7(d))	2016
In the monostable circuit of Fig. 7(d), $R_1=10\text{ k}\Omega$ and output pulse width $t_p=100\text{ ms}$. Determine the value of capacitance $C$. (Refer to Fig. 7(d))	2018
In the astable multivibrator of Fig. 7(d) / Fig. 5(c), $R_A=2.2\text{ k}\Omega ,R_B=3.9\text{ k}\Omega$, and $C=0.1\mu \text{F}$. Determine: (i) positive pulse width ($t_c$), (ii) negative pulse width ($t_d$), and (iii) free-running frequency ($f_o$). (Refer to Fig. 7(d) / Fig. 5(c))	2017, 2020
In Fig. 6(d), $V_{CC}=12\text{ V},R=33\text{ k}\Omega$, and $C=0.47\mu \text{F}$. Determine: (i) minimum trigger voltage that produces an output pulse, (ii) maximum capacitor voltage, and (iii) width of the output pulse. (Refer to Fig. 6(d))	2019

---

6. Active Filters

6.1 Definitions & Fundamentals

Question / Prompt + [Marks] + (Figure ref)	Year(s) of Appearance
Define a “Filter” in electronic systems.	2024
What is meant by the Order of a Filter? Explain its relationship with stopband roll-off rate (dB/decade).	2015, 2016, 2017, 2019, 2023
State the key advantages of active filters over passive filters (elimination of heavy inductors, no loading effect, gain capability, easier tuning).	2015, 2016, 2019, 2023, 2024
Define “Cut-off Frequency” ($f_C$) as applied to filters.	2016, 2017
Define the terms "$20\text{ dB/decade}$" and "$40\text{ dB/decade}$" roll-off in the stopband of a filter.	2018
Define: (i) Transition time, (ii) Settling time, (iii) Symmetrical triggering, (iv) Unsymmetrical triggering, and (v) Notch filter.	2015

6.2 Theory, Derivations & Comparisons

Question / Prompt + [Marks] + (Figure ref)	Year(s) of Appearance
Note down the pros and cons of the Butterworth filter approximation compared to Chebyshev or Bessel types.	2017
What are the differences between band-pass and band-stop active filters? [02+06]	2016, 2017
Derive the gain magnitude ($	A_v
Draw the circuit diagram of a first-order active high-pass filter and plot its frequency response curve.	2021

6.3 Design & Numerical Problems

Question / Prompt + [Marks] + (Figure ref)	Year(s) of Appearance
Design an active low-pass filter at a cut-off frequency of $1\text{ kHz}$ with a passband gain of $2$.	2016, 2018
Design an active high-pass filter at a cut-off frequency of $1\text{ kHz}$ with a passband gain of $2$. Also, plot the frequency response curve clearly labeling the cutoff region.	2017, 2020, 2022
Design a $20\text{ dB/decade}$ low-pass filter to have a cut-off frequency of $2\text{ kHz}$ and a passband gain of $1$.	2021
Design a second-order low-pass filter at a cutoff frequency of $1.2\text{ kHz}$.	2022
Design a low-pass filter at a cutoff frequency of $1\text{ kHz}$ with a passband gain of $2$. Using the frequency scaling technique, convert the cutoff frequency to $1.6\text{ kHz}$.	2021, 2022, 2023
Design a wide band-pass filter with $f_L=200\text{ Hz},f_H=1\text{ kHz}$, and a passband gain of $4$. Calculate the $Q$-value of the filter.	2019, 2023, 2024
Design a wide band-pass filter with $f_L=200\text{ Hz},f_H=3\text{ kHz}$, and a passband gain of $3.5$. Calculate the $Q$-value of the filter.	2025

---

7. Wave Shaping Circuits

7.1 Definitions & Fundamentals

Question / Prompt + [Marks] + (Figure ref)	Year(s) of Appearance
Define a Comparator Circuit. Write down its five basic uses in analog signal processing.	2023, 2024
Define “Schmitt Trigger” (regenerative comparator). Why is a Schmitt trigger known as a regenerative comparator?	2015, 2016, 2017, 2018, 2020
What are the differences between a basic comparator and a Schmitt trigger?	2016, 2018
Define Clipping and Clamping circuits, classify clippers, and explain their common applications and why they are used in electronic systems.	2015, 2016, 2018, 2019, 2020, 2021

7.2 Principles & Schmitt Trigger Operations

Question / Prompt + [Marks] + (Figure ref)	Year(s) of Appearance
How can an Op-Amp comparator circuit act as a voltage-level detector? Draw the circuit diagram of a $+10\text{ V}$ voltage-level detector with an Op-Amp.	2019
Explain the operation of a window detector (window comparator) circuit with necessary diagram, and write down its practical applications.	2019, 2022, 2023
Explain the operation and input-output response of a Schmitt trigger circuit with necessary diagram and hysteresis properties.	2015, 2017, 2020, 2021, 2022
”Schmitt trigger converts an irregular-shaped waveform to a square pulse” — Explain with necessary derivation.	2025

7.3 Graphical Waveshapes & Calculation Problems

Question / Prompt + [Marks] + (Figure ref)	Year(s) of Appearance
Draw the output waveshapes for the diode clipper circuits shown in Fig. 8(c) / Fig. 6(c). Assume diodes are ideal. (Refer to Fig. 8(c) / Fig. 6(c))	2015, 2016, 2017, 2018, 2019, 2020
Draw the output waveshapes for the diode clamper circuits shown in Fig. 8(d) / Fig. 8(a) / Fig. 8(c). Assume diodes are ideal. (Refer to Fig. 8(d) / Fig. 8(a) / Fig. 8(c))	2016, 2019, 2021, 2022
Draw the output waveform for the circuit shown in Figure 6(b), where the input is a $20{\text{ V}}_{\text{pp}}$ sinusoidal wave at $50\text{ Hz}$. (Refer to Figure 6(b))	2024
Calculate the Upper Threshold Voltage ($V_{UT}$), Lower Threshold Voltage ($V_{LT}$), and Hysteresis Voltage ($V_H$) of a Schmitt trigger circuit, given that $R_1=R_2=5\text{ k}\Omega$ and output saturation voltage $\pm V_{\text{sat}}=\pm 14\text{ V}$.	2024, 2025

---

8. Phase Locked Loop (PLL)

8.1 Definitions & Fundamentals

Question / Prompt + [Marks] + (Figure ref)	Year(s) of Appearance
Define the term “Phase Locked Loop” (PLL).	2015, 2016, 2017, 2018, 2022, 2023
What are the applications of a Phase Locked Loop (PLL) in communication systems (e.g., FM demodulation, frequency synthesis, FSK decoder, AM detection)? [04+04]	2016

8.2 Concepts, Operating Principles & Block Diagrams

Question / Prompt + [Marks] + (Figure ref)	Year(s) of Appearance
With the help of a neat block diagram, explain the construction and operating principle of a Phase Locked Loop (PLL), detailing the function of each sub-block (Phase Detector/Comparator, Low Pass Filter, Error Amplifier, Voltage Controlled Oscillator).	2015, 2017, 2018, 2019, 2022, 2023
Draw the complete block diagram of a Phase Locked Loop (PLL).	2015, 2017, 2018, 2019, 2022, 2023
022