ayesha mam checklist

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Instructor 1: Tuned Amplifiers, Feedback Amplifiers, & Oscillators

Chapter 1: Tuned Amplifiers

Definitions & Core Terminology

• Define the term “Tuned Amplifier” and list its key industrial and communications applications. [PYQ: 2017, 2019, 2021, 2022, 2024, 2025] [Heavily Tested]
• Define the Quality Factor ($Q$-factor) of a resonant circuit and state its mathematical relationship with coil parameters. [PYQ: 2015, 2016, 2018, 2022, 2023] [Heavily Tested]
• Define the “selectivity” of a tuned amplifier circuit and explain how it relates to the sharpness of the resonance curve.
• Define the “bandwidth” ($BW$) of a tuned circuit in terms of half-power (3 dB) cutoff frequencies ($f_1$ and $f_2$).
• Define the terms “loose coupling,” “tight (or close) coupling,” and “critical coupling” as they apply to double-tuned amplifier circuits.

Core Principles & Explanations

• Explain the working principle of a parallel LC resonant tank circuit.
• Explain why tuned circuits are not used to amplify low frequencies (audio frequencies) and discuss the physical size constraints of $L$ and $C$ components at low frequencies. [PYQ: 2017, 2018, 2022, 2024, 2025] [Heavily Tested]
• Explain when a parallel resonant circuit behaves as a purely resistive, capacitive, or inductive load depending on the input frequency $f_{in}$ relative to the resonant frequency $f_r$. [PYQ: 2023]
• State and explain the electrical characteristics of a parallel resonance circuit under resonance conditions. [PYQ: 2019, 2020]
• Explain the operating principle of a single-tuned BJT amplifier.
• Explain the operating principle of a double-tuned BJT amplifier. [PYQ: 2018, 2019]
• Explain how the selectivity and bandwidth of a double-tuned amplifier depend on the degree of coupling between the primary and secondary coils. [PYQ: 2015, 2017, 2018, 2021, 2023, 2025] [Heavily Tested]
• State the key advantages of tuned amplifiers over conventional resistive-load amplifiers (e.g., small power loss, high efficiency, high selectivity, and lower required collector supply voltage $V_{CC}$).
• State the advantages of a double-tuned amplifier (DTA) over a single-tuned amplifier. [PYQ: 2025]

Derivations

• Derive the mathematical expression for the resonant 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 a winding resistance $R$. [PYQ: 2019, 2020, 2022, 2025] [Heavily Tested]
• Deduce the simplified relationship of the resonant frequency with the inductance and capacitance of an ideal parallel LC circuit where winding resistance $R$ is negligible ($R\approx 0$). [PYQ: 2025]
• Derive the expression for the bandwidth ($BW=\frac{f_r}{Q}$) of a parallel resonant tuned circuit.
• Derive the AC voltage gain equation of a single-tuned amplifier at resonant frequency.

Proofs

• Prove mathematically and graphically that a parallel resonance circuit achieves resonance when the circuit power factor is unity ($\cos \theta =1$). [PYQ: 2015, 2016, 2018, 2020] [Heavily Tested]
• 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. [PYQ: 2016, 2019]

Comparison/Difference Tables

• Differentiate between single-tuned amplifiers and double-tuned amplifiers in a structured comparison table. [PYQ: 2015, 2017]
• Compare the frequency response curves and selectivity of loose coupling versus tight coupling in double-tuned circuits.

Diagrams & Circuits

• Draw the complete circuit schematic of a BJT Single Tuned Amplifier. [PYQ: 2023, 2024]
• Draw the exact AC equivalent circuit of a single-tuned BJT amplifier. [PYQ: 2017, 2021, 2022, 2023, 2024] [Heavily Tested]
• Draw the phase/phasor diagram of a parallel resonant LC circuit under three frequency conditions: resonance ($f_{in}=f_r$), inductive ($f_{in}<f_r$), and capacitive ($f_{in}>f_r$). [PYQ: 2015, 2016, 2018, 2022] [Heavily Tested]
• Draw the frequency response curve of an ideal tuned amplifier and discuss its characteristics. [PYQ: 2023]
• Draw the practical frequency response curve of a tuned amplifier, clearly labeling the half-power (3 dB) points, bandwidth ($BW$), lower cutoff frequency ($f_1$), and upper cutoff frequency ($f_2$).
• Draw the family of frequency response curves for a double-tuned amplifier under loose coupling, critical coupling, and tight coupling conditions. [PYQ: 2015, 2017, 2018, 2021, 2023, 2025] [Heavily Tested]
• Draw the circuit diagram of a Double Tuned BJT Amplifier.

Algorithms & Procedures

• Follow the step-by-step procedure to analyze the AC equivalent circuit of a single-tuned amplifier by evaluating it under three input frequency conditions: (i) $f_{in}>f_r$, (ii) $f_{in}=f_r$, and (iii) $f_{in}<f_r$. [PYQ: 2017, 2021, 2022, 2023, 2024] [Heavily Tested]

Numericals & Calculations

• Solve for (i) resonant frequency, (ii) the $Q$ of the tank circuit, and (iii) bandwidth of the single-tuned amplifier shown in Fig. 1(d) 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 $R_C=R_L=10\text{ k}\Omega$, and transistor biasing resistors. [PYQ: 2015]
• Solve for (i) resonant frequency, (ii) the $Q$ of the tank circuit, and (iii) bandwidth of the tuned amplifier given tank parameters: capacitance $C=0.1\mu \text{F}$ and inductance $L=33\text{ mH}$ plus winding resistance $R=25\Omega$. [PYQ: 2018]
• Solve for (i) the coil inductance, (ii) the resonant frequency, and (iii) $Q$-factor of the circuit given: a parallel resonant circuit dynamic impedance $Z_r=500\text{ k}\Omega$, capacitance $C=250\text{ pF}$ in parallel with a coil of resistance $R=100\Omega$. [PYQ: 2017, 2020, 2022] [Heavily Tested]
• Solve for (i) resonance frequency, (ii) impedance of the circuit, and (iii) line current at resonance given: a parallel resonant circuit with capacitance $C=100\text{ pF}$ in one branch and inductance $L=100\mu \text{H}$ plus a resistance of $R=10\Omega$ in the parallel branch with a supply voltage of $10\text{ V}$. [PYQ: 2018, 2019]
• Solve for (i) the resonant frequency and (ii) $Q$ of the tank circuit given: a tuned amplifier with parallel LC circuit where one branch has a capacitor of $100\text{ pF}$ and the other branch has an inductance of $1\text{ mH}$ plus winding resistance $R=25\Omega$. [PYQ: 2023]
• Solve for (i) the resonant frequency, (ii) the $Q$-factor, and (iii) the bandwidth given: an inductor of resistance $R=10\Omega$ and inductance $L=100\text{ mH}$ in parallel with a $10\text{ nF}$ capacitor. [PYQ: 2025]
• Solve for the value of the coefficient of coupling ($k$) to design a double-tuned amplifier to obtain a bandwidth ($BW$) of $250\text{ kHz}$ at an operating frequency of $10\text{ MHz}$. [PYQ: 2016, 2021, 2024] [Heavily Tested]

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Chapter 2: Feedback Amplifiers

Definitions & Core Terminology

• Define the term “feedback” as applied to electronic amplifiers.
• Define “positive (regenerative) feedback” and “negative (degenerative) feedback.”
• Define the “feedback fraction” (or feedback attenuation factor) $\beta$.
• Define the “loop gain” of a feedback amplifier and explain its significance.
• Define the “desensitivity factor” ($1+\beta A$) of a negative feedback amplifier.
• Define “nonlinear distortion” (or harmonic distortion) and state why it occurs in linear amplifiers. [PYQ: 2021, 2025]
• Define the four basic topologies of feedback connections: Voltage-Series, Current-Series, Voltage-Shunt, and Current-Shunt feedback.

Core Principles & Explanations

• Explain why negative feedback is necessary in practical amplifiers despite reducing the overall voltage gain. [PYQ: 2015, 2025]
• Explain the general effects of negative feedback on amplifier parameters: gain, bandwidth, input impedance, output impedance, noise, and nonlinear distortion. [PYQ: 2015, 2017, 2020, 2022, 2024] [Heavily Tested]
• Explain how negative feedback stabilizes the voltage gain of an amplifier against temperature variations, aging of active components, and supply voltage fluctuations. [PYQ: 2018, 2019]
• Explain why negative feedback increases the bandwidth of an amplifier. [PYQ: 2016]
• Explain the mechanism of nonlinear/harmonic distortion in amplifiers and how negative feedback reduces it. [PYQ: 2016, 2021, 2025]

Derivations

• Derive the mathematical expression for the closed-loop voltage gain ($A_F=\frac{A}{1+\beta A}$) of a feedback amplifier.
• Derive the expression for input impedance with feedback ($Z_{inF}=Z_{in}(1+\beta A)$) of a Voltage-Series feedback configuration. [PYQ: 2017, 2021, 2022, 2024] [Heavily Tested]
• Derive the expression for input impedance with feedback ($Z_{inF}=\frac{Z_{in}}{1+\beta A}$) of a Voltage-Shunt feedback configuration. [PYQ: 2017]
• Derive the expression for output impedance with feedback ($Z_{outF}=\frac{Z_{out}}{1+\beta A}$) of a Voltage-Series feedback configuration. [PYQ: 2018, 2021]
• Derive the expression for output impedance with feedback ($Z_{outF}=Z_{out}(1+\beta A)$) of a Current-Series feedback configuration. [PYQ: 2018, 2019, 2021, 2023] [Heavily Tested]
• Derive the mathematical expression showing that the bandwidth of an amplifier is increased by negative feedback ($B{W}_F=BW(1+\beta A)$).
• Derive the mathematical expression showing that negative feedback reduces harmonic distortion ($D_F=\frac{D}{1+\beta A}$).

Proofs

• Prove that the gain of an amplifier with negative feedback is more stable than the gain without feedback. [PYQ: 2019]
• Prove that the gain stability of an amplifier with feedback is $\beta A$ times higher than that of the amplifier without feedback (fractional change in closed-loop gain is desensitized by a factor of $1+\beta A$). [PYQ: 2021, 2023, 2025] [Heavily Tested]
• Prove that the gain of a practical feedback amplifier is inversely proportional to the feedback factor ($\beta$) when loop gain is very large ($\beta A\gg 1$). [PYQ: 2015, 2016, 2018, 2020] [Heavily Tested]
• Prove that the total harmonic distortion of a feedback amplifier is lower than that of an amplifier without feedback by a factor of $1+\beta A$. [PYQ: 2016, 2017]

Comparison/Difference Tables

• Classify the four different feedback connection types and compare their properties (gain, bandwidth, input impedance, output impedance) in a comprehensive summary table. [PYQ: 2019, 2022, 2024] [Heavily Tested]
• Compare the characteristics and applications of positive feedback vs. negative feedback.

Diagrams & Circuits

• Draw the block diagram representation of a generalized feedback amplifier showing the mixer (subtractor), basic amplifier, sampling network, and feedback network. [PYQ: 2017]
• Draw the block diagrams of the four types of feedback configurations: Voltage-Series, Voltage-Shunt, Current-Series, and Current-Shunt configurations.
• Draw the circuit diagram of a FET amplifier utilizing negative feedback. [PYQ: 2018, 2021, 2023] [Heavily Tested]

Numericals & Calculations

• Solve for the fraction of output fed back to the input ($\beta$) given: overall gain of a multistage amplifier without feedback $A=140$, and with negative voltage feedback $A_F=17.5$. [PYQ: 2015, 2021]
• Solve for (i) voltage gain with feedback $A_F$ and (ii) value of feedback fraction $\beta$, given an open-loop gain $A=100,000$ and a negative feedback of $10\text{ dB}$. [PYQ: 2015, 2016, 2019] [Heavily Tested]
• Solve for the minimum voltage gain required and the feedback factor ($\beta$) to design an amplifier with a closed-loop voltage gain of $100$ which does not vary by more than $1\%$ when the basic amplifier gain varies by $20\%$. [PYQ: 2016, 2020]
• Solve for the minimum value of load resistance so that the voltage gain of an amplifier is not more than $67\text{ dB}$ given: open-circuit voltage gain of $70\text{ dB}$ and output resistance of $1.5\text{ k}\Omega$. [PYQ: 2017]
• Solve for the voltage gain without and with feedback for the FET amplifier circuit shown in Fig. 4(d) given parameters: $R_1=80\text{ k}\Omega$, $R_2=20\text{ k}\Omega$, $R_o=10\text{ k}\Omega$, $R_D=10\text{ k}\Omega$, and transconductance $g_m=4000\mu \text{S}$. [PYQ: 2018, 2021, 2023] [Heavily Tested]
• Solve for the percentage reduction in stage gain (i) without feedback and (ii) with negative feedback, given an amplifier without feedback has gain $A=50$ which falls to $A_F=25$ with negative voltage feedback, and then due to aging the basic amplifier gain falls to $40$. [PYQ: 2022]
• Solve for the percentage change in the gain of the feedback system if the open-loop gain $A_v$ falls by $6\text{ dB}$ due to aging, given feedback fraction $m_v=0.1$ and initial gain $A_v=100$. [PYQ: 2023, 2024, 2025] [Heavily Tested]

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Chapter 3: Oscillators

Definitions & Core Terminology

• Define an electronic Oscillator. [PYQ: 2015, 2016, 2022]
• Define a “Sinusoidal Oscillator” and state its difference from non-sinusoidal oscillators. [PYQ: 2019, 2020, 2023, 2024] [Heavily Tested]
• State the Barkhausen Criterion for sustained self-oscillations. [PYQ: 2016, 2017]
• Define “Piezoelectric Crystal” and the “Piezoelectric effect.” [PYQ: 2015]
• Define the “intrinsic stand-off ratio” ($\eta$) of a Unijunction Transistor (UJT).
• Define the “frequency stability” of an oscillator.
• Define “negative resistance” as used in negative resistance oscillators.

Core Principles & Explanations

• Explain the principle of operation of a parallel LC resonant tank circuit for generating oscillations. [PYQ: 2015]
• Explain how a transistor acts as an oscillator.
• State and explain the conditions necessary to sustain undamped oscillations in a tank circuit. [PYQ: 2016, 2018, 2021, 2022, 2024, 2025] [Heavily Tested]
• State the requirements necessary to work a transistor as an oscillator. [PYQ: 2015, 2018, 2019, 2020, 2023, 2024] [Heavily Tested]
• Explain the usage/applications of an oscillator and why it is preferred as a frequency generator. [PYQ: 2021, 2022, 2025]
• Describe the functions of the main components required for designing an oscillator. [PYQ: 2021, 2023, 2024] [Heavily Tested]
• State and explain the essential parts of a transistor oscillator (tank circuit, amplifier, feedback circuit). [PYQ: 2022]
• Explain the graphical/phasor explanation of the Barkhausen Criterion. [PYQ: 2018]
• Explain the operation of a Tuned Collector Oscillator. [PYQ: 2019]
• Explain the operation of a Hartley Oscillator. [PYQ: 2017, 2022]
• Explain the operation of a Colpitts Oscillator. [PYQ: 2018, 2023, 2025] [Heavily Tested]
• Explain the principle of phase shift circuit in an RC Phase-Shift Oscillator. [PYQ: 2016, 2017, 2018, 2024] [Heavily Tested]
• Explain the operation of a Wien Bridge Oscillator and the specific function of the tungsten lamp in stabilizing output amplitude. [PYQ: 2015, 2019, 2024, 2025] [Heavily Tested]
• Explain the limitations of LC and RC oscillators that make crystal oscillators preferred. [PYQ: 2016, 2017, 2021, 2025] [Heavily Tested]
• Explain the electrical equivalent circuit of a quartz crystal.
• Explain the frequency response of a quartz crystal for parallel and series resonance conditions. [PYQ: 2016, 2017, 2019, 2021, 2025] [Heavily Tested]
• Explain the operation of a UJT Relaxation Oscillator. [PYQ: 2017, 2022, 2025] [Heavily Tested]

Derivations

• Derive the equation for feedback fraction ($\beta =\frac{C_1}{C_2}$) and the operating frequency ($f=\frac{1}{2\pi \sqrt{L{C}_T}}$) of a Colpitts Oscillator.
• Derive the equation for feedback fraction ($\beta =\frac{L_2}{L_1}$) and the operating frequency ($f=\frac{1}{2\pi \sqrt{L_{T}C}}$) of a Hartley Oscillator.
• Derive the expression for the frequency of oscillation ($f=\frac{1}{2\pi RC\sqrt{6}}$) and the required voltage gain ($A_v\ge 29$) for a 3-stage BJT Phase-Shift Oscillator.
• Derive the expression for the frequency of oscillation ($f=\frac{1}{2\pi RC}$) for a Wien Bridge Oscillator.
• Derive the equations for the series resonant frequency ($f_s=\frac{1}{2\pi \sqrt{LC}}$) and the parallel resonant frequency ($f_p=\frac{1}{2\pi \sqrt{L{C}_T}}$ where $C_T=\frac{C{C}_m}{C+C_m}$) of a crystal.
• Derive the equation for the frequency of the generated sawtooth output of a UJT Relaxation Oscillator ($f=\frac{1}{RC\ln (1/(1-\eta ))}$). [PYQ: 2022, 2025]

Proofs

• Prove using loop phase shift that an RC phase shift network requires exactly 3 RC stages of $60^{\circ }$ each to achieve the necessary $180^{\circ }$ phase shift in the feedback loop.

Comparison/Difference Tables

• Compare Colpitts and Hartley Oscillators in terms of tank circuit components, feedback method, and frequency range. [PYQ: 2020]
• Differentiate between RC oscillators (low frequency) and LC oscillators (high frequency).
• List the advantages and disadvantages of Wien Bridge Oscillators. [PYQ: 2015, 2019, 2024] [Heavily Tested]

Diagrams & Circuits

• Draw the circuit diagram of a Tuned Collector Oscillator. [PYQ: 2019]
• Draw the circuit diagram of a Hartley Oscillator. [PYQ: 2017, 2022]
• Draw the circuit diagram of a Colpitts Oscillator. [PYQ: 2015, 2018, 2019, 2022, 2023, 2024, 2025] [Heavily Tested]
• Draw the circuit diagram of a 3-stage BJT RC Phase-Shift Oscillator.
• Draw the circuit diagram of a Wien Bridge Oscillator using BJT/Op-Amp. [PYQ: 2015, 2016, 2019, 2024] [Heavily Tested]
• Draw the electrical equivalent circuit of a quartz crystal.
• Plot the reactance vs. frequency graph of a quartz crystal showing series resonance frequency ($f_s$) and parallel resonance frequency ($f_p$). [PYQ: 2016, 2017, 2019, 2021, 2025] [Heavily Tested]
• Draw the circuit diagram of a transistor-based Crystal Oscillator.
• Draw the schematic and output sawtooth waveform of a UJT Relaxation Oscillator. [PYQ: 2017, 2022, 2025] [Heavily Tested]

Numericals & Calculations

• Solve for (i) operating frequency ($f_0$) and (ii) feedback fraction ($m_v$) of the Colpitts Oscillator shown in Fig. 2(d) / Figure 3(c) given parameters: $R_1,R_2,R_E,C_E$, RFC choke, $C_1=0.001\mu \text{F}$, $C_2=0.01\mu \text{F}$, and $L=15\mu \text{H}$. [PYQ: 2015, 2019, 2022, 2024] [Heavily Tested]
• Determine the frequency of oscillation, feedback fraction, and minimum voltage gain needed to start oscillation for the oscillator circuit shown in Fig. 2(d). [PYQ: 2017]
• Solve for the frequency of oscillation of the Wien Bridge Oscillator shown in Fig. 2(d) / Fig. 2(d) given: $R_1=R_2=220\text{ k}\Omega$ and $C_1=C_2=250\text{ pF}$. [PYQ: 2016]
• Solve for Colpitts Oscillator capacitor values ($C_1,C_2$) given $f_r=1\text{ MHz}$, feedback fraction $m_v=0.25$, and inductor value $L$ equal to (last two digits of your Roll/4) mH. [PYQ: 2020]
• Solve for Colpitts Oscillator capacitor values ($C_1,C_2$) given $f=1\text{ MHz}$, feedback fraction $m_v=0.25$, and inductor value $L=1\text{ mH}$. [PYQ: 2025]
• Solve for Hartley Oscillator inductor values ($L_1,L_2$) given operating frequency $f=1\text{ MHz}$, feedback fraction $m_v=0.2$, and capacitor value $C=1\text{ pF}$. [PYQ: 2023]
• Solve for the series resonant frequency ($f_s$) and parallel resonant frequency ($f_p$) of a crystal whose equivalent ac circuit parameters are: $L=1\text{ H}$, $C=0.001\text{ pF}$, $R=1000\Omega$, and $C_m=20\text{ pF}$. [PYQ: 2017, 2018, 2022, 2024] [Heavily Tested]
• Solve for the series resonant frequency ($f_s$) and parallel resonant frequency ($f_p$) of a crystal whose equivalent ac circuit parameters are: $L=1\text{ H}$, $C=0.001\text{ pF}$, $R=100\Omega$ and $C_m=20\text{ pF}$. [PYQ: 2025]
• Solve for series resonant frequency ($f_s$) and parallel resonant frequency ($f_p$) of a crystal whose equivalent parameters are: $L=2\text{ H}$, $C=0.01\text{ pF}$, $R=1000\Omega$, and $C_m=20\text{ pF}$. [PYQ: 2019]

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Sources Referenced:

• Syllabus: ECE 2101 Course Contents pg 1 (Tuned Amplifiers, Feedback Amplifiers, Oscillators)
• Class Notes: Department of ECE Slide Presentations (01 Tuned Amplifiers.pdf, 03 Feedback Amplifiers.pdf, 02 Oscillators.pdf) by Md. Khorshed Alom; handwritten lecture booklets (Aysha mam-2309008.pdf).
• Reference Books: V. K. Mehta & Rohit Mehta, Principles Of Electronics (Chapter 15: Tuned Amplifiers, Chapter 20: Sinusoidal Oscillators); Albert Malvino, Electronic Principles 9th Edition (Chapter 17: Negative Feedback, Chapter 21: Oscillators).
• Previous Year Questions (PYQs): Verbatim exam sheets of Khulna University of Engineering & Technology (KUET) from 2015 to 2025.

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Let me know when you are ready to tackle Instructor 2 (Diode Wave Shaping, Op-Amp Basics, Integrators/Differentiators, Schmitt Triggers, Active Filters, 555 Timers, and Phase Locked Loops)!