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ENEX 151Bachelor in Electronics, Communication and Information Engineering · Semester 21 Paper Available

Electronic Device and Circuits

Past examination question papers and complete curriculum syllabus for Electronic Device and Circuits (ENEX 151), Bachelor in Electronics, Communication and Information Engineering Semester 2 under Institute of Engineering (IOE), Tribhuvan University.

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2nd-sem_Electronic Device and Circuits.pdf

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Most Frequently Asked Questions

Top recurring IOE board exam questions for Electronic Device and Circuits with verified mark schemes, formula notation, and recurrence frequency.

Showing 30 of 30 top repeated questions

The Bipolar Junction Transistor (BJT)

4 Questions
#1Repeated 4 Times[8 Marks]The Bipolar Junction Transistor (BJT)
Draw the AC equivalent circuit of a Common Emitter (CE) BJT amplifier with a bypassed emitter resistor using the re-model. Derive mathematical expressions for input impedance $Z_{in}$, output impedance $Z_{out}$, voltage gain $A_v$, and current gain $A_i$.
Appeared in:2082 Baishakh2079 Bhadra2076 Chaitra2074 Ashwin
#2Repeated 2 Times[6 Marks]The Bipolar Junction Transistor (BJT)
Determine the input resistance, output resistance, and voltage gain of a Common Collector (Emitter Follower) BJT amplifier. Explain why it is used as a buffer amplifier.
Appeared in:2076 Chaitra2074 Ashwin
#3Repeated 2 Times[8 Marks]The Bipolar Junction Transistor (BJT)
Explain why common collector (CC) amplifier is called an emitter follower. Derive the expressions for input impedance $Z_i$, output impedance $Z_o$, and voltage gain $A_v$ of an emitter follower using hybrid-$\pi$ model.
Appeared in:2083 Baishakh2081 Bhadra
#4Repeated 2 Times[8 Marks]The Bipolar Junction Transistor (BJT)
Draw the circuit diagram of a single-stage CE amplifier with an emitter bypass capacitor $C_E$. Explain how $C_E$ and coupling capacitors affect the low-frequency response of the amplifier.
Appeared in:2082 Baishakh2080 Bhadra

Field-Effect Transistor

5 Questions
#1Repeated 4 Times[8 Marks]Field-Effect Transistor
Describe the physical construction and working principle of an N-channel Enhancement-type MOSFET (E-MOSFET) with neat drain and transfer characteristic curves. Define threshold voltage $V_{th}$ and transconductance $g_m$.
Appeared in:2082 Baishakh2079 Bhadra2076 Chaitra2074 Ashwin
#2Repeated 3 Times[6 Marks]Field-Effect Transistor
Explain the construction and operation of N-channel Depletion-type MOSFET (D-MOSFET). Derive the transconductance formula $g_m = \frac{2I_{DSS}}{|V_P|}\left(1 - \frac{V_{GS}}{V_P}\right)$ from Shockley's equation.
Appeared in:2079 Bhadra2076 Chaitra2074 Ashwin
#3Repeated 3 Times[6 Marks]Field-Effect Transistor
For a voltage-divider biased JFET circuit with $I_{DSS} = 10\text{ mA}$ and $V_P = -5\text{ V}$, calculate the quiescent operating point ($I_{DQ}$ and $V_{DSQ}$) and draw the DC load line.
Appeared in:2082 Baishakh2079 Bhadra2076 Chaitra
#4Repeated 2 Times[8 Marks]Field-Effect Transistor
Differentiate between JFET and MOSFET. Explain the drain and transfer characteristics of an N-channel Enhancement-type MOSFET (E-MOSFET) with neat diagrams and derive Shockley's/drain current equation in the saturation region.
Appeared in:2082 Shrawan2081 Bhadra
#5Repeated 2 Times[6 Marks]Field-Effect Transistor
Explain the working principle of a CMOS inverter. Draw its circuit diagram and voltage transfer characteristics (VTC) curve, explaining static power dissipation.
Appeared in:2082 Baishakh2079 Baishakh

Operational Amplifier Circuits and Oscillator

8 Questions
#1Repeated 4 Times[8 Marks]Operational Amplifier Circuits and Oscillator
State the Barkhausen criteria for sustained oscillations. Draw the circuit diagram of an RC Phase Shift Oscillator using BJT/Op-Amp and derive the expression for the frequency of oscillation $f_0 = \frac{1}{2\pi R C \sqrt{6}}$ and required amplifier gain.
Appeared in:2081 Bhadra2079 Bhadra2076 Chaitra2074 Ashwin
#2Repeated 3 Times[6 Marks]Operational Amplifier Circuits and Oscillator
Draw the circuit diagram of an Op-Amp Wien Bridge Oscillator. Derive the expression for frequency of oscillation $f_0 = \frac{1}{2\pi RC}$ and the condition on resistor ratio for sustained oscillations ($A_v \ge 3$).
Appeared in:2079 Bhadra2076 Chaitra2074 Ashwin
#3Repeated 3 Times[8 Marks]Operational Amplifier Circuits and Oscillator
Explain the internal block diagram and operation of an Astable Multivibrator using IC 555 timer. Sketch capacitor and output voltage waveforms, and derive expressions for charging time $T_{high}$, discharging time $T_{low}$, frequency, and duty cycle.
Appeared in:2082 Baishakh2076 Chaitra2074 Ashwin
#4Repeated 2 Times[6 Marks]Operational Amplifier Circuits and Oscillator
Draw the circuit diagram of a Colpitts (or Hartley) LC oscillator and derive the expression for its resonant frequency of oscillation.
Appeared in:2076 Chaitra2074 Ashwin
#5Repeated 2 Times[8 Marks]Operational Amplifier Circuits and Oscillator
Explain the four basic feedback topologies: Voltage-Series, Voltage-Shunt, Current-Series, and Current-Shunt. How does negative feedback affect gain stability, input impedance, output impedance, and bandwidth?
Appeared in:2082 Shrawan2081 Bhadra
#6Repeated 2 Times[8 Marks]Operational Amplifier Circuits and Oscillator
Explain the working principle of a Hartley oscillator and a Colpitts oscillator. Draw their circuit diagrams and derive the expression for the frequency of oscillation.
Appeared in:2082 Baishakh2079 Bhadra
#7Repeated 2 Times[8 Marks]Operational Amplifier Circuits and Oscillator
Draw the internal block diagram of IC 555 Timer. Explain the operation of IC 555 configured as an Astable Multivibrator and derive the expressions for charging time $t_{\text{high}}$, discharging time $t_{\text{low}}$, and duty cycle.
Appeared in:2082 Shrawan2081 Bhadra
#8Repeated 2 Times[6 Marks]Operational Amplifier Circuits and Oscillator
Explain the operation of a Monostable Multivibrator using IC 555 timer. Derive the expression for the pulse width $W = 1.1 R C$ and draw relevant capacitor voltage and output voltage waveforms.
Appeared in:2082 Baishakh2078 Bhadra

Output Stages and Power Amplifiers

5 Questions
#1Repeated 4 Times[8 Marks]Output Stages and Power Amplifiers
Draw the circuit diagram of a transformer-coupled Class B push-pull power amplifier. Derive the expression for its maximum theoretical conversion efficiency ($\\eta = 78.5\\%$) and maximum transistor power dissipation.
Appeared in:2081 Bhadra2079 Bhadra2076 Chaitra2074 Ashwin
#2Repeated 4 Times[6 Marks]Output Stages and Power Amplifiers
What is crossover distortion in a Class B amplifier? Draw the circuit diagram of a complementary-symmetry (or quasi-complementary) Class AB amplifier and explain how diode bias eliminates crossover distortion.
Appeared in:2081 Bhadra2079 Bhadra2076 Chaitra2074 Ashwin
#3Repeated 4 Times[8 Marks]Output Stages and Power Amplifiers
When are tuned amplifiers used? Draw the circuit diagram of a single-tuned Class A amplifier and derive the expression for its resonant frequency, quality factor ($Q$), and 3dB bandwidth.
Appeared in:2082 Baishakh2079 Bhadra2076 Chaitra2074 Ashwin
#4Repeated 2 Times[6 Marks]Output Stages and Power Amplifiers
Draw the circuit diagram of a series-fed Class A power amplifier and derive the expression for its maximum theoretical collector conversion efficiency ($\eta_{\max} = 25\%$).
Appeared in:2083 Baishakh2081 Bhadra
#5Repeated 2 Times[6 Marks]Output Stages and Power Amplifiers
Draw the circuit diagram of a single-tuned capacitive coupled Class A amplifier and determine the range of frequencies in which it gives maximum gain within the 3 dB bandwidth.
Appeared in:2083 Baishakh2080 Baishakh

Power Supplies, Breakdown Diodes, and Voltage Reference

8 Questions
#1Repeated 4 Times[8 Marks]Power Supplies, Breakdown Diodes, and Voltage Reference
Draw a standard series DC voltage regulator circuit using BJT and Zener diode. Derive its voltage stability factor ($S_V = \frac{\Delta V_o}{\Delta V_{in}}$) and explain the operation of short-circuit current limiting protection.
Appeared in:2082 Baishakh2079 Bhadra2076 Chaitra2074 Ashwin
#2Repeated 3 Times[6 Marks]Power Supplies, Breakdown Diodes, and Voltage Reference
Design a variable DC voltage regulator circuit providing an output from $5\text{ V}$ to $20\text{ V}$ using the three-terminal adjustable voltage regulator IC LM317. Show all resistor calculations.
Appeared in:2082 Baishakh2076 Chaitra2074 Ashwin
#3Repeated 3 Times[4 Marks]Power Supplies, Breakdown Diodes, and Voltage Reference
Derive the mathematical expression for dynamic (AC) resistance of a PN junction diode. If a diode conducts $1\text{ mA}$ at $20^\circ\text{C}$, determine its dynamic resistance at forward bias.
Appeared in:2082 Baishakh2076 Chaitra2074 Ashwin
#4Repeated 2 Times[6 Marks]Power Supplies, Breakdown Diodes, and Voltage Reference
Explain the operation of an Op-Amp based Precision Half-Wave Rectifier with circuit diagram and transfer characteristics. Why is it preferred over ordinary diode rectifiers for small signals?
Appeared in:2079 Bhadra2076 Chaitra
#5Repeated 2 Times[6 Marks]Power Supplies, Breakdown Diodes, and Voltage Reference
Explain different large-signal and small-signal models of a PN junction diode. Derive the expression for dynamic resistance $r_d$ and explain diffusion capacitance vs transition capacitance.
Appeared in:2083 Baishakh2082 Baishakh
#6Repeated 2 Times[8 Marks]Power Supplies, Breakdown Diodes, and Voltage Reference
Explain the operation of a series pass transistor voltage regulator with error amplifier and current limiting protection circuit.
Appeared in:2083 Baishakh2082 Shrawan
#7Repeated 2 Times[8 Marks]Power Supplies, Breakdown Diodes, and Voltage Reference
Draw the circuit diagram of an Op-Amp based Schmitt trigger. Explain its operation and derive expressions for Upper Threshold Voltage ($V_{UT}$) and Lower Threshold Voltage ($V_{LT}$).
Appeared in:2082 Baishakh2080 Bhadra
#8Repeated 2 Times[6 Marks]Power Supplies, Breakdown Diodes, and Voltage Reference
Explain the operation of an Op-Amp based precision half-wave rectifier and precision full-wave rectifier, explaining why ordinary diodes cannot rectify millivolt signals.
Appeared in:2083 Baishakh2081 Bhadra

Curriculum Syllabus & Course Topics

Sourced from TU curriculum portal
Full Syllabus (PDF)
Chapter-wise Units & Micro-Syllabus Topics (5 Units)

  1. 1. The Bipolar Junction Transistor (BJT)

    • 1.1Review of operation of the npn transistor in the active mode
    • 1.2Review of graphical representation of transistor characteristics
    • 1.3Analysis of transistor circuits at DC
    • 1.4Graphical DC load line analysis
    • 1.5Transistor as an amplifier ( r , r g )  e, m
    • 1.6Biasing BJT for discrete-circuit design
    • 1.7Small signal equivalent circuit models ( and T)
    • 1.8Basic single-stage BJT amplifier configuration (C-B, C-E, C-C)
    • 1.9Small signal analysis of amplifier
    • 1.10Transistor as a switch – cutoff and saturation
    • 1.11A general large-signal model of the BJT: The Ebers-Moll model

  2. 2. Field-Effect Transistor

    • 2.1Structure and physical operation of the junction field-effect transistor
    • 2.2Structure and physical operation of enhancement-type MOSFET
    • 2.3Current-voltage characteristic of enhancement-type MOSFET
    • 2.4The depletion-type MOSFET
    • 2.5Biasing in MOS amplifier circuits
    • 2.6MOSFET circuits at DC
    • 2.7MOSFET as an amplifier (Common source)
    • 2.8MOSFET and CMOS as logic circuits

  3. 3. Operational Amplifier Circuits and Oscillator

    • 3.1Review of basic principles of sinusoidal oscillator
    • 3.2Review of Op-Amp square and triangular, RC oscillator circuits
    • 3.3LC and crystal oscillators
    • 3.4Integrated circuit timers
    • 3.5Precision rectifier circuits
    • 3.6Bias circuits suitable for IC design
    • 3.7The Widlar current source
    • 3.8The differential amplifier
    • 3.9Active loads
    • 3.10Output stages

  4. 4. Output Stages and Power Amplifiers

    • 4.1Classification of output stages
    • 4.2Class A output stage
    • 4.3Class B output stage
    • 4.4Class AB output stage
    • 4.5Biasing of class AB output stage
    • 4.6Power BJT’s
    • 4.7Transformer-coupled push-pull stage
    • 4.8Tuned amplifiers

  5. 5. Power Supplies, Breakdown Diodes, and Voltage Reference

    • 5.1Unregulated power supply
    • 5.2Zener regulated power supply
    • 5.3Zener diodes, bandgap voltage reference, constant current diodes
    • 5.4Transistor shunt/series voltage regulator
    • 5.5Improving voltage regulator performance with feedback
    • 5.6IC voltage regulator

Examination Scheme & Marks Distribution

Evaluation Structure

  • Final Board Theory Exam: 60 Marks (Pass mark: 24)
  • Internal Assessment: 40 Marks (Pass mark: 16)
  • Practical / Lab Exam: 25 or 50 Marks (Continuous lab evaluation + viva, where applicable)

* This is the general current IOE 60/40 scheme; verify course-specific details in the syllabus above.

Exam Preparation Guidelines

  • Review the available past examination paper to understand question styling, typical derivation topics, and marks allocation.
  • Practice drawing labeled circuit schematics, deriving transfer functions, and showing systematic mathematical steps.
  • Structure answers with labeled diagrams, concise bullet points, and highlight final answers in numerical solutions.

Frequently Asked Questions (Electronic Device and Circuits)

Q: How can I download Electronic Device and Circuits past question papers?

You can preview or download the Electronic Device and Circuits question papers (PDF) directly using the built-in viewer on this page with zero redirects or paywalls.

Q: What is the pass mark for Electronic Device and Circuits?

The general current scheme is a 60-mark final theory exam and a 40-mark internal assessment, with pass marks of 24 and 16. Verify the course-specific syllabus above.

Q: Where can I find the complete syllabus for this subject?

The available chapter-wise syllabus and topic breakdown is indexed in the Syllabus section above, with links to the curriculum PDF source.

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