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Electronic Devices and Circuits

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3rd-sem_Electronic Devices and Circuits.pdf

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Most Frequently Asked Questions

Top recurring IOE board exam questions for Electronic Devices 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