RGPV • B.Tech IV Semester • EC-405

EC-405 Analog Circuits

Previous Year Questions • PYQ Analysis • Most Repeated Questions • Important Topics • Exam Preparation

5 PYQ Papers Analysed
5/5 Highest Repetition
20 Top Questions
70 Maximum Marks

EC-405 PYQ Intelligence

Analysis of June 2022 → June 2025 papers

🔥 What This Page Contains

The questions have been grouped by concept rather than exact wording. Therefore, if RGPV asks the same concept in a different form, it is counted as a repeated topic.


Highest repetition: Negative Feedback, Differential Amplifier and OP-AMP Offset Parameters.

📚 PYQ Papers Analysed

Five EC-405 GS papers used for the analysis

June 2022

EC-405 (GS)

Analysed

June 2023

EC-405 (GS)

Analysed

Nov 2023

EC-405 (GS)

Analysed

Dec 2024

EC-405 (GS)

Analysed

June 2025

EC-405 (GS)

Latest

🔥 Most Repeated Questions

Ranked according to repetition across the five supplied papers

Rank Question / Topic Frequency Priority
1 Negative Feedback in Amplifiers 5/5 🔥🔥🔥🔥🔥
1 Differential Amplifier 5/5 🔥🔥🔥🔥🔥
1 Input Offset Voltage / Offset Current / Bias Current 5/5 🔥🔥🔥🔥🔥
2 Feedback Topologies 4/5 🔥🔥🔥🔥
2 Fixed & Adjustable Voltage Regulators 4/5 🔥🔥🔥🔥
2 IC Datasheet / Information in Datasheets 4/5 🔥🔥🔥🔥
3 Barkhausen Criterion 3/5 🔥🔥🔥
3 RC Phase-Shift Oscillator 3/5 🔥🔥🔥
3 CMRR 3/5 🔥🔥🔥
3 OP-AMP Integrator 3/5 🔥🔥🔥
3 Butterworth Low-Pass Filter 3/5 🔥🔥🔥
3 555 Astable Multivibrator 3/5 🔥🔥🔥

🏆 Top 20 Important Questions

Prepare these questions first

5/5 • MUST PREPARE

1. Negative Feedback

Explain negative feedback in amplifiers. Discuss its advantages and disadvantages. Explain its effect on gain, bandwidth and distortion.

5/5 • MUST PREPARE

2. Differential Amplifier

Explain the construction and operation of a differential amplifier with a neat circuit diagram. Discuss its advantages and applications.

5/5 • MUST PREPARE

3. OP-AMP Offset Parameters

Explain input offset voltage, input offset current and input bias current. Discuss their effect on amplifier accuracy.

4/5 • HIGH PRIORITY

4. Feedback Topologies

Explain Voltage-Series, Voltage-Shunt, Current-Series and Current-Shunt feedback configurations.

4/5 • HIGH PRIORITY

5. Fixed & Adjustable Regulators

Explain the operation of fixed and adjustable voltage regulators. Compare their advantages and limitations.

4/5 • HIGH PRIORITY

6. IC Datasheet

What is a datasheet? Explain its importance and the information generally provided in an IC datasheet.

3/5

7. Barkhausen Criterion

Define Barkhausen criterion and explain its importance for sustained oscillations.

3/5

8. RC Phase-Shift Oscillator

Draw and explain the RC phase-shift oscillator and derive the frequency of oscillation.

3/5

9. CMRR

Define CMRR and explain its significance in a differential amplifier.

3/5

10. OP-AMP Integrator

Explain the operation of an OP-AMP integrator with a neat circuit diagram and derive its output equation.

3/5

11. Butterworth LPF

Design and explain a first-order or second-order Butterworth low-pass filter and obtain its frequency response.

3/5

12. 555 Astable Multivibrator

Draw the astable multivibrator circuit using IC-555 and explain its operation.

HIGH

13. Ideal OP-AMP Characteristics

Write and explain the essential ideal characteristics of an OP-AMP.

HIGH

14. Ideal vs Practical OP-AMP

Compare the characteristics of an ideal OP-AMP with a practical OP-AMP.

HIGH

15. Wien Bridge Oscillator

Explain the working principle of Wien Bridge oscillator with circuit diagram. Discuss advantages and limitations.

HIGH

16. Schmitt Trigger

Explain Schmitt Trigger with suitable circuit diagram and working.

HIGH

17. Zero Crossing Detector

Explain the operation of a Zero Crossing Detector using OP-AMP.

HIGH

18. LM317

Explain the features, specifications and applications of LM317 adjustable voltage regulator.

HIGH

19. Instrumentation Amplifier

Draw and explain the operation of an instrumentation amplifier and derive the required expression.

HIGH

20. Slew Rate & PSRR

Define and explain important OP-AMP parameters such as slew rate, PSRR and their effect on performance.

📖 Unit-Wise PYQ Priority

Focus on repeated concepts first

UNIT 1 — Feedback & Oscillators

+
  • Negative Feedback — ⭐⭐⭐⭐⭐
  • Feedback Topologies — ⭐⭐⭐⭐
  • Barkhausen Criterion — ⭐⭐⭐
  • RC Phase-Shift Oscillator — ⭐⭐⭐
  • Wien Bridge Oscillator — ⭐⭐⭐
  • Hartley Oscillator
  • Colpitts Oscillator
  • Crystal Oscillator

UNIT 2 — IC & Differential Amplifier

+
  • Differential Amplifier — ⭐⭐⭐⭐⭐
  • Single Input Unbalanced Output — ⭐⭐⭐⭐⭐
  • Single Input Balanced Output — ⭐⭐⭐⭐⭐
  • Dual Input Unbalanced Output — ⭐⭐⭐⭐
  • Input Offset Voltage — ⭐⭐⭐⭐⭐
  • Input Offset Current — ⭐⭐⭐⭐⭐
  • Input Bias Current — ⭐⭐⭐⭐⭐
  • CMRR — ⭐⭐⭐
  • IC characteristics
  • IC building components
  • Datasheets

UNIT 3 — OP-AMP Applications

+
  • OP-AMP Integrator — ⭐⭐⭐
  • Differentiator — ⭐⭐⭐
  • Instrumentation Amplifier — ⭐⭐⭐
  • Voltage-Series Feedback Amplifier
  • Voltage-Shunt Feedback Amplifier
  • Zero Crossing Detector
  • Slew Rate
  • PSRR
  • Comparator
  • AVC using OP-AMP

UNIT 4 — Filters & IC-555

+
  • Butterworth Low Pass Filter — ⭐⭐⭐
  • 555 Astable Multivibrator — ⭐⭐⭐
  • Schmitt Trigger — ⭐⭐⭐
  • Magnitude & Frequency Response
  • 555 Monostable Multivibrator
  • Peak Detector
  • Sample & Hold Circuit
  • Wien Bridge Oscillator

UNIT 5 — Wave Shaping & Voltage Regulators

+
  • Fixed Voltage Regulator — ⭐⭐⭐⭐
  • Adjustable Voltage Regulator — ⭐⭐⭐⭐
  • LM317 — ⭐⭐⭐
  • Standard Regulator IC Characteristics — ⭐⭐⭐
  • Switching Regulator — ⭐⭐⭐
  • Dual Power Supply — ⭐⭐⭐
  • Low-Dropout Regulator
  • Linear Regulator

📝 Important Questions From PYQs

Selected questions appearing in the supplied papers

June 2025 — EC-405 (GS)

Maximum Marks: 70

  1. Working principle and advantages/limitations of Wien Bridge Oscillator.
  2. Barkhausen criterion and its importance.
  3. Importance of IC datasheets and information provided.
  4. Single-input balanced-output differential amplifier.
  5. Differential amplifier numerical.
  6. Input offset voltage, offset current and input bias current.
  7. Voltage-series feedback amplifier.
  8. Magnitude and frequency response of filters.
  9. 555 timer block diagram and pin configuration.
  10. Peak detector circuit.
  11. Fixed and adjustable voltage regulators.
  12. LM317 features, specifications and applications.

December 2024 — EC-405 (GS)

Maximum Marks: 70

  1. Concept of feedback and negative feedback.
  2. Feedback topologies.
  3. Positive feedback and Barkhausen criterion.
  4. RC phase-shift oscillator.
  5. IC characteristics and advantages.
  6. Data sheets.
  7. Differential amplifier.
  8. Ideal OP-AMP equivalent circuit and IC-741 pins.
  9. CMRR, Slew Rate and PSRR.
  10. OP-AMP integrator and differentiator.
  11. Butterworth first-order low-pass filter.
  12. 555 astable multivibrator.
  13. Schmitt Trigger.
  14. Fixed and Adjustable Voltage Regulator.
  15. Switching Regulator.
  16. Dual Power Supply.

November 2023 — EC-405 (GS)

Maximum Marks: 70

  1. Negative feedback — advantages and disadvantages.
  2. Concept of feedback and types.
  3. RC phase-shift oscillator.
  4. Fixed and adjustable voltage regulators.
  5. Dual input unbalanced-output differential amplifier.
  6. Input bias current, input offset current and input offset voltage.
  7. Instrumentation amplifier.
  8. Characteristics of standard regulator ICs.
  9. Schmitt Trigger using 555 timer.
  10. 555 astable multivibrator.
  11. Clipper and clamper circuits.
  12. Zero Crossing Detector.
  13. CMRR.
  14. Wien Bridge Oscillator.

June 2023 — EC-405 (GS)

Maximum Marks: 70

  1. Negative feedback and its advantages.
  2. Effect of negative feedback on gain, bandwidth and distortion.
  3. Wien Bridge Oscillator.
  4. LC type oscillators.
  5. IC characteristics and data sheets.
  6. Single-input unbalanced-output differential amplifier.
  7. Standard regulator IC characteristics.
  8. Ideal vs practical OP-AMP.
  9. CMRR, Slew Rate and Offset Voltage.
  10. OP-AMP integrator and differentiator.
  11. Monostable Multivibrator using 555 timer.
  12. Sample and Hold circuit.
  13. Log/Antilog amplifier.
  14. Schmitt Trigger.
  15. Crystal Oscillator.
  16. AVC using OP-AMP.

June 2022 — EC-405 (GS)

Maximum Marks: 70

  1. Positive and negative feedback with Barkhausen criterion.
  2. Feedback circuit numerical.
  3. Integrated circuit advantages.
  4. Hartley oscillator.
  5. Input offset voltage, offset current, input bias current and output offset voltage.
  6. Butterworth second-order low-pass filter.
  7. Fixed and adjustable voltage regulators.
  8. Common-mode voltage of differential amplifier.
  9. Monostable, Bistable and Astable multivibrators.
  10. Zero Crossing Detector.
  11. OP-AMP integrator.
  12. Voltage-shunt feedback amplifier.
  13. VCO.
  14. Slew rate.
  15. Dual-input balanced-output differential amplifier.

🎯 Exam Preparation Priority

Use this order if your preparation time is limited

🔴 Tier 1 — Must Do

  • Negative Feedback
  • Differential Amplifier
  • OP-AMP Offset Parameters
  • Feedback Topologies
  • Fixed & Adjustable Regulators
  • Datasheet
  • CMRR

🟠 Tier 2 — High Priority

  • Barkhausen Criterion
  • RC Phase Shift Oscillator
  • Wien Bridge Oscillator
  • Ideal OP-AMP
  • OP-AMP Integrator
  • Butterworth LPF
  • 555 Astable

🔵 Tier 3 — Prepare Next

  • Schmitt Trigger
  • Zero Crossing Detector
  • Instrumentation Amplifier
  • LM317
  • Sample & Hold
  • Peak Detector
  • Switching Regulator

🏆 EC-405 Smart Preparation

First complete the 5/5 repeated topics, then the 4/5 topics, and finally cover the 3/5 topics. Do not study only exact question wording — prepare the complete concept because RGPV frequently changes the wording/configuration of the same topic.