(SEM IV) THEORY EXAMINATION 2024-25 ANALOG CIRCUITS

This document contains the complete B.Tech Semester IV – Theory Examination 2024–25 question paper for Analog Circuits (BEC402). The paper spans three printed pages, carries 70 marks, and evaluates a student’s understanding of transistor models, amplifiers, feedback systems, oscillators, MOSFET behavior, differential amplifiers, current mirrors, and operational amplifier applications.
 

Section A – Short Conceptual Questions (14 Marks)

Section A includes seven 2-mark questions testing the basics of analog electronics. Topics include:

Transconductance & trans-resistance amplifiers

Drawing the T-model equivalent circuit of an NPN transistor (Page 1)

Explaining the Barkhausen Criterion for sustained oscillations

Principle of crystal oscillators

Terms related to current mirror circuits—minimum sustainable voltage & maximum usable load

Op-Amp parameters: slew rate & CMRR

Calculating gm and re for a BJT at 1 mA collector current

These questions test fundamental device-level and amplifier-level knowledge.
 

Section B – Medium-Level Analytical Questions (21 Marks)

Students must attempt any three of the five questions.

Topics include:

CE Amplifier – Hybrid-π Model

Drawing a single-stage CE amplifier and deriving expressions for ic, gm, ib.

Shunt-Series Feedback Amplifier (Design Problem)

Design of a shunt-series feedback amplifier with expressions for Af, Rof, Rif.

Wien Bridge Oscillator

Explaining operation and deriving feedback factor β and frequency of oscillation.

Differential Amplifier – Output Voltage

Numerical calculation of Vo of the differential amplifier diagram shown on Page 1.

Op-Amp Applications

Designing

Unity-gain amplifier

Integrator circuit

This section checks analysis and design capability.
 

Section C – Long, Advanced Questions (35 Marks)

Students must attempt one part from each Q3–Q7.

Q3 – Common Collector Amplifier / Multistage Amplification

Drawing single-stage CC (emitter follower) using T-model & deriving voltage gain

OR explaining low-frequency & high-frequency behavior of multistage amplifiers

Q4 – MOSFET High-Frequency Model / Series-Series Feedback

Drawing high-frequency MOSFET model & deriving fH

OR designing a series-series feedback amplifier

Q5 – RC-Phase Shift Oscillator / Hartley Oscillator

RC phase-shift oscillator using Op-Amp with conditions and frequency

OR deriving frequency of oscillation for Hartley oscillator
(Page 2)

Q6 – Differential Amplifier / Current in Transistor Network

Drawing differential amplifier structure & calculating differential gain, common-mode gain, CMRR

OR computing currents through Q2 and Q3 in the given transistor network (diagram on Page 2)

Q7 – Op-Amp Limitations / Op-Amp Numerical

Effect of finite loop gain and finite bandwidth on Op-Amp performance + definition of input offset voltage & current

OR evaluation of output voltage Vo for the circuit shown on Page 3

These questions test design thinking, system-level analysis, and theoretical derivations.
 

Summary

The Analog Circuits (BEC402) exam paper examines:

Transistor small-signal models (T-model, hybrid-π)

BJT & MOSFET amplifier analysis

Feedback amplifier design (shunt-series, series-series)

Frequency response & high-frequency behavior

Wien Bridge, Hartley, and RC phase-shift oscillators

Differential amplifiers & CMRR

Current mirror limitations and transistor biasing

Op-Amp concepts, applications & practical non-idealities

This paper serves as a complete academic resource for students learning analog device behavior and amplifier/oscillator design.