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.
