About this previous year paper
This document contains the complete B.Tech Semester III – Theory Examination 2017–18 question paper for Electronic Devices and Circuits (REC-302). The paper consists of 2 printed pages, carries 70 marks, and evaluates a student’s conceptual and analytical understanding of semiconductor physics, electronic devices, amplifiers, MOSFET/BJT behavior, breakdown mechanisms, and oscillator theory.
Section A — Short Conceptual Questions (14 Marks)
Section A contains seven brief questions designed to test basic theoretical knowledge of electronic devices:
Advantages of negative feedback in amplifiers
Meaning of Base Width Modulation (Early Effect) in BJTs
Concept of fluorescence
Difference between direct and indirect recombination lifetimes
Overview of Avalanche breakdown
Difference between EMOSFET and DMOSFET
Calculation of current gain (β) in CE configuration for α = 0.98
These questions ensure students understand core semiconductor effects and fundamental device behavior.
Section B — Detailed Analytical & Numerical Questions (21 Marks)
Students must attempt any three out of five questions. This section includes derivations, explanations, and numerical calculations:
Drawing CE amplifier with emitter resistance & deriving performance parameters
Discussing internal capacitances of BJT and MOSFET
Explaining luminescence, types of luminescence, and difference between fluorescence & phosphorescence, including fluorescence lamp application
Deriving Einstein relation between diffusion coefficient and mobility
Numerical problem on abrupt junction formation, including:
Depletion region width
Penetration depth on p-side & n-side
Using parameters: donor concentration, acceptor concentration, intrinsic carrier concentration, permittivity, and temperature
This section requires deep theoretical understanding and application of semiconductor equations.
Section C — Advanced Device Modeling & Circuit Analysis (35 Marks)
Students must attempt one part from each group. These questions test high-level understanding and design ability:
1. Feedback & Amplifier Analysis
Drawing four basic feedback topologies and comparing input/output resistances
Working of Common Source (CS) amplifier with source resistance, small-signal model & voltage gain derivation
2. Semiconductor Physics
Difference between direct and indirect bandgap semiconductors & effect of alloy composition
Concept of Fermi level, impact of doping & temperature on mobility, and calculation of equilibrium hole concentration for doped silicon
3. MOSFET Design & Characteristics
Designing a MOSFET circuit to achieve specific drain voltage, and finding effective resistance
Construction and I–V characteristics of a P-channel EMOSFET
4. BJT Applications & Biasing
BJT as amplifier and switch with circuit diagrams, waveforms, and expressions
Various biasing techniques for BJTs, explaining any two in detail
5. High Frequency Models & Oscillators
High-frequency hybrid-π model of MOSFET, showing fT=gm2π(Cgs+Cgd)f_T = \frac{g_m}{2\pi(C_{gs}+C_{gd})}fT=2π(Cgs+Cgd)gm
Derivation of oscillation conditions and frequency expression for a phase-shift oscillator
Summary
This exam paper thoroughly assesses student understanding across:
Semiconductor physics
PN junction behavior
BJT & MOSFET parameters
Amplifier design and small-signal analysis
Feedback types & frequency response
Breakdown mechanisms & recombination
Oscillators and high-frequency modeling
It is a comprehensive academic resource for students studying electronic devices, circuits, and solid-state electronics.