(SEM III) THEORY EXAMINATION 2020-21 ELECTRONIC DEVICES

This document is a B.Tech Semester III Theory Examination Question Paper for the subject Electronic Devices (Subject Code: KEC301) under Dr. A.P.J. Abdul Kalam Technical University (AKTU) for the academic session 2020–2021. The exam carries 100 marks and the duration is 3 hours. The question paper assesses a student's understanding of semiconductor physics, diodes, MOSFETs, transistor characteristics, breakdown mechanisms, optoelectronic devices, feedback concepts, and electronic device modeling.

The paper is divided into seven structured questions, organized across multiple sections, allowing students to attempt both short conceptual answers and long analytical/descriptive problems.

Section A – Short Conceptual Questions (10 × 2 = 20 Marks)

This section presents ten brief questions, each worth 2 marks. They test fundamental definitions and concepts such as diffusion, effective mass of carriers, avalanche breakdown, sheet resistance, base width modulation, and positive/negative feedback.
The page also includes questions on difference between direct and indirect semiconductors, MOSFET temperature behavior, and semiconductor materials suitable for luminescence.

Section B – Detailed Explanatory Questions (Any 3 × 10 Marks)

This section contains long descriptive questions on core electronic device topics:

PN junction diode working with V–I characteristics

N-channel MOSFET operation

Photodiode construction and operation

Transistor characteristics in CE configuration (active & cutoff modes)

Direct vs indirect bandgap semiconductors and energy band variation

These questions require diagrams, characteristics curves, and conceptual explanation.

Section C – Device Models & Optoelectronics (10 Marks)

Students choose one:

Small-signal models of a MOS transistor
or

Working and characteristics of LED and Solar Cell

Section D – Semiconductor Physics (10 Marks)

This section dives deeper into semiconductor theory:

Fermi level and the effect of temperature & doping on mobility
or

Derivation of continuity equation and diffusion length using drift and diffusion concepts

These are mathematical/derivational in nature.

Section E – MOSFET Biasing & Zener Diode (10 Marks)

Students must answer one:

MOSFET amplifier biasing circuit and its explanation
or

Working principle & V–I characteristics of a Zener diode

Both questions require diagrams.

Section F – PN Diode Equation & Fermi Level Numericals (10 Marks)

This section includes:

Derivation of diode current equation
or

Numerical problem involving phosphorus-doped silicon at 1000 K:

Fermi level position

Electron & hole concentration

This assesses conceptual + numerical understanding.

Section G – Schottky Diode & Ebers Moll Model (10 Marks)

The final long-answer section provides two options:

Detailed explanation of a Schottky diode and its applications
or

Ebers-Moll model of a transistor

Both require in-depth understanding of diode/transistor behavior.

Overall Description

This question paper is a comprehensive evaluation tool for the Electronic Devices course. It covers:

Semiconductor physics fundamentals

pn junction behavior

MOSFET working & models

BJT characteristics

Optoelectronic devices (LED, Solar cell, Photodiode)

Breakdown mechanisms

Zener diode

Fermi levels & carrier concentrations

Device modeling (Ebers-Moll, small signal models)

The paper is structured according to AKTU’s standard exam pattern, ensuring a balance of conceptual definitions, numerical analysis, device modeling, and theoretical descriptions.