BEEE-UNIT_2[1]

Overview of Electronics

  • Unit Topics:

    • Semiconductors, Diodes, and Transistors

    • Junction Field Effect Transistor (JFET) and Metal Oxide Semiconductor Field Effect Transistor (MOSFET)

    • Power Devices: SCR, BJT, MOSFET, IGBT

    • Switching Characteristics and Types of Power Converters

    • Linear Voltage Regulator and SMPS

    • Logic Expression Realization and Combinational Logic Design

    • Karnaugh Map (K-Map) Representation

    • FPGA Introduction

    • Practical applications: PCB Design, Soldering, Testing

Overview of Semiconductors

  • Material Classifications:

    • Conductors: Good conductors of electricity.

    • Insulators: Poor conductors of electricity.

    • Semiconductors: Conductivity lies between conductors and insulators.

  • Energy Band Structure of Semiconductors:

    • Valence band (partially filled), conduction band (almost empty).

    • Small electric field required to excite electrons from valence to conduction band.

Conductivity Changes with Temperature

  • At low temperatures, semiconductors behave like insulators.

  • Room temperature sees some conduction.

  • Increased temperature leads to increased conductivity.

  • Negative Temperature Coefficient of Resistance: Conductivity increases with temperature rise.

Classifications of Semiconductors

  • Intrinsic Semiconductors: Pure semiconductors (e.g., silicon, germanium).

  • Extrinsic Semiconductors: Doped semiconductors to increase conductivity.

    • Doping Process: Adding impurities to intrinsic semiconductors.

N-Type and P-Type Semiconductors

  • N-Type: Doping with pentavalent impurities (e.g., phosphorus) adds electrons, making them majority carriers.

  • P-Type: Doping with trivalent impurities (e.g., boron) creates more holes than electrons, making holes the majority carriers.

Theory of PN Junction Diode

  • Formation of a PN Junction by doping one half P-type and the other N-type.

    • Diffusion Process: Movement of electrons and holes across the junction.

    • Potential Barrier: Net positive and negative charge builds at each side, creating a potential barrier (V0) of 0.3V (Germanium) or 0.72V (Silicon).

Forward and Reverse Bias Conditions

  • Forward Bias: Electrons and holes move towards the junction, reducing the depletion region when forward voltage exceeds the potential barrier.

  • Reverse Bias: Increases the depletion width, preventing majority carrier flow, resulting in minimal current.

  • Breakdown: Excessive reverse voltage leading to avalanche breakdown at breakdown voltage, causing high reverse currents.

Applications of PN Junction Diode

  • Used as rectifiers in DC power supplies, switches in logic circuits, clamping and clipping networks, and demodulation circuits.

  • Variants include photodiodes, Zener diodes, light-emitting diodes (LEDs), and laser diodes.

Rectifiers

  • Half-Wave Rectifier: Uses one half of the AC cycle, producing pulsating DC.

  • Full-Wave Rectifier: Utilizes both halves of the AC cycle. May use a center-tapped transformer or bridge configuration.

Bipolar Junction Transistor (BJT)

  • A three-terminal device (Base, Collector, Emitter) utilizing both minority and majority carriers for operation.

  • Current relationships:

    • Emitter current (IE) = Collector current (IC) + Base current (IB).

Common Transistor Configurations

  • Common Base (CB): Emitter input and collector output.

  • Common Emitter (CE): Most widely used; base input and collector output.

  • Common Collector (CC): Emitter output configuration.

Field Effect Transistor (FET)

  • Types: JFET and MOSFET; controlled by an electric field.

  • N-Channel JFET: Majority carriers are electrons; characterized by a source, drain, and gate.

  • MOSFET: Insulated gate structure allowing high input resistance. Types: Enhancement and Depletion.

Power Devices

  • IGBT: Combines the advantages of MOSFET and BJT.

    • Widely applicable in medium power scenarios.

  • SCR (Silicon Controlled Rectifier): A four-layer device acting as a controlled switch.

Commutation Types

  • Natural Commutation: Uses AC sources, enabling zero current to turn off SCR.

  • Forced Commutation: Requires external circuits to achieve zero current in DC applications.

Power Converters

  • Involves converting power between different forms (AC/DC, DC/AC). Types include rectifiers, inverters, and AC controllers.

Linear Voltage Regulators and SMPS

  • Linear Voltage Regulator: Regulates higher input voltage to a stable lower output voltage.

  • Switched Mode Power Supply (SMPS): Converts power effectively, commonly used in computers.

Logic Design Basics

  • Logic Gates Overview: AND, OR, NOT, NAND, NOR, XOR functions.

  • Karnaugh Maps (K-Maps): Tool for minimizing Boolean expressions. Can handle various input variable counts (2, 3, or 4 variables).

Techniques for Minimizing Boolean Functions

  • SOP (Sum of Products) and POS (Product of Sums) forms, including their specific rules for implementation using K-Maps.