Semiconductor electronics form the backbone of modern electronics, enabling the creation of compact, efficient, and versatile devices that power our world. This summary explores the key concepts in this field, from the materials themselves to their applications in various electronic devices.
1. Semiconductor Materials
- What are Semiconductors? Materials with electrical conductivity between conductors (like metals) and insulators (like ceramics). Their conductivity can be controlled by factors like temperature, impurities, or applied voltage.
- Key Examples: Silicon (Si) and Germanium (Ge) are the most common semiconductors.
- Energy Bands: The electrons in semiconductors are arranged in energy bands. The valence band (filled with electrons) and the conduction band (mostly empty) are separated by a small energy gap.
- Intrinsic Semiconductors: Pure semiconductors with no impurities. Conduction occurs due to thermal excitation of electrons across the energy gap, creating electron-hole pairs.
- Extrinsic Semiconductors: Conductivity is enhanced by adding impurities (doping) to create:
- n-type: Doped with pentavalent impurities (like phosphorus), creating excess free electrons.
- p-type: Doped with trivalent impurities (like boron), creating “holes” (missing electrons) that act as positive charge carriers.
2. Semiconductor Devices
- p-n Junction Diode: Formed by joining p-type and n-type semiconductors. It allows current flow in one direction (forward bias) and blocks it in the opposite direction (reverse bias).
- Applications: Rectification (converting AC to DC), voltage regulation, signal detection.
- Zener Diode: A special diode designed to operate in the reverse breakdown region at a specific voltage.
- Applications: Voltage regulation, voltage reference.
- Light Emitting Diode (LED): Emits light when current flows in the forward direction.
- Applications: Indicators, displays, lighting.
- Photodiode: Converts light into current.
- Applications: Light detection, optical communication.
- Transistors: Three-terminal devices that amplify or switch electronic signals.
- Bipolar Junction Transistor (BJT): Consists of two p-n junctions. Current flow between the collector and emitter is controlled by the base current.
- Field-Effect Transistor (FET): Controls current flow between the source and drain by the voltage applied to the gate.
- Applications: Amplification, switching, oscillators, integrated circuits.
3. Simple Circuits
- Rectifier Circuits: Convert AC to DC using diodes.
- Half-wave Rectifier: Uses a single diode to allow only one half-cycle of the AC waveform to pass.
- Full-wave Rectifier: Uses a bridge rectifier (four diodes) to convert both half-cycles of the AC waveform.
- Amplifier Circuits: Use transistors to increase the amplitude of electronic signals.
- Common Emitter Amplifier: A common configuration for BJTs, providing high voltage and current gain.
- Oscillator Circuits: Generate AC signals using transistors and feedback networks.
- LC Oscillator: Uses an inductor (L) and capacitor (C) to create oscillations at a specific frequency.
4. Integrated Circuits (ICs)
- Miniaturization: ICs combine multiple transistors, diodes, resistors, and capacitors on a single semiconductor chip, enabling complex circuits in a small space.
- Applications: Microprocessors, memory chips, logic gates, and countless other electronic systems.