Passive Components in Electronics

Passive Components

• Passive components have inactive functions and do not amplify voltage or rectify supply.
• They are essential for building electronic circuits.
• Common passive components include resistors, capacitors, inductors, transformers, diodes, thermistors, varactors, and transducers.

Resistors

• Resistors control current flow by offering resistance, opposing electric current movement.
• Used to limit current, divide voltage, and set biasing conditions in circuits.
• They are two-terminal devices that are color-coded for identification.

Applications of Resistors

• Vital for circuit functions, allowing current flow.
• Serve as voltage dividers, heating elements, variable resistors, and in timing applications.
• Regulate operations in devices like LEDs and transistors.

Functions in Circuits

• Resistors manage circuit tasks such as motor speed control and amplifier volume adjustment.
• They help in reducing current flow, regulating signal levels, and dividing voltages.

Types of Resistors

• Linear Resistors: Their resistance changes with temperature and voltage. Divided into:

  • Fixed Resistors: Have a specific resistance value, used to set correct circuit conditions.
  • Variable Resistors: Resistance can be adjusted.

• Fixed Resistor Types:

  • Wire Wound Resistors: Made from conductive wire wound around a non-conductive core; used in high power applications.
  • Carbon Film Resistors: Use a carbon film for current limitation; generally fixed value.

Variable Resistors

• Include a sliding contact tapping onto a fixed resistor.
• Types include:
  • Potentiometer: A three-terminal adjustable voltage divider.
  • Rheostat: Manually controls current flow by adjusting resistance.
  • Trimmer Resistor: Mechanically adjustable for fine-tuning resistance.

Non-Linear Resistors

• Respond differently based on voltage or temperature changes.
• Include:
  • Thermistors: Respond to temperature variations.
  • Photo Resistor (LDR): Resistance decreases with increased light intensity.

Capacitors

• Two-terminal devices that store energy as electric charge.
• Consist of two conductors separated by a dielectric material, exhibiting capacitance.
• Charge accumulation occurs creating an electric field across plates.

Diodes

• Allow current to flow in one direction, crucial for rectification.
• Function under two conditions:
  • Forward Bias: Reduced potential barrier, allowing current flow.
  • Reverse Bias: Increases potential barrier, blocking current.

Light Emitting Diodes (LEDs)

• Semiconductor devices emitting light when current flows through them.
• Electrons recombine with holes in the p-n junction, releasing energy as light.
• Doped heavily to produce colored light based on material and doping levels.

Electroluminescence

• The process through which LEDs emit light due to electric current.
• Light intensity increases with the forward voltage.

Energy Concepts

• Valence Band: The outermost electron orbital, occupied by electrons.
• Conduction Band: Higher energy orbitals allowing free movement of electrons, creating current.
• Forbidden Energy Gap: The energy difference between conduction and valence bands, where no electrons exist.

Summary of Bias Conditions

• In forward bias, current flows from positive to negative terminal; electron movement is opposite.
• In reverse bias, electron and hole movement prevents current flow, widening the potential barrier.