Electronics Circuit Passive Components

• Electronics circuit devices and analysis
• Prepared by Prof Keith Hezekiah H. Presno

Passive Components

• Passive components do not need external power to operate
• Passive components cannot amplify or increase signal power
• Passive components modify but do not generate signals
• They operate based on the material's properties
• Primarily attenuate or modify the signal passing through them
• Ideally, behave linearly where output is proportional to input
• Passive components are fundamental building blocks in electronics circuits

Examples of Passive Components

• Capacitors store electrical energy in an electric field
• Inductors store electrical energy in a magnetic field
• Basic diodes primarily control the direction of current flow, some exhibit active behavior
• Transformers transfer electrical energy through electromagnetic induction
• Crystals are used for precise timing in oscillators

Resistor

• Opposes electric current flow, controlling the amount of current in a circuit
• Dissipates energy in the form of heat
• Resistance is measured in ohms (Ω)
• Power rating is measured in watts (W)
• Applications include current limiting, voltage division, plus pull-up/pull-down in digital circuits

Capacitor

• Stores electrical energy in an electric field
• It comprises two conductive plates separated by a dielectric
• Capacitance is measured in farads (F)
• Voltage rating is the maximum voltage it can handle
• Ceramic capacitors feature small but stable capacitance
• Electrolytic capacitors feature high capacitance and are polarized
• Film capacitors feature high precision and are non-polarized
• Used for filtering, e.g., smoothing power supply ripple
• Used for coupling and decoupling signals
• Used for energy storage, e.g., in flash circuits

Inductor

• Stores energy in a magnetic field when current flows, opposing changes in current
• Inductance is measured in Henries (H)
• Current rating is the maximum current that it can handle
• Air-core inductors feature low inductance with no core loss
• Iron-core inductors are compact with minimum electromagnetic interference
• Used for filtering, e.g., in LC filters
• Used for energy storage, e.g., in switch-mode power supplies
• Used for impedance matching

Transformer

• Transfers electrical energy between two or more circuits via electromagnetic induction
• Primary and secondary windings are wrapped around a core
• Turns ratio determines voltage transformation
• Power rating signifies its max power handling
• Step-up transformers increase voltage
• Step-down transformers decrease voltage
• Isolation transformers provide electrical isolation
• Applications include voltage step-up/down in power supplies
• Applications impedance matching in audio systems
• Applications isolation in safety-critical circuits

Diode

• Passive in certain contexts, allowing current flow in one direction
• Functions as a one-way valve for electric current
• Forward voltage drop is typically 0.7V for silicon diodes
• Reverse breakdown voltage is the other key parameter
• Rectifier diodes are used in power supplies
• Zener diodes are used for voltage regulation
• Light-emitting diodes (LEDs) emit light when forward-biased
• Used for rectification (converting AC to DC)
• Used for voltage regulation with Zener diodes
• Used for signal demodulation

Fuse

• Acts as a safety device that protects circuits from overcurrent
• Breaks the circuit when current exceeds a specified value
• Current rating is the maximum current it can handle
• Breaking capacity is the maximum current it can interrupt
• Fast-acting fuses quickly respond to overcurrent
• Slow-blow fuses tolerate temporary surges
• Applications include overcurrent protection in power supplies
• Applications circuit protection in automotive and industrial systems

Potentiometer

• Potentiometers are also called variable resistors
• Works as a three-terminal resistor with adjustable sliding contact to work as a voltage divider
• Resistance range (e.g., 0 - 10 kΩ) plus taper (linear or logarithmic) matters
• Used for volume control in audio systems
• Used for brightness control in displays
• Used for calibration and tuning in circuits

Thermistor

• A thermistor is a temperature-sensitive resistor
• Resistance changes with temperature
• Measured for resistance at a reference temperature (e.g., 25°C)
• Measured for temperature coefficient (positive or negative)
• NTC (Negative Temperature Coefficient) sees resistance decrease with temperature
• PTC (Positive Temperature Coefficient) sees resistance increase with temperature
• Used for temperature sensing and control
• Used for overcurrent protection with PTC thermistors
• Used for compensation in circuits

Varistor

• Varistors are also called voltage-dependent resistors
• Protects circuits from surges/voltage spikes
• Changes resistance with applied voltage
• Clamping voltage is the voltage at which it starts conducting
• Energy absorption capacity is also key
• Used for surge protection in power supplies
• Used for protection against lightning strikes

Crystal Oscillator

• It uses the mechanical resonance of a vibrating crystal
• Generates a precise electrical signal with a specific frequency
• Frequency (e.g., 4 MHz, 16 MHz) matters
• Stability (e.g., ±10 ppm) matters
• Used for clock generation in microcontrollers and digital circuits
• Used for frequency control in communication systems

Active Components

• Active components need an external power source
• Can amplify signals
• Offer signal control
• Convert energy
• Building blocks for "intelligence" and circuit functionality
• They can amplify signals, switch signals, or perform logic operations
• Behavior is often non-linear
• Output signal is not simply proportional to the input signal
• Used for complex circuits with advanced capabilities

Examples of Active Components

• Transistors (BJTs, FETs) amplify current or voltage as switches.
• Diodes exhibit active characteristics, e.g., Zener, varactor, tunnel diodes
• Integrated Circuits (containing transistors, resistors, etc. on a chip)
• Operational Amplifiers (Op-Amps) amplify analog signals
• Microprocessors (MPUs) are general-purpose processors in computers and embedded systems
• Microcontrollers (MCUs) are self-contained systems-on-a-chip with a processor, memory, etc.
• Logic Gates perform basic logic operations
• Memory Chips (RAM, ROM) store digital data
• Vacuum Tubes amplify signals
• Thyristors (SCRs, Triacs) control AC power.
• Light Emitting Diodes (LEDs) convert electrical energy into light.