Basic Concepts and Identification: Opening the Door to Electronics

Functions and Roles: A Precise Teamwork Symphony

Parameter Selection: The Key to Reliability

Expanded Types: Meet More PCB “Residents”

Testing and Repair: Fast Diagnosis and Fix

Frequently Asked Questions

At the heart of electronic devices, a green or black board—called a Printed Circuit Board (PCB)—acts like the base of a mini city. The PCB components (electronic components) are the core units that give this "city" its function. These parts have specific electrical functions. They work together to control current, process signals, store energy, and connect circuits. These actions help devices work—from phones to satellites. Knowing these “building blocks” is key for design, repair, and innovation.

Electronic components are the physical base parts of electronic systems. Their main jobs are to control current and voltage, process signals, store energy, and connect circuits. Correct identification is the first step in engineering.

Passive Components: Work without power supply.

• Resistor (R): Uses a rectangle or zigzag symbol. Comes in cylindrical (through-hole) or rectangular (SMD) shape. Function: limit current, divide voltage, and keep the circuit stable. Value marked with color bands or numbers.
• Capacitor (C): Uses parallel line or curved symbol. Comes in ceramic disc, aluminum electrolytic cylinder, or tantalum block shape. Function: store charge, block DC, pass AC, filter noise. Shows capacitance (e.g., 10µF) and voltage rating (e.g., 25V).
• Inductor (L): Uses coil symbol. Comes in wire-wound magnetic core or SMD block. Function: store magnetic energy, resist AC change, build resonant circuits. Value marked with bands or numbers.

Active Components: Need power to work.

• Diode (D): Uses a triangle and line symbol. Has polarity mark (cathode stripe). Function: one-way current, voltage regulation (Zener diode), light emission (LED), fast switching (Schottky diode).
• Transistor/MOSFET (Q): Uses arrow symbols (for BJT) or gate lead (for MOSFET). Function: amplify current/voltage, control power switching.
• Integrated Circuit (IC, U): Uses rectangle with pins. DIP/SOP/BGA package. Combines many parts to handle CPU, memory, power management, etc. Has model code laser-marked on surface.

Five Quick Identification Tips

• Look at shape and color: Electrolytic capacitors are cylinders; tantalum capacitors are blocks with polarity stripe.
• Read markings: Resistor color bands, capacitor codes (e.g., 104 = 100nF), IC models (e.g., STM32F4).
• Check polarity marks: Diode stripe is cathode; IC notch shows pin 1.
• Understand position logic: Large capacitors near power input; crystal near CPU.
• Use online databases: Tools like Octopart help decode markings.

THT vs SMD Package Comparison

Advantage 1: SMD saves space. For example, modern 0201 capacitors are 90% smaller than traditional ones, helping make phones and wearables thinner.

Each component has a role. Together, they make circuits work.

• Signal Processing Chain: Sensor collects signal → Op-Amp IC amplifies → LC filter removes noise → ADC converts to digital → MCU processes data.
• Power Management Flow: Power input → Fuse protection → Bridge rectifier turns AC into DC → Capacitor smooths voltage → Regulator IC gives stable output.
• Logic and Action: MCU sends commands → Logic gates decode → MOSFET drives motor or lights up LED.
• Passive Components Support: Resistors set voltage levels, capacitors store energy and reduce surges, inductors block high-frequency noise. They create a stable base for active parts.
• Key Cooperation: An Op-Amp (active) needs exact resistor (passive) values to set gain. If not, accuracy drops over 50%.

Choosing the wrong component causes failure! Know the main parameters:

General Parameters:

• Voltage rating (> 150% of working voltage)
• Current rating (> peak load)
• Power rating (use with margin)
• Temperature range (industrial: -40~85°C)

Component-Specific Parameters:

• Capacitor: Capacitance, ESR (Equivalent Series Resistance; lower ESR = less ripple), material (ceramic NP0 stable at high temp, aluminum electrolytic is cheaper).
• Transistor: Vceo/Vdss (voltage rating), Ice/Id (current), hFE (gain).
• MOSFET: Rds(on) (on-resistance, affects efficiency), Qg (gate charge, affects switching speed).

Selection Logic Map:

Function → 2. Parameter Match → 3. Environment Fit → 4. Package Size → 5. Reliability Check

Advantage 2: High-end solid capacitors have ESR as low as 5mΩ (vs ~500mΩ for normal ones). They handle 3× more ripple current and last over 5000 hours vs 2000 hours.

Besides basic parts, PCBs also have:

Power Backbone:

• Three-terminal regulator (e.g., 78L05 gives 5V): TO-92 (low power), TO-220 (good heat dissipation).
• DC-DC converter IC: Boost or buck voltage. More efficient and cooler than linear regulators.

Signal Guards:

• MOV (Metal Oxide Varistor): Absorbs surge voltage to protect ports.
• Optocoupler: Isolates high and low voltage circuits. Reduces noise.

Digital Heartbeat:

• Crystal/oscillator: Metal-can with 2 or 4 pins. Gives precise clock (e.g., 32.768kHz).

Connection Hub:

• USB-C connector: Handles fast data and charging.

Fixing broken devices needs smart testing methods:

Tools You Need:

• Multimeter: Checks continuity and voltage. In diode mode, test LED Vf (~2V).
• Oscilloscope: Shows signal shape. Finds power ripple over limit (e.g., >50mV).
• Thermal Camera: Quickly finds hot spots (e.g., shorted MOSFET at 200°C).
• Magnifier: Finds cracks, cold solder joints (dull), or bulged capacitors.

Typical Fault Table:

Repair Tips:

• 50% of faults are in the power section: First check fuse, rectifier, main capacitor, and regulator IC.
• Capacitor issues cause 70% of passive part failures: Electrolytic types often dry or bulge. Replace with 105°C-rated, low-ESR models for longer life.

Advantage 3: When replacing MOSFETs, use SiC (Silicon Carbide) types. They cut switching loss by 80%, boost system efficiency by 5–10%, and reduce heat a lot.

Where can i buy circuit board components?

Depending on your location, budget, and specific requirements, circuit board components can be sourced from various global distributors, including Mouser Electronics, Arrow Electronics, Farnell/Element14, RS Components, and others.

What is a circuit board?

A circuit board is a thin insulating board (often fiberglass or plastic) that connects electronic components electrically and mechanically.

How circuit board components work?

On a circuit board, components work by managing electrical signals through control, storage, and processing. Passives regulate current, store energy, or pass/block signals without needing power. Actives, requiring a power source, amplify signals, switch currents, or perform computations.