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What are passive components?
2022-11-21 15:52
Passive components include a wide range of parts such as resistors, capacitors, and inductors. Simply put, devices that require an external power source are called active components, while those that do not are referred to as passive components. Active components are typically used for signal amplification, conversion, and similar functions, whereas passive components serve to transmit signals or to achieve directional “signal amplification.” Now, let’s explore what passive components are!
Passive components include a wide range of parts such as resistors, capacitors, and inductors. Simply put, devices that require an external power source are called active components, while those that do not need one are referred to as passive components. Active components are typically used for signal amplification, conversion, and similar functions, whereas passive components serve to transmit signals or to achieve directional “signal amplification.” Now, let’s explore what passive components are!
Passive components are the term used in Taiwan’s electronics industry to refer to certain electronic parts, distinguishing them from active components. In mainland China, they are known as passive and active devices, respectively. From the perspective of their operating characteristics, passive components either do not consume electrical power themselves or can convert electrical energy into other forms of energy; they also have the property of functioning normally when a signal is applied, even without an external power supply. Active components, on the other hand, are those that can perform data computation and processing within a circuit. Semiconductor devices such as transistors, integrated circuits, picture tubes, and various display chips all fall under the category of active components. Passive components, by contrast, do not alter the fundamental characteristics of a signal; they merely allow the signal to pass through without modification. Common examples include resistors, capacitors, inductors, and transformers, which will be discussed in detail below.
1. Inductor
An inductor is a coil wound from insulated wire. It is a component that can convert electrical energy—specifically, reactive power—into magnetic energy and store it; in simple terms, it is just a coil. When current flows through the coil, an electromotive force is induced, which is referred to as inductance. The magnetic flux generated during this process is called inductance.
Inductors are also among the most commonly used components in electronic circuits, accounting for approximately 10% to 15% of the total auxiliary component consumption. In particular, the downstream trend toward lighter, thinner, shorter, and smaller electronic end products makes the miniaturization and chip‑integration of upstream electronic components an inevitable development path. At present, chip inductors constitute the majority of China’s inductor output, and their market share is expected to expand in the future.
2. Resistor
Resistors function to regulate voltage and current in a circuit, and can be classified into three types based on the material and packaging method.
1) Fixed non‑chip resistors. These products are primarily used to handle power and signal applications, with strong demand in electronic devices such as power supplies and monitors.
2) Fixed chip resistors, which are widely used in information technology, telecommunications, home appliances, and various instruments and meters.
3) Thermistors and variable resistors are primarily used for temperature sensing or control, motor protection and starting devices, and overcurrent/voltage protection devices.
Resistors are primarily used in circuits to regulate and stabilize current and voltage; they can serve as shunt resistors and voltage dividers, and they can also match circuits to their loads.
3. Capacitor
A capacitor isolates two conductive materials with a dielectric, thereby storing any static electricity that may accumulate. Capacitors come in many varieties; based on the materials used, they can be classified into more than 30 types. Domestically, manufacturers primarily produce aluminum electrolytic capacitors, ceramic capacitors, and plastic‑film capacitors. Among these, the multilayer ceramic capacitor (MLCC), a type of ceramic capacitor, is particularly common. In essence, ceramic capacitors are divided into single‑layer ceramic capacitors and multilayer ceramic capacitors (MLCCs). Thanks to their small size, relatively high capacitance, low loss at high frequencies, and excellent stability, MLCCs are widely employed in motherboards, laptops, mobile phones, scanners, optical drives, modems, and other devices—meeting the growing demand for compact, lightweight electronic products. The primary functions of capacitors include storing electrical charge, serving as AC filters or bypasses, blocking DC voltage, and providing tuning and oscillation capabilities; they are used in circuits for signal coupling, decoupling, filtering, tuning, energy conversion, and control applications.
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