An Introduction to Active vs. Passive Electronic Components

Active and passive electronic components are found in everyday items like lights, sound systems, computers, phones, cars, and many more devices.

By definition, active components are found in every single electronic device. Examples include any device with computing power (integrated circuits), devices with a built-in battery or display, and LED lights (light-emitting diodes).

Examples of devices with passive components include incandescent light bulbs, loudspeakers, sensors, microwaves, remote keyless entry systems, and antennas.

Electronic Components: What Are They and What Do They Do?

Most devices have tiny electronic circuits in them that can control machines and process information, and electronic components are used to construct those circuits.

An electronic component is any basic discrete electronic device or physical entity part of an electronic system used to affect electrons or their associated fields.

Electronic components have a number of electrical terminals or leads. These leads connect to other electrical components, often over wire, to create a circuit with a particular function (for example, an amplifier or radio receiver).

Basic electronic components may be packaged discreetly, as arrays or networks of like components, or integrated inside of packages like semiconductor integrated circuits, hybrid integrated circuits, or thick film devices.

What Is an Active Component?

Active components are semiconductor devices that consist of semiconductor materials. They supply electric power to the circuit or power gain in the circuit. Common electronic devices are diodes and transistors, which perform “active” operations like amplifying, rectifying, or converting supplied current (signal).

Semiconductors are substances like silicon or germanium that have a resistance rate somewhere between a conductor (iron, copper, gold, silver, etc.) and an insulator (rubber, ceramic, etc.).

Semiconductor devices can be classified into:

• Single-function discrete (diode, transistor)
• Optical semiconductors such as light-emitting devices (LED, laser), light-receiving devices (photodiode, image pickup element), and optical composite devices (photocouplers, photo relays)
• Sensors capable of detecting temperature, pressure, acceleration, magnetism
• Integrated circuits (ICs) loaded with multiple functions

What Is a Passive Component?

Passive components are required electronic devices that perform “passive” operations like consuming, storing, or releasing electric power. They can only absorb electrical energy and dissipate it in the form of heat or store it in a magnetic or electric field. They cannot provide electric power or power amplification in an electric circuit. Common passive components include resistors, capacitors, and coils.

Functions of Active and Passive Components

Functions of Active Components

• Diodes
  A diode is a component capable of passing electric current in one direction but stopping current in the opposite direction (rectifying characteristics). This is done by combining semiconductors of type-p and type-n, and two types of materials, such as a semiconductor and a metal. LED (light-emitting diode) is also a type of diode, which is known for emitting light, but has the same characteristic of passing current only in one direction.
• Transistors
  Transistors are semiconductor devices made by joining p-type and n-type semiconductors one after another and having three terminals called base (B), collector (C), and emitter (E). When a small current is applied between the base and emitter, a much larger current flows between the collector and emitter as an amplifying function. Similarly, a change in current between the base and emitter causes a large change in current between the collector and emitter as a switching function. Thus, transistors provide two functions. Transistors have a wide variety of applications, including an amplifier circuit, a switching circuit, a constant voltage circuit that suppresses power voltage fluctuation, and a logic circuit that uses input and output voltages for local operation.
• Integrated Circuit (IC)
  Integrated circuits use semiconductor processing technology called photolithography to form multiple electronic components on a circuit substrate such as minute transistors and diodes on a semiconductor wafer. Types of ICs are largely grouped into digital ICs for handling signals and analog ICs for handling analog signals. These components are a central control function of electronic equipment, such as complex data computation, conversion process, and data memory.

Functions of Passive Components

• Resistors
  Resistors maintain or change electric current that flows in the circuit by consuming supplied electric power. For example, a simple circuit could consist of a power supply and a resistor. While maintaining a constant power supply, if the resistor value is increased, the current in the circuit will get smaller. If the resistor value is decreased, the current gets larger. In actual circuits, resistors are used to suppress current to avoid allowing more flow than the rated value into other components. They can also be used to obtain the required current or voltage by dividing voltage or current flow, or for measuring the flow in the circuit.
• Capacitors
  Capacitors store or release supplied electrical power (electrical charge) by blocking direct current (DC), while passing alternating current (AC). They pass high-frequency currents very well. When DC is applied to a capacitor, it stores electrical charge to a maximum level and then stops the current flow. When AC is applied, the capacitor stores and releases electrical charge every time the current flow direction changes. How much electrical charge can be stored in a capacitor is called capacitance. The higher the capacitance or the higher the frequency of AC, the more current flows through.
• Inductors (Coil)
  A coil’s function is to convert electricity (current) into a magnetic field or convert a magnetic field into a current. Coils pass DC but shut off AC, and it becomes difficult to pass current when the frequency gets higher. A coil’s behavior toward DC and AC is opposite that of capacitors. Applying electrical current to wiring generates a magnetic field, but coils can store electrical energy as a magnetic field through their winding structure of coil. DC passes through a coil as it does a conductor, but AC generates a largely changing magnetic field by changes in current.

What Is the Difference Between Active and Passive Components?

Active components require an external source to operate in a circuit, while passive components do not. Active components produce energy in the form of voltage or current, and passive components store or maintain energy in the form of voltage or current.

Here are some other differences between active and passive components:

A simple way to test whether a component is active or not is to measure the difference between its input and output signals. If there is a decline in power, the component is passive. If the signal is amplified, it is active.

All electronic circuits must contain at least one active component, and most electronic devices contain both active and passive components.

Become a Certified Electronics Technician at Erie Institute of Technology

If you want to work on the high-tech devices that make our world possible, you should consider enrolling in the Electronics Technician Training Program at EIT.

Upon completion of this 12 to 18-month program, you’ll have the technical expertise needed to install, troubleshoot, and maintain electronic equipment. Plus, you could go on to specialize in Biomedical Equipment Technology or Industrial Automation & Robotics Technology.

Apply online today or visit our website to learn more about our programs.

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