<< Click to Display Table of Contents >> Navigation:  Background Theory > Part Design > Passive Parts

Passive electronic parts are components that do not require a power source to operate and can only control or store electrical signals. These parts typically use materials such as ceramic, plastic, or metal to manipulate the flow of electricity.

Examples of passive electronic parts include:

Resistors

These are components that resist the flow of electrical current. They are used in a wide range of electronic circuits to limit current, divide voltage, or control timing.

PCB resistors, often referred to as surface mount resistors or SMD resistors, are electronic components that limit or regulate the flow of electrical current in an electronic circuit.

Resistors are fundamental components in electronics and are found in almost all electronic devices. They're used in a wide range of applications, including setting the gain of an amplifier, dividing voltage, carrying out basic logic operations, and many other functions.

SMD resistors are designed to be mounted on the surface of a PCB. Unlike older, through-hole resistors, which have leads that pass through the board and are soldered on the other side, SMD resistors are soldered directly onto pads on the surface of the board.

SMD resistors come in various standard sizes. The size is usually denoted by a three- or four-digit number, such as 0603, 0805, or 1206. The first two digits represent the length and the last two digits represent the width, both in hundredths of an inch. For example, an 0603 resistor is 0.06 inches long and 0.03 inches wide.

The resistance value of a resistor is usually marked on its body using a numerical code. For SMD resistors, a common system is the EIA-96 code, which uses a three-digit number to represent the resistor's value and tolerance.

It's important to remember that resistors, like other electronic components, should be chosen and used according to the requirements of the specific circuit and application, taking into account factors like the required resistance, power rating, tolerance, temperature coefficient, and other parameters.

Capacitors

These are components that store electrical energy in an electric field. They are used in electronic circuits to smooth out voltage fluctuations, filter out noise, or block direct current.

Capacitors in a Printed Circuit Board (PCB) are electronic components that store and release electrical energy. They play a vital role in various aspects of electronic circuit design, including filtering, decoupling, energy storage, signal coupling or decoupling, electronic noise filtering, and tuning of some communication circuits.

Much like resistors, capacitors come in a variety of types and sizes, with the two most common being through-hole and surface-mount (SMD) capacitors.

Through-Hole Capacitors: These types of capacitors have long leads that can be threaded through the holes on the PCB and then soldered to pads on the other side. Through-hole capacitors were widely used in older electronic devices.

Surface-Mount Capacitors (SMD Capacitors): These types of capacitors are soldered directly onto the surface of the PCB, which makes them a more space-efficient choice. They are the most common type of capacitor found on modern PCBs. They come in standard sizes denoted by a three- or four-digit number, much like SMD resistors.

Capacitors vary widely in their specific properties, including their capacitance value (measured in farads), voltage rating, temperature stability, and equivalent series resistance (ESR). Different types of capacitors (e.g., ceramic, electrolytic, tantalum, etc.) have different properties, which makes them suitable for different applications.

The specific value of a capacitor is typically printed directly on the component, although for smaller SMD capacitors, this may not always be the case due to size limitations.

In a circuit, capacitors can be used for a variety of functions, such as smoothing in power supply applications, filtering in audio circuits, and for timing applications with resistors and capacitors forming RC (resistor-capacitor) circuits.

Inductors

These are components that store electrical energy in a magnetic field. They are used in electronic circuits to filter out high-frequency noise, control current, or store energy.

Inductors on a Printed Circuit Board (PCB) are passive electronic components that store energy in the form of a magnetic field when an electric current is passed through them. They're often used in filter circuits, power supply circuits, and RF (radio frequency) circuits, among other applications.

Inductors are characterized by their inductance value, which is measured in Henries (H), and their current rating. The inductance value determines how much energy the inductor can store: the higher the inductance, the more energy stored for a given current. The current rating is the maximum amount of current the inductor can handle without overheating or becoming damaged.

Like resistors and capacitors, inductors can come in through-hole or surface mount (SMD) varieties:

Through-Hole Inductors: These inductors have leads that are inserted into holes on the PCB and soldered to pads on the other side. They're typically larger and used in applications where higher power handling and inductance values are needed.

Surface Mount Inductors (SMD Inductors): These inductors are soldered directly onto the surface of the PCB. They're smaller and used in applications where space is at a premium, like in modern, compact electronic devices.

The physical size and shape of an inductor can vary widely depending on its inductance value, current rating, and intended application. Some inductors are simple coils of wire, while others are wound around a magnetic core to increase their inductance. There are also air core inductors, ferrite core inductors, and toroidal inductors, among others.

Inductors, because of their ability to oppose changes in current, are often used in circuits that need to smooth out changes in voltage or current, filter out certain frequencies, or store energy for later use. They're a key component in many types of electronic devices, from simple power supplies to complex RF transceivers.

Transformers

These are components that transfer electrical energy from one circuit to another through electromagnetic induction. They are used in electronic circuits to step up or step down voltage, isolate circuits, or match impedance.

Overall, passive electronic parts are critical components of electronic circuits and are used to control, store, or filter electrical signals in a wide range of applications.

Transformers in a Printed Circuit Board (PCB) are passive electrical devices that transfer electrical energy from one circuit to another through the process of electromagnetic induction. They are typically used to increase or decrease voltage levels between circuits, making them essential components in power supply designs.

Transformers consist of two or more coils of wire, known as windings, which are wrapped around a core, often made of ferrite or iron. When alternating current (AC) flows through one winding, it generates a magnetic field in the core, which then induces a voltage in the other winding. The ratio of turns between the primary (input) winding and the secondary (output) winding determines the voltage transformation.

PCB transformers come in a variety of types, including:

Through-Hole Transformers: These are typically larger and are soldered into holes on the PCB. They're used when larger power handling is required.

Surface Mount Transformers (SMD Transformers): These are designed to be soldered directly onto the PCB, making them a more space-efficient choice. They are often used in low-power applications where space saving is critical.

Planar Transformers: These are a type of SMD transformer that use PCB traces for their windings, which can offer better performance and integration but at a higher manufacturing cost.

Transformers used in PCBs can have a wide range of specifications depending on their intended application. They may be designed for different frequency ranges (from audio frequencies to RF), different power levels, different impedance matching requirements, and different isolation requirements, among other factors.

Transformers are used in a variety of applications including power supplies, audio systems, telecommunications, and RF circuits. It's important to choose the correct transformer for your specific application, taking into account factors such as power requirements, operating frequency, and the required voltage transformation ratio.