Component Classifications (Part 1)

Components are the basic building blocks in electronic circuits. They come in all shapes and sizes and perform different functions based on their electrical characteristics, some of which are simple and straightforward, while others are complex and cascaded in nature,

Generally, components are classified into discrete and integrated, the former being a single entity or unit, while the latter is made up of multiple discrete entities ranging from a few to over a million, depending on the manufacturing process and technology. These are further differentiated into passive and active components, the former requiring no external sources to power or operate, whereas the latter uses and manipulates energy to effect gain or change in a signal's condition.

Passive Discrete Components

Some examples of passive discrete components are shown in the photos below:

The resistor is one of the most basic element in an electrical circuit. Types of resistor include carbon composites, chip SMDs, PTC thermistors, aluminum clads, and networks. Second only to resistors, capacitors are one of the most common components you'll find on PCBs. Types of capacitor include electrolytics, micas, chip SMDs, radial-lead ceramics, and axial-lead tantalums.

Together with resistors and capacitors, inductors belong to the same passive linear circuit elements found in electrical circuits. Inductors and capacitors are two types of energy storage elements—the former deals with current while the later with voltage. Types of inductor include axial-lead, radial-lead, torroids, ferrite-cores, unshielded and shielded SMDs.

A fuse is a kind of resistor with low resistance and built to tolerate a certain amount of current, which if exceeded, will cause it to blow up and become an open. In other words, it's a protection device. Types of fuse include axial-lead, glass cartridges, radial, SMDs, resettable and blade.

Most relays are electro-mechanical in structure in which contacts make-and-break by means of a relay coil being energized or de-energized by a control voltage. For this reason, they are also called electrically operated switches. Types of relay include electro-mechanical, reeds, TO-5, SMDs, solid-state and hermetically sealed.

It is important to be able to identify these discrete components when doing PCB reverse engineering, especially with modern surface-mounted boards where such components are shrinking in size and their markings on the PCB are kept to a minimum.