Identifying PCB Components for Beginners


You may know that PCBs are comprised of various electrical components like resistors and capacitors. Each component or part has a role in making the entire circuit board.

Each component is fundamental to the functioning of the PCB. It’s also vital for the device to which the PCB will go. If one component fails, then the entire PCB will stop working. It can have an effect on the functioning of the device itself.

Keep reading as this article will glance at each electronic part and explain them briefly. You’ll learn about the categories of electronic parts on circuit boards. You’ll also know how to identify parts on a circuit board briefly.

What is a Printed Circuit Board?

A Printed Circuit Board (PCB) is the baseboard for assembling and interconnecting electronic components. Numerous electronic devices utilize the board. A PCB utilizes copper conductors to make electrical connections between components and support them mechanically.

How do you identify SMD components on a circuit board?

SMD components (Surface-Mount Devices) are electronic parts mounted directly to the PCB surface. It’s done via surface-mount technology.

A standard code system comprising alphanumeric characters identifies the SMD components. This code system varies depending on the component type, like resistors, inductors and capacitors. For example, you can identify SMD capacitors via a 3-digit code.

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Electronic components on circuit boards

The following are the three categories of electronic components on circuit boards:

Passive components

Passive components use present electrical energy and don’t necessitate an external power source to function. They can’t amplify signals. Their examples are resistors, capacitors, inductors, potentiometers, and transformers.

Active components

Active circuit board components necessitate an exterior power source to work. These components can amplify (increase voltage or current) and control electrical signals. Their examples include diodes,  transistors, and integrated circuits (ICs).

Electromechanical components

These parts have both mechanical and electrical components. They can transform electrical energy into mechanical motion or vice versa. Examples are switches and relays.

You should note that sensors can be either passive or active components. It depends on the type and mode of operation of the sensor. With this, let’s look at each common component on circuit boards in more detail:

1. Resistors

Resistors are one of the crucial electronic board components that are the current control foundation. Their function is to reduce the flow of current throughout the board. A resistor does this by actively dissipating electrical energy into heat. Once converted into heat, the resistor dissipates it to cool the whole PCB.

Resistors are built with varied materials and available in different designs. The “axial” form resistors have leads on both ends and a body with colored rings. Made from carbon films, these types of resistors are the most popular ones. With these colored rings, you can know the resistance value as they act as a code.

2. Transistors

Transistors are also vital electronic circuit board components. These parts serve as amplifiers to switch or control the electrical signals in a PCB. They work by amplifying or increasing the small electrical charge coming from the batteries. Thus, transistors ensure the PCB to work properly in this way.

Transistors come in varied types. Typically, you can see a bipolar transistor in a PCB. It has three pins to store and amplify the electrical charge. These are as follows:

  • Base: acts as the cornerstone of the entire transistor
  • Collector: the collector collects the charge carrier
  • Emitter: This region emits or releases charge

PNP (Positive-Negative-Positive) and NPN (Negative-Positive-Negative) are two types of bipolar transistors. Bipolar transistors are widely known as Bipolar Junction Transistors (BJTs).

Field Effect Transistors (FETs) are another transistor variant. These use an electric field to activate and trigger the other circuit.

3. Capacitors

Capacitors are common PCB components. You read earlier that resistors control the electric charge. On the contrary, capacitors function as a part of storing energy. In other words, they keep the electrical charge within the board on a temporary basis.

The capacitors also release the charge whenever the circuit requires more power anywhere. They carry out this by gathering opposite charges on two metal conductive layers. A dielectric or insulating material separates these layers.

The capacitors are mainly classified as conductor or dielectric material. There are varied types of capacitors available. However, radial, ceramic or polyester capacitors are mostly used for PCBs.

You can see that, typically, there are more resistors than capacitors in a PCB.

4. Inductors

Inductors are passive PCB components similar to capacitors. They also accumulate energy in magnetic field form when current flows through them.

The main purpose of inductors is to block or filter out signals within the PCB. It could be interference from another electronic device or equipment. An example is the blocking of interference in radio equipment.

In terms of structure, the most basic inductor is a coil of wire. The greater the number of coils or windings, the more the magnetic field. Hence, more is the inductance. Folded around a magnetic core, these are available in different shapes. It helps in the amplification of the magnetic field and, consequently, the stored energy.

Thus, inductors are integral circuit board parts.

5. Transformers

Transformers are essential PCB board components. These parts are primarily utilized to transfer electrical energy from one circuit to another. It’s done via an increase or decrease in the voltage.

They comprise a soft iron core that has no less than two wound coils of wire. These are the primary coils for the source or first circuit. The other is the secondary coil for the circuit where energy is being received.

The transformer in a PCB continuously increases or decreases the voltage. The purpose is to transform electricity in various circuit board components. They do this transformation via induction technology.

You may assume that transformers are like resistors that control the flow of electricity. The difference is that a transformer isolates the flow of electricity to control it.

6. Diodes

Diodes are fundamental PCB board components. They allow the electrical current to flow only in one direction and not the other. They do this from the anode (i.e., positive terminal) to the cathode (i.e., negative terminal).

The purpose of diodes is to prevent current flow in the wrong direction. Otherwise, the circuit board and the device can get damaged. For this purpose, it has zero resistance in one direction. The other direction has greater resistance.

You can assume the working of diodes as a one-way street. The most widely known diode is the LED (Light Emitting Diode), which gives off light. You must get the orientation right when connecting the LED to a circuit. Otherwise, the LED will not function and can even become damaged.

7. Sensors

Sensors are one of the essential PCB components. These are devices whose function is to detect environmental changes and act consequently.

Sensors produce an electrical signal depending on the change detected. It is then carried to other components in the PCB. Sensors can sense heat, light, noise, moisture, touch, humidity, motion, air quality etc.

They function by converting energy from a physical element into electrical energy. Thus, they are like transducers (transform energy from one form into another).

Their examples can include a resistor variant found in a resistance temperature detector (RTD). It measures temperature. Some sensors can also display environmental changes in a display that is readable to humans.

8. Potentiometers

Potentiometers are also required parts of a circuit board. They are variable resistor forms and have three terminals. These are the resistor, wiper and shaft. The potentiometer’s resistance can be changed manually to control the flow of electrical current. A voltage divider aids in achieving an adjustable output voltage of the circuit.

You’ll find two main types of potentiometers in the market: rotatory and linear. Rotatory potentiometers are more common than linear potentiometers. The rotatory potentiometers utilize a knob for controlling the variable resistance. The potentiometer then controls the voltage output.

You will find rotatory potentiometers in the volume control mechanism of devices like radios.

9. Integrated Circuits

Integrated Circuits (ICs) are the crux of modern electronics. They serve as the heart and brains of most circuits.

An IC comprises electronic components like resistors, transistors and capacitors in quantity of millions. These are all compressed into a tiny chip resembling the small shape of a semiconductor wafer. All components in an IC are packed and connected to meet a common goal.

ICs are soldered onto the Printed Circuit Boards (PCBs). Thus, PCBs are carriers of ICs providing connectivity and support.

Today’s devices like smartphones and powerful computers exist for one reason. It’s due to the large number of components that fit into a single chip.

ICs comprise silicon construction and plastic housing. There are digital and analog ICs. Both are widely used in the PCB manufacturing industry.

10. Switches and Relays

Switches and relays are electromechanical components that use motion to control electricity.

A switch is a power button that allows or blocks electricity flow. It switches between an open circuit and a closed circuit. It controls the electricity flow via the on/off function in a circuit.

If you press the switch down, the switch opens the whole circuit board. It allows functions to take place within the circuit board. When the switch turns off, the electrical functions on the board stop.

Switches can differ in their physical appearance as they can be of different types. Examples include toggle, slider, rotary, push button, lever, key switches and so on.

Likewise, a relay is an electromagnetic switch operating via a solenoid. It means that the relay becomes like a short-term magnet once current flows through it. Relays function as switches and additionally amplify small currents to larger ones.


By now, you must have learned about different circuit board parts. You also got to know the categories to which they belong.

This article also looked at how to identify electronic components in brief.

You might be a beginner or a professional in the electronics industry. By knowing about different parts, you should have a better idea of building a circuit board.