Learn How Capacitors Function in Electronic Circuits

2024-03-24

Capacitors are essential components in electronic circuits, performing various functions to ensure proper operation. One of the primary functions of capacitors is to store and release electrical energy, which helps in filtering and regulating the flow of current. They also play a crucial role in blocking direct current while allowing alternating current to pass through.

Capacitors can be used for timing circuits, noise filtering, energy storage, and voltage regulation, making them versatile and valuable in a wide range of electronic applications.

Understanding the function of capacitors can greatly benefit engineers, technicians, and electronics enthusiasts in designing and troubleshooting electronic systems. We will introduce it by 8 key functions.

1. What are capacitors used for?

Capacitors are a basic component of electronics and are an integral accessory to a host of applications. The most common use for capacitors is energy storage, power conditioning, electronic noise filtering, remote sensing and signal coupling/decoupling. Due to the fact that capacitors are an important and versatile function to varied applications, they are used in a wide range of industries.

However, you may be wondering what are capacitors used for and what exactly do they do? Considering they play an important function to many devices we utilise today, here are some of the most common uses of capacitors and their function.

2. What do capacitors do? 

 Capacitors are devices that are designed to store electrical charge in an electric field. They have two electric conductors that are separated by a dielectric material. Both conductors are intended to accumulate charge when connected to a power source – one receives negative charge, the other received positive. Unlike a resistor, a capacitor does not dissipate energy

A capacitors capacitance – the ratio of the amount of electric charge that is stored on a conductor to a difference in electric potential – distinguishes an ideal capacitor from a poor one. Typically, the closer two conductors are and the larger their surface area, the greater a capacitors capacitance is.

3. Power supply decoupling 

 What are capacitors used for? Well, one of the most common applications a capacitor is used for is to decouple one part of a circuit from another. This process is done when an incoming line signal is taken through a transformer and a rectifier, resulting in an uneven waveform.

4.  AC coupling & DC blocking 

 A common function of a capacitor is to separate the AC and DC components of a signal. A capacitor will work to allow AC signals to pass from one section of a circuit to the other while blocking DC static voltage. In this function, it is essential to ensure that the impedance – the amount of opposition that the capacitor presents to the voltage – is suitably low.

5. Energy Storage 

Capacitors have been an energy storage application since the late 18th century, although individual capacitors do not generally hold a great deal of energy. They will typically only provide enough power for electronic devices to use during temporary power outages or when they need additional power.

6. Various types of capacitors and their characteristics 

If electronic circuits are likened to a baseball field, various capacitors occupy different positions according to their respective strengths. Paper capacitors, which used to be the “star players” of circuits, are no longer regulars, but some older capacitors like mica capacitors are still active. The most common type of capacitor is the multilayer ceramic chip capacitor. This is because they are small, highly reliable, and come in a wide variety of types to suit any position. Electrolytic capacitors are the noticeably larger, “dependable” type. They are characterized by their high capacitance, which allows them to store a large amount of electric charge, and are indispensable in applications such as strobe lighting in digital cameras. Electrolytic capacitors are also called discharge capacitors.

7. Why do aluminum electrolytic capacitors have high capacitance? 

A capacitor consists of two electrodes facing each other. The capacity of the stored charge, or capacitance (C), increases as the electrode surface area (S) increases, the distance between the electrodes (d) decreases, and the relative dielectric constant (εr) of the dielectric material (insulator) between the electrodes increases.

The most common type of capacitor with a capacitance of 100 µF (microfarad) or more is the aluminum electrolytic capacitor. This capacitor is made by chemically roughening the surface of high-purity aluminum and forming a thin oxide film on the anode surface by electrolysis, which serves as a dielectric material. The rough surface with fine irregularities allows for a large electrode surface area—and since the oxide film is very thin, a capacitor with substantial capacitance can be realized. For mobile devices and notebook PCs, tantalum electrolytic capacitors are also used, as they are compact, have higher capacitance, and are more reliable than aluminum electrolytic capacitors. However, tantalum is a rare metal and therefore more expensive.

Ceramic capacitors are made from a unique ceramic material (dielectric ceramics) with an extremely high dielectric constant. While the relative permittivity (dielectric constant) of air is about 1, the plastic film used in film capacitors is about 2 to 3, and the oxide film used in electrolytic capacitors is 8 to 10. However, ceramic dielectric materials, such as barium titanate and other high-permittivity ceramic materials, have permittivities of 1,000 to 20,000. Multilayer ceramic chip capacitors with a capacitance in the high range of electrolytic capacitors, despite their small size, can be manufactured by laminating many sheets of this ceramic dielectric material and metal electrodes in layers.

8. Why do aluminum electrolytic capacitors have high capacitance?  

A capacitor consists of two electrodes facing each other. The capacity of the stored charge, or capacitance (C), increases as the electrode surface area (S) increases, the distance between the electrodes (d) decreases, and the relative dielectric constant (εr) of the dielectric material (insulator) between the electrodes increases.

The most common type of capacitor with a capacitance of 100 µF (microfarad) or more is the aluminum electrolytic capacitor. This capacitor is made by chemically roughening the surface of high-purity aluminum and forming a thin oxide film on the anode surface by electrolysis, which serves as a dielectric material. The rough surface with fine irregularities allows for a large electrode surface area—and since the oxide film is very thin, a capacitor with substantial capacitance can be realized. For mobile devices and notebook PCs, tantalum electrolytic capacitors are also used, as they are compact, have higher capacitance, and are more reliable than aluminum electrolytic capacitors. However, tantalum is a rare metal and therefore more expensive.

Ceramic capacitors are made from a unique ceramic material (dielectric ceramics) with an extremely high dielectric constant. While the relative permittivity (dielectric constant) of air is about 1, the plastic film used in film capacitors is about 2 to 3, and the oxide film used in electrolytic capacitors is 8 to 10. However, ceramic dielectric materials, such as barium titanate and other high-permittivity ceramic materials, have permittivities of 1,000 to 20,000. Multilayer ceramic chip capacitors with a capacitance in the high range of electrolytic capacitors, despite their small size, can be manufactured by laminating many sheets of this ceramic dielectric material and metal electrodes in layers.

Feel free to reach out if you have any specific questions regarding the function of capacitors or any other electronic components.