Everything you need to know about capacitors

Capacitors are essential electronic components that store and release electrical energy. They are similar to batteries, however they work in rather different ways. While both are used for energy storage, batteries have two terminals where chemical reactions produce and absorb electrons when a circuit is created, whereas capacitors are simpler because they can't generate new electrons - they only store them. In this article, we will explore what capacitors are, what they do, and how they are used in electronics.

 What Capacitors Do

Capacitors are crucial for energy storage, power stability, timing control, and signal coupling in electronic circuits. Their versatility and wide range of applications make them indispensable in modern electronic devices. As such, they play a vital role in electronic circuits for several reasons:

  1. Energy storage: capacitors store electrical energy and release it when needed, making them ideal for applications requiring short bursts of power.
  2. Filtering and smoothing: capacitors can also stabilize power supplies by reducing voltage fluctuations and filtering unwanted noise or ripple.
  3. Timing and oscillation: capacitors are used to control timing intervals and frequency in circuits, enabling precise synchronization of components.
  4. Coupling and Decoupling: lastly, capacitors can transfer AC signals while blocking DC signals, maintaining signal integrity and preventing interference.

How Capacitors Work

Understanding how capacitors function and their construction enables engineers to design and select the appropriate capacitors for different electronic systems.

Capacitors consist of two essential components: conductive plates and an insulating material known as a dielectric. The conductive plates are typically made of metal, such as aluminum or tantalum, and are placed parallel to each other. These plates act as electrodes for storing electric charge. The space between the plates is where the dielectric material is positioned.

The dielectric material, often made of ceramic, plastic, or electrolytic material, acts as an insulator, preventing direct flow of current between the plates. However, it allows an electric field to form across it.

When a voltage is applied to the capacitor, electrons gather on one plate, while the other plate becomes positively charged. This charge separation creates an electric field in the dielectric material, storing electrical energy.

Capacitors store this energy temporarily, and when the voltage across the capacitor is removed or changed, they release the stored energy. The release of energy can be instantaneous or gradual, depending on the circuit configuration and the capacitor's properties.

The capacitance value determines how much charge a capacitor can store for a given voltage. Capacitance is measured in Farads (F), although most capacitors used in electronic circuits have values in microfarads (μF), nanofarads (nF), or picofarads (pF).

Capacitors are built by sandwiching the dielectric material between the conductive plates. The assembly is then enclosed in a protective casing, which also acts as an insulator to prevent accidental contact. The size and type of capacitor depend on the application, with different dielectric materials and construction methods used to meet specific requirements.

Types of Capacitors

Capacitors come in various types, each with its own unique characteristics and applications. In this article, we will briefly cover six popular types of capacitors: electrolytic, ceramic, film, tantalum, silver mica and supercapacitors.

  1. Electrolytic Capacitors

Electrolytic capacitors are polarized capacitors known for their high capacitance values. They are constructed using an electrolyte-soaked paper as the dielectric and consist of two plates—an anode (positive) and a cathode (negative). These capacitors are primarily used in applications that require large capacitance values, such as power supply filters and audio amplifiers. However, it's important to note that electrolytic capacitors have polarity, and connecting them incorrectly can lead to failure or even explosion.

  1. Ceramic Capacitors

Ceramic capacitors are widely used due to their small size, high capacitance, and low cost. They utilize a ceramic material as the dielectric and contain two metal plates. Ceramic capacitors are available in various types, including multilayer ceramic capacitors (MLCCs) and ceramic disc capacitors. They find applications in a wide range of electronic devices, from consumer electronics to telecommunications equipment. MLCCs are especially popular for their high capacitance values and stability over a broad temperature range.

  1. Film Capacitors

Film capacitors employ a thin plastic film as the dielectric material. They are known for their excellent electrical properties, reliability, and low tolerance. Film capacitors come in different variations, such as polyester (Mylar), polypropylene (PP), and polyethylene terephthalate (PET). These capacitors are often used in audio systems, power factor correction circuits, and motor control applications. Film capacitors are non-polarized, making them suitable for AC applications.

  1. Tantalum Capacitors

Tantalum capacitors are known for their high volumetric efficiency, stable capacitance, and excellent frequency response. They use tantalum oxide as the dielectric material and feature a solid electrolyte. Tantalum capacitors are commonly employed in compact electronic devices, including smartphones, laptops, and digital cameras. They offer high capacitance in a small package size, making them ideal for applications with space constraints. It's worth mentioning that tantalum capacitors are polarized and must be connected correctly to avoid damage.

  1. Silver Mica Capacitors

Silver mica capacitors are widely used in electronic circuits due to their stability, high precision, and reliability. They employ a thin sheet of mica as the dielectric material, which is sandwiched between two metal electrodes, typically made of silver. The silver electrodes are connected to the external leads of the capacitor. One of the key advantages of the silver mica capacitor is its exceptional temperature stability. It exhibits minimal variation in capacitance over a wide range of operating temperatures, making it suitable for applications that require precise and consistent performance.

  1. Supercapacitors

Supercapacitors, also known as ultracapacitors or EDLCs (electric double-layer capacitors), are advanced energy storage devices. They combine electrostatic and electrochemical principles to store energy efficiently. Unlike traditional capacitors, supercapacitors utilize high surface area electrodes and an electrolyte solution. This design allows them to achieve exceptionally high capacitance values, enabling rapid energy storage and release.

Supercapacitors offer multiple advantages, including high power density, fast charging/discharging cycles, and long cycle life. They find applications in transportation (regenerative braking, power shaving), renewable energy (energy capture and release), and consumer electronics (faster charging, extended device longevity).

Capacitor Applications

Capacitors find a wide range of applications in the field of electronics. From energy storage and power supply filtering, to timing and oscillation control, as well as coupling and decoupling functions, capacitors play integral roles in various electronic systems. Choosing the appropriate type of capacitor depends on factors such as capacitance requirements, voltage ratings, size constraints, and environmental conditions. Here is a breakdown of essential applications of different capacitor types.

  • Energy Storage

Capacitors are widely used for energy storage in various applications. They can store electrical energy and release it when needed. In devices like cameras, flash units, and electric vehicles, capacitors are used to provide quick bursts of power. Additionally, capacitors play a vital role in energy harvesting systems, where they accumulate energy from renewable sources, such as solar panels or wind turbines. Capacitors’ ability to charge and discharge rapidly makes them suitable for applications that require short-term energy storage and quick power delivery.

  • Power Supply Filters

Power supply filters are crucial for ensuring clean and stable DC power to electronic circuits. Thus, capacitors have become an essential component in power supply filters, as they help reduce noise, ripple, and voltage fluctuations. By strategically placing capacitors in the power supply circuit, they can smooth out the voltage waveform, filtering out unwanted AC components and providing a steady DC voltage. Electrolytic capacitors, with their high capacitance values, are commonly used for this purpose due to their ability to store larger amounts of charge.

  • Timing and Oscillation

 Capacitors are often utilized in timing and oscillation circuits. In combination with resistors, they can control the timing intervals and frequencies of signals in electronic devices. Timing circuits are commonly found in applications such as timers, oscillators, and pulse generators. By adjusting the values of resistors and capacitors, precise timing intervals and oscillation frequencies can be achieved. Ceramic capacitors, with their stability over a wide temperature range, are frequently employed in timing and oscillation circuits.

  • Coupling and Decoupling

Capacitors are extensively used for coupling and decoupling purposes in electronic circuits. In coupling applications, capacitors enable the transmission of AC signals while blocking DC components. They are used to connect different stages of amplifiers, allowing the AC signal to pass from one stage to another, while maintaining DC isolation. Capacitors also play a crucial role in decoupling, where they provide a stable source of local power to sensitive components. By placing capacitors near integrated circuits or microcontrollers, they help to smooth out voltage fluctuations caused by sudden changes in current demand.

Choosing the Right Capacitor

Choosing the right capacitor involves considering multiple criteria, such as capacitance, voltage rating, temperature and environmental considerations, size and package type, frequency response, and cost. By carefully evaluating these factors and understanding the requirements of your specific application, you can select a capacitor that meets your performance, reliability, and budgetary needs. Working closely with component suppliers or consulting engineering resources can provide valuable insights and guidance to ensure an optimal capacitor selection for your project.

The capacitance value is one of the primary criteria to consider when selecting a capacitor. Capacitance is measured in farads (F) or its subunits, such as microfarads (μF) and picofarads (pF). It determines the amount of charge the capacitor can store and influences its energy storage capabilities. When choosing a capacitor, make sure it has a capacitance value suitable for your intended application. Consider factors like the required energy storage, filtering needs, and timing requirements.

Moreover, it is crucial to select a capacitor with a voltage rating that exceeds the maximum voltage expected in your circuit. Operating a capacitor above its voltage rating can lead to performance issues or even catastrophic failure. Capacitors have voltage ratings that indicate the maximum voltage they can withstand without experiencing breakdown or failure. Always consider safety margins and potential voltage spikes when choosing the appropriate voltage rating for your capacitor.

You should also keep in mind that capacitors can be sensitive to temperature variations and environmental conditions. It is essential to evaluate the temperature range in which the capacitor will operate reliably. Some capacitors, such as ceramic ones, have a wider temperature range, while others may have specific temperature limitations. Additionally, consider factors like humidity, vibration, and exposure to chemicals or contaminants that could affect the capacitor's performance and durability.

The physical dimensions and package type of a capacitor are also important considerations, especially when dealing with space-constrained applications. Capacitors are available in various package types, such as through-hole, surface mount, or specialized packages. It is recommended to first assess the available space on your PCB (Printed Circuit Board) and choose a capacitor that fits the size requirements without compromising performance or functionality.

Don’t forget that different types of capacitors exhibit varying frequency responses. Some capacitors, like ceramic capacitors, have excellent high-frequency characteristics, making them suitable for applications involving rapid changes in voltage or AC signals. On the other hand, film capacitors may be preferred for applications that require stable performance across a broad frequency range. Consider the frequency response requirements of your circuit to ensure the chosen capacitor is suitable for the intended application.

Lastly, cost is an important factor when selecting capacitors, especially when working with budget constraints or high-volume production. Capacitors come in a wide range of prices depending on their type, capacitance, voltage rating, and other specifications. Evaluate your project's budget and balance the desired capacitor specifications with the available funds.


As technology continues to evolve, capacitors will continue to play a vital role in enabling innovative electronic advancements. By staying informed about the latest capacitor technologies, applications, and best practices, engineers and designers can unlock the full potential of capacitors and create innovative electronic solutions that shape the future.

So, whether you're designing a complex electronic system or tinkering with a small DIY project, capacitors will always remain indispensable components, silently supporting the world of electronics with their remarkable capabilities. 

FastCap® Ultracapacitors is a division of Nanoramic®, a company that specializes in advanced material solutions based on nano-carbons. Nanoramic’s® advanced materials solutions are enabling for a number of energy storage technologies including high performance ultracapacitors, which rely on nanocarbon-based electrodes.

FastCap® Ultracapacitors is an industry leader in harsh environment energy storage, producing the only ultracapacitors capable of operating in temperatures up to 150C and under conditions of high shock and vibration.

At Fastcap, our ultracapacitors are designed with a focus on longevity, cost-effectiveness, exceptional power and energy density, safety, and fast-charging capabilities. What's more, they can handle even the harshest conditions, including extreme temperatures and vibrations. With such features, FastCap® Ultracapacitors are the perfect solution for various industries, including electric vehicles/mobility, defense, aerospace, lasers, IoT, energy exploration, and beyond. Get in touch with us today and unleash the power of your operations!

 If you need to add to your platforms the superior benefits of FastCAP Ultracapacitors, click here and get in contact with us.

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