What Is a Capacitor?
- A capacitor is an electrical component that stores energy by holding electric charges on two metal surfaces (called plates), which are separated by an insulating material known as a dielectric.
- It was once called a condenser, a term still used in some contexts, like in condenser microphones.
- Capacitors are passive components, meaning they do not create energy but store and release it, as needed.
- They have two connection points, or terminals, and are commonly used in electrical circuits for tasks such as energy storage, filtering, and controlling signal flow.
Symbol Of Capacitor
The conducting plates hold charges Q1 and Q2 (typically, if one plate has a charge of +q, the other plate will have a charge of −q). The electric field between the plates is determined by the amount of charge on them. Since the potential difference (VVV) is directly related to the electric field, we can say:
V∝EV
This implies that as the electric field increases, the potential difference between the plates also rises. Furthermore, the relationship between the charge (q) on the plates and the potential difference (V) is given by:
q=C⋅Vq
where CCC is the capacitance, which indicates the capacitor’s capacity to store charge for a given potential difference. This equation is fundamental in understanding how capacitors operate within circuits.
Types Of Capacitor-
Capacitors can be classified based on their structure into:
- Fixed Capacitors
- Variable Capacitors
They are also categorized into two types based on their polarization:
- Polarized Capacitors
- Non polarized Capacitors
- A polarized capacitor, often referred to as an electrolytic capacitor, is a crucial component in electronic circuits and is known for its ability to provide high capacitance density.
- Non polarized capacitors are preferred in certain applications because they aren’t damaged by reverse voltage and can be used in pure AC circuits.
- They are also used in DC circuits, as they don’t have specific positive and negative terminals.
- These capacitors operate at high frequencies and have low leakage current.
Now, let’s explore the different types of capacitors. Capacitors are divided into two mechanical categories: fixed and variable. Fixed capacitors have a constant capacitance value, while variable capacitors allow for adjustable capacitance. Below is a brief overview of various types of capacitors and their characteristics:
- Ceramic Capacitors
- Film Capacitors
- Mica Capacitors
- Glass Capacitors
- Paper Capacitors
- Electrolytic Capacitors
- Aluminium Electrolytic Capacitor
- Tantalum Electrolytic Capacitor
- Niobium Electrolytic Capacitor
- Super Capacitors
- Pseudo Capacitors
- Electrochemical double-layer Capacitor
- Hybrid Capacitor
Let’s see one by one,
Ceramic Capacitor-
- Ceramic Capacitors are among the most widely used types of capacitors. They utilize a ceramic material as the dielectric, which provides their insulating properties.
- Because ceramic capacitors are non-polar, they can be connected in either direction within a circuit, making them versatile for various applications.
- Their simplicity, reliability, and broad usage in both AC and DC circuits contribute to their popularity.
Application-
- Ceramic capacitors are frequently used in printed circuit boards for high-density applications because of their compact design.
- Their non-polarity makes them versatile for general use in many types of circuits.
- They are also employed in DC motors to minimize RF noise.
- Additionally, ceramic capacitors are utilized in transmitter stations within resonant circuits to aid in signal transmission management.
Film Capacitor-
- Film capacitors, also known as polymer film, plastic film, or film dielectric capacitors, have the benefit of being affordable and possessing an indefinite shelf life.
- They consist of a thin dielectric material, with the other side of the capacitor being metalized. Depending on the application, these capacitors are rolled into thin films.
- Their typical voltage range spans from 50 V to 2 kV, making them versatile for many different applications.
Application
- Film capacitors are widely employed as safety capacitors and to mitigate electromagnetic interference (EMI) in circuits.
- Power film capacitors are commonly used in power electronics systems.
- These capacitors play a key role in protecting devices from unexpected voltage surges.
- They are also used to enhance the power factor of devices, improving their efficiency.
Electrolyte Capacitor-
- An electrolytic capacitor features a metallic anode that is coated with an oxidized layer, which serves as the dielectric.
- These capacitors are polarized, having distinct positive and negative terminals.
- They are also categorized according to the type of dielectric material employed.
Application-
- Electrolytic capacitors are used when a high capacitance is required.
- They serve as filtering devices to reduce ripple voltage.
- In audio amplifiers, they help to minimize electrical noise from the main power supply.
- They are also employed to smooth the input and output signals in DC circuits with a weak AC component.
Paper Capacitor-
- A paper capacitor, often referred to as a fixed capacitor, employs paper as the dielectric material.
- The charge it stores is fixed and unchanging.
- It comprises two metallic plates with paper situated between them, serving as the dielectric.
Application-
- Paper capacitors are utilized in noise filtering, coupling, and decoupling applications.
- They function to block DC signals, enabling AC signals to pass.
- These capacitors are also used in sensors such as those for measuring humidity and fuel levels.
- In car audio systems, paper capacitors help by supplying additional power to the amplifiers.
Pseudocapacitor
- Pseudocapacitance refers to energy storage through fast, reversible electrochemical reactions, enhancing the performance of supercapacitors.
- It offers higher energy density, fast charge/discharge rates, and long cycle life compared to traditional capacitors.
- Materials like transition metal oxides and conducting polymers are commonly used to exhibit pseudocapacitance.
- This technology is ideal for applications such as electric vehicles. It enables rapid charge/discharge cycles and longer battery life in these devices.
Application-
- Pseudocapacitance is used in supercapacitors for efficient energy storage in applications like electric vehicles, renewable energy systems, and portable electronics.
Mica Capacitor
- Mica refers to a group of natural minerals, and mica capacitors are components that utilize mica as their dielectric material.
- There are two primary types of mica capacitors:
- Clamped mica capacitors
- Silver mica capacitors.
- Clamped mica capacitors are largely outdated due to their less desirable performance, with silver mica capacitors being the preferred choice.
- Silver mica capacitors are constructed by layering mica sheets that are coated with silver on both sides to achieve the desired capacitance. The silver coated on the mica acts as electrodes and mica sheets act as dielectric.
Application-
- Mica capacitors are typically chosen for designs that require stable and reliable capacitors with relatively small capacitance values.
- Known for their low loss, mica capacitors are ideal for high-frequency applications and maintain their capacitance over time, ensuring long-term consistency in performance.
Glass Capacitor
- Glass capacitors are constructed using ultra-thin, high-purity glass as the dielectric material.
- The glass offers excellent stability, minimal leakage, and reliable performance across a wide range of frequencies.
- A significant advantage is their ability to function at high temperatures (up to +200°C).
- These capacitors are highly resistant to environmental factors, making them one of the most durable types.
- It provides strong protection against the effects of nuclear radiation.
Application-
- Glass capacitors are used in high-temperature environments, such as industrial equipment and aerospace applications.
- Their resistance to radiation makes them suitable for use in nuclear or space applications.
Niobium capacitor
- Niobium capacitor technology appeared at the market in 2002
- Niobium is similar to tantalum and shares many chemical properties, but has some unique advantages and disadvantages when used in capacitors.
- Niobium capacitors have been around for many years but are limited by factors like lower voltage ratings, less efficient use of space, and compatibility issues with certain materials.
- This technology remains a suitable product in the tantalum capacitor industry, with only a few manufacturers offering it.
- Despite its limitations, niobium capacitors offer benefits such as lower cost, improved safety, and high reliability, making them worth considering in some applications.
Application-
- Niobium electrolytic capacitors are often used as substitutes for tantalum electrolytic capacitors, with similar applications.
- Niobium capacitors are preferred in low voltage applications (3.3 V or 5 V) due to their safer “non-burn” failure mode.
- Unlike niobium capacitors, tantalum capacitors can short circuit when they fail, potentially causing arcs or flames.
- This makes niobium capacitors a safer option in certain electronic designs.
Hybrid Supercapacitor
- Hybrid supercapacitors offer higher operating voltage (up to 3.8 V) and significantly greater capacitance and energy density (up to 10 times more) than symmetric supercapacitors.
- They feature lower self-discharge and standby current, improving overall efficiency.
- Traditional supercapacitors, however, provide higher power capability due to lower ESR, a wider temperature range, and can be safely discharged to zero volts, unlike hybrid supercapacitors.
- Hybrid supercapacitors are similar in construction to traditional ones but use a graphite anode with lithium and a different electrolyte.
Trimmer Variable Capacitor
- Trimmer capacitors are variable capacitors used for initial calibration during manufacturing or servicing, not for end-user adjustments.
- They are typically mounted directly on the PCB, preventing user access, and are set using a small screwdriver during production.
- Trimmer capacitors are more cost-effective than full-sized variable capacitors.
- They are designed for fewer adjustments and are not intended for continuous user interaction.
Application-
- Trimmer capacitors are used in various applications where a capacitance value needs to be fine-tuned during the manufacturing process.
- They are preferred over fixed-value capacitors because other components in the circuit can have tolerances that may vary by as much as 20%.
- Trimmer capacitors help compensate for these variations and ensure the circuit functions as intended.
- Their adjustable nature allows for precise matching of capacitance values in the final product.
Rotary Variable Capacitor
- This type of capacitor adjusts capacitance by rotating the axis to change the position of the conductive plates.
- It is commonly used in radio tuning circuits to fine-tune the received radio frequency.
- By adjusting the plate position, it allows for precise control of capacitance in the circuit.
- This makes it ideal for applications where variable capacitance is needed, such as in radio receivers.
Application-
- Radio communication equipment
- Frequency synthesizer
- Filter circuit
- Oscillator circuit