Types of Capacitor

Capacitor is an electric component that is used to store electrical charges in an electric field. There are many applications of capacitors; they serve as couplers in electronic circuits, as AC/DC blockers preventing the direct current while the alternating one is let through, as filters for getting rid of interference, and as smoothers for correcting sharp fluctuations in power supplies, and as tuners which set radios on the desired frequency and so on.

There is a large variety of capacitors with respect to their physical dimensions and also with respect to the parameters that characterize electric field energy storage in them. Some of the categories of capacitors include the ceramic capacitors, electrolytic capacitors, Film capacitors and super capacitors. It is necessary to understand that each type has several benefits and drawbacks, which define the possibility of the type’s use in particular applications. This article is aimed to reveal the overview of the main types of capacitors, internal construction, parameters, and applications of capacitors.

What is a Capacitor?

A capacitor is an electrical component which is constructed from two parallel conductors or plates that are separated by an insulating material called dielectric. When a voltage is applied across the plates, the charges of opposite polarity are collected on the two plates while charges of equal magnitudes but opposite polarity are collected on both the plates respectively hence creating electric field in the dielectric. This is defined as the capacitance and possesses the unit of farads, and depends on the area of the plates, the distance between them and the dielectric constant of the dielectric used

Components

The basic components of a capacitor are:The basic components of a capacitor are:

• Dielectric: Distance between plates like air, vacuum, paper, mica, ceramic, plastic film etc as the insulating material help in building an electric field but offer little or no conduction between the plates.
• Plates/Conductors: These include thin metal foil sheets that are used for holding of electric charge when voltage is applied. Some of the materials used for SMD components are aluminum, tantalum, silver, nickel, etc.
• Leads: These are the leads that are used to connect the capacitor to the circuit and these leads are usually externally located.
• Enclosure: Housings also offers internal protection and electrical and thermal barrier to the internal parts of the device. It can also be cylindrical, rectangular, or disc shaped.

Types of Capacitors

Capacitors are electronic devices that are used to retain electrical charges for some time. There are many different types of capacitors, but they can be broadly grouped into two main categories: popular types are fixed value capacitors and variable capacitors.

Fixed Value Capacitors

Ceramic Capacitors:

• Ceramic capacitors are made up of ceramic materials like the titanium dioxide. They offer low cost, compact size, high frequency response and are efficient at high temperature.
• However, their capacitance value is not fixed and they are generally lower in capacitance than other varistors. For instance, it can be used in bypassing and coupling.

Electrolytic Capacitors:

• Electrolytic capacitors consist of one of the plates that has an electrolyte (an ionic conducting liquid) to get far more capacitance for the same volume. They are also polarized, that is, they can only function if a DC voltage is applied across their terminals in one given orientation.
• They are useful in applications with high capacitance ratings and used for energy storage. The main disadvantages of the two are their large dimensions, limited durability and relatively weak high frequency extension.

Tantalum Capacitors:

• Tantalum capacitor is the electrolytic capacitor that employs tantalum metal for its anode or positive terminal. Tantalum capacitors provide better high-frequency response than standard electrolytic capacitors, possess lower leakage current and can be built in smaller volume.
• However, they are more expensive than the ordinary type of cars hence they are out of reach to many people. It is used commonly in sample and hold circuits, timing circuits and in audio equipment.

Plastic Film Capacitors:

• These capacitors are constructed from plastic film with layers of metal deposited on each side of the film. The capacitance is also very high with low inductance, and the capacitance does not degrade under time or frequency and they can handle high temperatures very well.
• It has disadvantages that are mainly associated with their size and slightly higher cost as compared to other similar products. Some of the common application are bypassing, coupling, and power conditioning.

Variable Capacitors

Trimmer Capacitors:

• Smaller capacitors with variable settings are referred to as trimmer capacitors and are used to make minor adjustments to circuits.
• These are fixed in small cases with head screws in such a way that the capacitance can be adjusted by turning the screw head with the help of a screw driver. It helps the capacitance to be tuned during the design and testing phase of a particular device.

Tuning Capacitors:

• Tuning capacitors are those capacitors which can be changed and are used for tuning the frequency circuits in instruments like radio. The plates rotate and this changes the overlapping area by altering the capacitance.For it enables the getting of a circuit with certain parameters of capacitance without having to use fixed capacitors to switch in and out of a circuit.

Differences or Comparisons

• Ceramic vs. Electrolytic: Ceramic capacitors are more stable and suitable for high-frequency applications, whereas electrolytic capacitors offer higher capacitance values in a smaller size.
• Film vs. Mica: Film capacitors are versatile and used in various applications, while mica capacitors are specialized for high-precision tasks.
• Supercapacitors vs. Traditional Capacitors: Supercapacitors have much higher energy density but lower voltage ratings.

Characteristics of Capacitors

The important characteristics to consider while selecting a capacitor are:The important characteristics to consider while selecting a capacitor are:

• Capacitance Value: Farads or even more often micro or pico farads
• Tolerance: Tolerance in terms of deviation from the stated capacitance value
• Voltage Rating: The maximum voltage that can be applied to the circuit whether in direct current or in an alternating current without causing damage to the devices.
• Temperature Coefficient: This capacitance change with temperature is as a result of the change in capacitance value with temperature.
• Frequency Response: It means the actual capacitance that the component provides over a given frequency band.
• Leakage Current: Very small current that flows through the circuit even if no voltage is being supplied across it.
• Equivalent Series Resistance (ESR): Resistance through the wires and other components of the circuit that leads to power loss
  
  

Examples of Capacitors

1. 100nF Multi-layer Ceramic Capacitor: Used often in high frequency bypassing and coupling purposes. Provides a low ESR and inductance.

2. 10μF, 450V Aluminum Electrolytic Capacitor: Used in forward converters and voltage doublers as well as in smoothing circuits for power supplies. Unpolarized version works as an acoustical coupling capacitor.

3. 5.5V, 100F Supercapacitor module: Applied in the circuits in order to deliver high current pulses. It can be fast recharged in several seconds and survive millions of duty cycle.

4. 365pF Variable Air Capacitor: Used for aligning in radio receivers. It enables selection over the entire AM or FM broadcasting bands.

Advantages of Capacitors

• It has a fast its stores and releases energy quickly.
• It is designed to shield or block DC signals while passing AC signals.
• Practices undesired signals such as in power supplies and communication paths
• Adjusts and synchronizes frequencies through radio frequency (RF) circuitry
• This isolates or disconnects various steps of the amplifier circuits in couples and decouples.
• Mainly employed in applications such as backup energy sources for example in supercapacitors.

Disadvantages of Capacitors

• Can never store as much energy like batteries do.
• Aluminum and tantalum electrolytic and ceramic capacitors are self-healing but have a finite lifespan.
• Compared to batteries, supercapacitors discharge themselves more rapidly because they have a higher leakage current.
• The capacitor is used that can change its capacity and they can wear out due to time and frequent usage.
• Large capacitors when charged with electricity can store lethal energy even after the power is switched off.

Applications

• Voting and filtering power supplies
• Generating timing and pulse signals
• Designing and optimizing the circuits on the RF signals
• An audio crossover is a type of passive system that separates incoming audio signals into different frequency bands that can then be processed separately by other equipment, such as equalizers.
• In rods for voltage control of inductive loads, snubbers are used to reduce voltage peaks.
• Circuitry back-up power supplies for memory elements

Conclusion

It is worth pointing out that capacitors are one of the most crucial elements of practically any electronic systems in use today. They temporarily hold electric charge between conductors which make useful functions like filtering ac signals, supplying bypassing noise supply, setting time constants, oscillators and as backup to batteries. As the capacitance density is further investigated for improvements using nanomaterials, they will remain central to the development of future instruments.

Types of Capacitor - FAQs

Why capacitors are used more than inductors in practical circuits?

Inductors, on the other hand, can easily be apart from ceramic, plastic films and electrolytes to achieve different capacitance values in small packages. They also cost lower and have improved characteristics at higher frequencies compared to the similar inductors.

The working lifetime of capacitors is determined in what way?

PR capacitor lifetime is defined in terms of the maximum hours of operation at a given temperature for the specified voltage conditions. Ceramic and film capacitors are ensured for a minimum lifetime of 10000 hours under maximum voltage and temperature conditions.

Positive terminal is denoted by a +ve sign and the negative terminal is denoted by -ve sign, why so?.

Aluminum and tantalum electrolytic capacitors has conducting liquid electrolyte as an electrode which requires correct polarity for preventing short circuiting the dielectric through wrong plate connections. Non-polarized capacitors contain the ceramic and film capacitors, which can be connected in both directions.