Types of Capacitors: Explanation and Symbols

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Types of capacitors are made based on their:

Lengths,
Forms,
Styles,
Materials, and
Applications or purposes.

Capacitors have a long history in electrical and electronic circuits. They have been discovered and used for more than 250 years. Capacitors can be considered as the oldest electronic components we use, study, and design until now. Along with the time, capacitors have different types for different applications and functions.

In this post we will learn all about capacitors, especially their types, functions, and symbols we may use in the future. The types of capacitors we listed below are the most common to be used in wide applications.

Keep in mind that a capacitor is an electronic component which is able to store energy in the electrical charge form. You can say it is quite similar to a battery to some degree.

What is Capacitor?

Along with resistor and inductor, a capacitor is a passive electrical element and temporarily able to store energy in the form of electrical charge.

Look at the common symbol of capacitor below:

We still don’t know what type of capacitor above, but it still represents the structure of a capacitor.

A capacitor is made from a pair of conductors, separated from each other by a dielectric material. When a capacitor is connected to a power source, one plate will accumulate positive charge while the other one will accumulate negative charge.

For short,

A capacitor is made from a pair of electrical conductors (plates), separated by an insulating layer (dielectric).

A capacitor is mainly used to provide capacitance in the circuit. We will discuss “what is a capacitance” immediately below.

The common purposes for small-sized capacitors are:

Couple signals (in an amplifier),
Electric filters,
Tuning circuit, and
Improve performance on power supply systems (rectified voltage or current).

The common purposes for large-sized capacitors are:

Power factor correction in AC power distribution and transmission systems,
Strobe lights for electric motors.

What is Capacitance

Capacitance is the ability of a capacitor to store energy in the form of an electrical charge. Using mathematical equation:

$\begin{align*}C=\frac{q}{V}\end{align*}$

where:
C = capacitance, measured in Farad (F)
q = electrical charge, measured in Coulombs (C)
V = voltage, measured in volt (V)

From the equation above we can conclude that:

Capacitance is the ratio between electrical charge (q) and voltage (V).

Types of Capacitors and Symbols

There are quite a number of types of capacitors we can use in our circuit design. It can be very popular or very rare to use. Anyway, observe the capacitor types and symbols listed below along with their explanations.

Ceramic capacitor,
Mica capacitor,
Non-polarized capacitor,
Electrolytic capacitor,
Paper capacitor,
Film capacitor,
Power film capacitor,
Supercapacitor, and
Variable capacitor.

Ceramic Capacitor

Ceramic capacitors don’t have polarity and are constructed from two or more ceramic layers as dielectric and metals as the electrodes.

From the name implies, ceramic capacitor is made from ceramic material as its dielectric layer. This ceramic acts as an insulator to isolate the pair of electric conductors.

Ceramic capacitor is constructed from:

Protective coating
Ceramic disc (dielectric)
Electrode
Connecting wire terminal

Ceramic materials can be divided further based on their stability:

Class 1: have high stability and low losses. This class is able to compensate for the temperature effect on a resonant circuit application. Its IEC codes are C0G/NP0, P2G/N150, R2G/N220, U2J/N750 etc.
Class 2: have high volumetric efficiency. Commonly used as buffer, coupling, and bypass. Its IEC codes are X7R/2XI, Z5U/E26, Y5V/2F4, X7S/2C1, etc.

Reading the explanation above will conclude that with the plasticity of ceramic materials, we can make different styles such as:

Multi-layer ceramic capacitor (MLCC) for SMD mounting,
Ceramic X2Y as decoupling capacitor,
Ceramic EMI as suppression capacitor for power supply safety connection, and
High voltage power capacitor.

An MLCC is constructed by surface mounted technology and has smaller size, thus widely used in many applications. This capacitor has capacitance values ranging between 1 nF and 1uF. It even has 100uF capacitance but it is not commonly used.

Multilayer capacitor has mostly alternating layers and produces a single capacitor with characteristics:

Increased capacitance,
Decreased losses, and
Decreased parasitic inductances.

Ceramic disc capacitor uses silver contact terminals for both sides and is made from multiple layers. This construction can produce larger capacitance and have high frequency responses.

Overall, ceramic capacitors are well-used for high current and high frequency pulse loads.

Mica Capacitor

Mica capacitor is also categorized as a natural mineral and doesn’t have polarity. We can find different types of mica capacitor:

Silver mica capacitor
Clamped capacitor

Silver mica capacitors use a dielectric. This capacitor is made from mica sheet sandwich, coated by metal for both sides and encased in epoxy to maintain the environment. This capacitor is stable and reliable even with its small size.

On the other hand, clamped capacitors are obsolete because they have worse characteristics than silver mica capacitors.

This capacitor has characteristics:

Chemically stable
Electrically stable
Mechanically stable
Low power loss

It uses special structure binding to make layered structure, Muscovite and phlogopite mica are the most common.

Muscovite mica has better electrical characteristics but the other mica has higher temperature resistance.

Non-Polarized Capacitor

As its name implies, this resistor doesn’t have polarity. This capacitor can be divided further into plastic foil and electrolytic.

The plastic foil has its non-polarized characteristic made by nature.

On the other hand, electrolytic capacitors are man-made. This capacitor is constructed from two capacitors connected in series back-to-back. This results in a non-polarized capacitor with half capacitance.

This type of capacitor is commonly found on filter and power factor correction circuits.

Electrolytic Capacitor

This capacitor is different from others, because we need to take caution of its polarity. This capacitor is constructed by:

The first electrode is made from a thin metal film layer.
The second electrode is made from a semi-liquid electrolyte solution (jelly or paste).
The dielectric anode plate is made from a thin layer of oxide, constructed from an electrochemical process with less than ten microns thickness.

This is one of the types of capacitors that are mostly produced with polarity.

Its insulating layer is very thin hence it can be produced with high capacitance with small size and the gap between two plates is also very small.

Because of the presence of the polarity, it needs to be connected to the DC circuit (majorly) and of course it has to be connected properly.

Connecting positive electrode to negative terminal or connecting negative electrode to positive terminal will break the capacitor. This breaks the capacitor because the insulating oxide layer is broken and the damage is permanent.

If you are wondering which is the negative electrode, the strip indicates which is the negative electrode and the other one is positive.

Electrolytic capacitor is mainly used for power supply circuits because of its large capacitance and being able to eliminate small voltage ripple. Its application is mainly for coupling and decoupling.

We can categorize electrolytic capacitor further based on its materials:

Niobium electrolytic capacitor with niobium pentoxide as dielectric,
Aluminium electrolytic capacitor with aluminium oxide as dielectric, and
Tantalum electrolytic capacitor with tantalum pentoxide as dielectric.

Electrolytic material and composition affect the conductivity of the anode:

Non solid (liquid, wet): has lowest cost with conductivity about 100 mS/cm,
Solid manganese oxide: has high stability and quality, conductivity about 100 mS/cm, and
Solid conductive polymer (Polypyrrole): ESR value less than 10 mΩ, conductivity about 100 – 500 S/cm.

The disadvantages of using an electrolytic capacitor is its low voltage rating.

Paper Capacitor

Paper capacitors belong to the non-polarized capacitor group.

Just as you imagine, this capacitor uses “paper” in it. More accurately, this capacitor is built from a paper (or oiled paper) and thin wax that separate two tin foil sheets.

These foils and papers are rolled together into cylindrical shape and coated by a plastic capsule. The two foils are connected to an external load or circuit.

Paper capacitor’s capacitance ranges from 0.001 to 2 uF and its voltage rating is surprisingly high up to 2000V.

Film Capacitor

Film capacitor is a non-polarized capacitor, using an insulating plastic film as its dielectric layer.

Film capacitor utilises a thin plastic as its dielectric zone. It is constructed with a very thin layer with complicated film drawing procedure. It is complicated because its environment can affect the film when manufactured. Electrodes are added to protect the environment’s effect.

Electrodes can be made from metallized aluminium or zinc and added to the both sides of plastic film.

The film material can be divided further into:

Polylester
Metallized
Polypropylene
PTE
Polystyrene

For its core needs to be selected properly looking at its property and characteristic.

Film capacitor has advantages on its:

Stability
Reduced equivalent series inductance (ESL), low ohmic losses
Reduced equivalent series resistance (ESR), low parasitic inductance
Low cost

Using PTE film will improve its heat resistance and is commonly used for military technology. Using polyester film will improve its stability.

Film capacitor is well-used as snubber circuit (high surge current), AC power circuits, and high frequency applications.

Power Film Capacitor

Power film capacitor is similar to the film capacitor we read before, but it is more suitable for high power applications where film capacitor is not suited for it.

While a film capacitor is mainly used for electrical, electronic, and mechanical purposes, the power film capacitor is focused on safety of equipment and personnel.

In the modern literature, electrical and electronic are often assumed as “one” thing, this is not absolutely true. Keep in mind that the boundary that keeps electrical from electronic is the power rating. The power film capacitor is well-suited for electrical application with reactive power 200 Volt-Ampere where the film capacitor is much lower.

Power film capacitor mainly uses polypropylene film as its dielectric layer. Other than this, we will find metallized paper capacitor (MP capacitor) and mixed dielectric film capacitor with polypropylene dielectric.

Power film capacitor is efficient for converters (voltage, current, or frequency), storing and delivering electrical energy to improve the power factor.

Power film capacitor has a voltage rating about 120 V AC to 100 kV AC.

There are several applications for power film capacitor:

AC power factor correction,
Electrical installation and plants,
Energy storage power film capacitor banks, and
Substation capacitor bank.

Supercapacitor

Supercapacitor is still in the electrochemical capacitor family. It is also called an ultracapacitor sometimes.

This supercapacitor is an electric double layer capacitor (ELDC), pseudocapacitors, or hybrid capacitors. Unlike the other types, this capacitor doesn’t have solid dielectric.

Its capacitance value is determined by its storage principle:

Electric double layer capacitor (ELDC): its storage ability comes from the charge separation process in a Helmholtz double layer at the interface between the surface of the conductor and the electrolyte solution.
Pseudocapacitor: its storage ability comes from redox reactions, electrosorption, or intercalation on the surface of the electrode.

Supercapacitors is divided further based on their electrodes design:

Double layer capacitors: carbon electrodes.
Pseudocapacitors: electrodes of metal oxides or conducting polymers.
Hybrid capacitors: special and asymmetric electrodes which show significant double layer capacitance and pseudocapacitance.

Supercapacitor is not commonly used for general purpose so you may leave this explanation already. If you have interest in learning and using this type of capacitor then you can read the journals about this.

Variable Capacitor

Just like resistors and inductors, we also have variable capacitors to fulfill our needs for special purposes. This variable capacitor is also tuned mechanical motion.

We have two types of variable capacitors:

Tuning capacitor: this variable capacitor is used to tune oscillator circuits on radio and similar devices.
Trimmer capacitor: this one is similar to potentiometer, used as one-time oscillator circuit internal adjustment.

How do variable capacitors work?

We can adjust the distance between the plates mechanically or adjust the plate surface area amount which overlaps. They mostly use air as their dielectric layer.

Closing Remark

And this is the end of the explanation about the types of capacitors. You may find different numbers from this explanation, but here we have listed the most commonly used in electrical purposes.

Hope this can help you on learning the types of capacitors and help you to decide which one you should use.