Within the field of consumer electronics, there are various types of components used in electronic circuits for many applications and one of the most common passive components which exists in almost every device is the capacitor. Invented around 260 years ago by a scientist in Germany, the capacitor was used as a device that functions to store potential energy, which is basically an electrical charge, electrostatically. Unlike batteries, which stores its charge as chemical energy, capacitors charge and discharge fairly rapidly in a magnetic field with the use of two parallel conductive plates separated by a dielectric. Originally built by Dutch professor Pieter van Musschenbroek, the Leyden jar is famously known to be the first-ever capacitor, simply composing of a simple glass jar partially filled with water and aluminum foil inside. The glass jar acts as the insulator for the two conductors, which is the aluminum foil, while a metal chain is hung inside the jar connected to a brass rod located above the jar cover. From there, a grounding source will be applied and this all essentially makes up the basics of a capacitor. To charge the Leyden jar, voltage is simply applied to the jar and to the brass rod which discharges in the same manner as well. Now, in terms of the different types of capacitors, they all have the same function, which is to store energy to be able to use later but they come in various forms and packages that will be explained below.
These are one of the most common capacitors which can range from a variety of capacitance values, used for countless applications. With two metal film plates as conductors and electrodes, a semi-liquid electrolyte solution serves as the dielectric. Most of the time, electrolytic capacitors are polarized and are indicated by markings to indicate the right polarity when applying voltage. From smoothing operations to simple timing circuits, electrolytic capacitors can come in both aluminum or tantalum forms, which can be found in almost any device.
Another common polarized capacitor is the film capacitor and as the dielectric, a very thin plastic film is used which can vary from polyester film, polystyrene film, polypropylene film, and many others. The main difference between film capacitors and any others is the film dielectric which can take shape in many physical forms depending on the purpose. Film capacitors which have the polypropylene film are most commonly used for high-frequency, high-power uses, especially when dealing with AC voltage and inductive heating but can be used for many other applications.
One of the unique polarized capacitors is the mica capacitor, where instead of air or plastic being used as the dielectric, mica is used. If you didn’t know before, mica refers to a group of natural minerals and when you hear the name “silver mica capacitor” or “damped mica capacitor”, it refers to the mica being covered by metal plates of that specific material to produce the desired capacitance value. As a finishing touch, mica capacitors are normally epoxy-coated to protect the internal parts from the exterior environment. In regards to applications for mica capacitors, due to its high-level performance accuracy, it can be used in filters, transmitters, radios, TV amplifiers, etc.
One capacitor which you may not have seen around so often is the paper capacitor, which construction is extremely simple to understand. It uses two aluminum foil sheets as conductors while its dielectric is composed of paper, which may be oiled or waxed. After that, paper capacitors are often rolled into the shape of a cylinder with a plastic-coated capsule. The package of a paper capacitor is different from others as its legs come out horizontally, rather than vertically. A unique aspect of a paper capacitor is that it has a low resistance path to AC voltage and a high resistance path to DC voltage so, therefore, it is best used in an AC circuit application or any high voltage/current application.
The last type of capacitor is the ceramic capacitor and it differs from the rest as it is a non-polarized component, meaning that there is no specific input for your positive and negative leads. As said in the name, these capacitors use a ceramic material as their dielectric and can come in two types: multilayer ceramic capacitors or ceramic disc capacitors. For surface mount projects which are typically smaller in size, multilayer ceramic capacitors work fabulously with smaller capacitor values normally. However, with through-hole projects, ceramic disc capacitors are the ones that are widely known to be used. Speaking about projects, I would highly recommend utilizing Seeed OPL if you require any electronic components for your projects as they have an incredible variety of parts in their library at your disposal, covering almost all capacitors types. After that, if you wish, you can also manufacture and assemble your project into a PCB with Seeed PCB Assembly as the parts chosen from the OPL can then be used on your PCB with a few clicks of a button. Their service is completely effortless and affordable for customers like you and I would really recommend checking them out if you haven’t done so already.
Anyways, with ceramic capacitors, they have a very low maximum-rated voltage and are non-polarized, so connecting an AC source to these capacitors aren’t an issue. Furthermore, ceramic capacitors are known to have an amazing frequency response because of low parasitic effects like resistance or inductance, making it ideal for almost any application.
To sum up, capacitors in the electronic field have an important purpose and role in many circuits with their wide variety to suit your particular requirements. They all have their own, individual aspect with what they are best suited for, so if you are wanting to choose a specific capacitor for your project, make sure to choose wisely while considering all your other possible options. However, you will find yourself using a lot of electrolytic, film and ceramic capacitors mainly when creating projects as those are the most common capacitors for general applications and are quite cheap to purchase. But you may stumble upon mica capacitors or even paper capacitors when diving into more specialized applications so make sure you always know what you are working with, its general specifications and how you should use it correctly.