Types of Capacitors

Capacitors are one of the most used and useful electronic component used in any modern electronic and electrical circuit and devices.
Capacitors have a long history or production and usage, with more than 250 years of history capacitors are one of the oldest electronic component being studied, designed developed and used. Thus with a long history of development Capacitors have a lot of types based on various factors.
For the scope of this article we will not be able to cover all the types and classifications of capacitors but we will discuss about the most popular and most used types of capacitors.

Types of capacitors based on Construction:

Based on the arrangement of the plates and dielectric in a capacitor or based on the construction of capacitor capacitors are classified into following types:

1. Spherical Capacitors:

Spherical capacitors are those kinds of capacitors which are build up of concentric Spherical Plates with dielectric in between them , read more on Spherical Capacitors here: https://electronicspani.com/spherical-capacitor/

2. Parallel Plate Capacitors:

Parallel plate capacitors are those types of capacitors which are built using parallel plates separated by a distance with dielecetric in between them, read more on parallel plate capacitors here: https://electronicspani.com/parallel-plate-capacitor/

3. Cylindrical Capacitors:

Cylindrical capacitors are  build up of cylindrical plates with dielectric in between the two cylindrical plates, read more on parallel plate capacitors here: https://electronicspani.com/cylindrical-capacitor/

Types of Capacitors based on construction
Types of Capacitors based on construction

Types of Capacitors based on General Classification:

Based on the general classification types, capacitors are classified into following two types:

1. Fixed Capacitors

The capacitors whose value is fixed during the manufacturing process and cannot be latter altered is called fixed capacitor. Fixed capacitors are also further classified into two kinds, Electrolytic and Non-Electrolytic capacitors:

a. Non-Electrolytic Capacitor:

Non-Electrolytic capacitors are those capacitors which does not use a electrolyte in it’s construction. Non-electrolytic capacitors can also be classified into following types:

i. Paper Capacitor:

A paper capacitor is constructed of two thin tinfoil sheets which are separated by thin waxed & oiled paper or plastic, the sandwich of thin foils and paper or plastic is then rolled  into a cylindrical shape which is then enclosed in plastic capsule. The two tin foils of the capacitors are attached to two external leads.

These capacitors were called paper capacitors because initially paper was used in between the two foils of the capacitor, but these days other materials like plastic are also used.

Paper Capacitor
Paper Capacitor

The capacitance of paper capacitor can range in between 0.001 to 2.000 Micro farad and the voltage rating can be as high as 2000 Voltage.

ii. Mica Capacitor:

To construct a mica capacitor several thin plate of metal are sandwiched separated by thin sheets of mica,  the alternate plate are then connected to form two terminals which are connected to two leads and the whole assembly is enclosed in plastic of bakelite capsule. Mica capacitors have small capacitance in the range of 50-500 picofarads , but have relatively high working voltage of up to 500 voltage.

Mica Capacitors
Mica Capacitors

iii. Ceramic Capacitor:

To construct a Ceramic capacitor a hollow tubular or plate like ceramic material such as titanium dioxide and barium titanate is taken , which is then coated  by a deposit of silver compound on both inner and outer surface of the ceramic, the two silver coating acts as two plates and the ceramic material acts as dielectric. The two surfaces are then connected to leads and the whole assembly is then encapsulated in a moisture proof coating.

Ceramic Capacitors
Ceramic Capacitors

Because of very high dielectric constant of ceramics ; Ceramic capacitors have very high capacitance of up to 0.01 micro farad as compared to their size.

b. Electrolytic Capacitor:

Electrolytic capacitor is a capacitor which use an electrolyte as negative plate. Electrolyte capacitors have positive and negative plate and consists of following materials:
a. A positive plate made up of Aluminium

b. An extremely thin insulating film of Aluminium oxide as dielectric which is electrochemically deposited deposited in the surface of positive Aluminium plate itself.

c.  An electrolyte of borax or carbon salt which is absorbed by a absorbent gauze  which is placed in contact with the dielectric and connected to an external Aluminium lead acting as negative lead.

Electrolytic Capacitor
Electrolytic Capacitor

A electrolytic capacitor is made as described below:

A very thin and long stripe of Aluminium is coated with a very thin layer of Aluminium oxide by electrochemical process, which is then covered with a layer of gauze saturated with electrolyte of borax or carbon salt , then to the another side of the gauze is placed similar very thin and long stripe of Aluminium, the two Aluminium stripes are then connected to Aluminium leads  and the entire sandwich is then rolled up to form a cylinder and  placed inside a cylindrical metal casing.

Because of the extremely thin distance of electrolyte between the positive Aluminium plate and the negative electrolyte , electrolytic capacitors have very large capacitance compared to their size which can range from 1 – 10000 microFarads.

Electrolyte capacitors are polarized , or they contain positive and negative leads ,  so they must be connected in an electronic circuit correspondingly. If a electrolytic capacitor is connected in reverse polarity in circuits it results in short circuiting , over heating and also gassing which might even cause the capacitor to explode.

2. Variable Capacitors

A variable capacitor is the capacitor whose capacitance can be varied as required usually by rotating a shaft attached to the capacitor.

A normal variable capacitor consists of a Multi Plate parallel plate capacitor where one set of plates is stationary which is called stator  while the other sets of plates is rotatable and is connected to a shaft, and by rotating the shaft the two sets of plates can be configured to come over each other in a required amount which determines the capacitance of the capacitor, when the sets of plates are fully over each other the capacitance is highest .

Variable Capacitor
Variable Capacitor

When two or more capacitors are connected to a common shaft the configuration is known as a ganged capacitor; ganged capacitors is normally used with short wave radio equipment.

Ganged Capacitor
Ganged Capacitor

Variable capacitors can also be made with with two small flexible metal plates separated by air, mica or ceramic slab as dielectric. the spacing between the plates can be changed by a means of screw , this kind of variable capacitors are usually small in size and are called trimmer. They are normally used in circuits for small adjustments orr fine tuning.

Trimmer Capacitor
Trimmer Capacitor