Types of Capacitors – en

A simple capacitor consists of a pair of parallel plates of area A separated by a small distance d. Often the two plates are rolled into the form of a cylinder with plastic, paper, or other insulator separating the plates. 

In circuit diagrams, a capacitor is represented by either of these symbols:

Types of Capacitors

Capacitors are divided into three basic groups:

• Fixed capacitors. The capacitors whose value is fixed during the manufacturing process and cannot be latter altered are called fixed capacitors. Fixed capacitors are also further classified into two kinds, electrolytic and non-electrolytic capacitors.
• Polarized capacitors. Polarized Capacitors are the ones that have specific positive and negative polarities. While using these capacitors in circuits, it should always be taken care that they are connected in perfect polarities.
• Variable capacitors with a variable capacitance. They are made as trimmers that are typically adjusted only during circuit calibration, and as a device tunable during the operation of the electronic instrument.

The most common group is fixed capacitors. Many are named based on the type of dielectric. For a systematic classification, these characteristics cannot be used because one of the oldest, the electrolytic capacitor, is named instead by its cathode construction.

The most common kinds of capacitors are:

• Electrolytic capacitors
  • Tantalum capacitors
  • Niobium capacitors
  • Aluminum capacitors
• Ceramic capacitors
• Paper capacitors
• Film capacitors
• Mica capacitors
• Supercapacitors
• ….

Typical Values

One farad of capacitance is a relatively large unit of capacitance, and it is not commonly found in most electronic circuits. A capacitor with a capacitance of one farad can store one coulomb (C) of charge per volt of potential difference between its plates. Submultiples of the farad, such as the microfarad and the picofarad, are more convenient units in practice.

To give you an idea of how large one farad is, consider the following examples:

• A typical small ceramic capacitor used in electronics might have a capacitance of around 0.1 microfarads (µF), which is one ten-millionth of a farad.
• A typical electrolytic capacitor used in power supply circuits might have a capacitance of a few hundred or thousand microfarads (µF), which is still many orders of magnitude smaller than one farad.
• A supercapacitor or ultracapacitor, which is a type of high-capacity capacitor used in some energy storage applications, might have a capacitance of several farads or even tens of farads.

In summary, one farad of capacitance is a relatively large unit of capacitance, and capacitors with capacitances in the farad range are typically only used in specialized applications. Most electronic circuits use capacitors with capacitances in the microfarad or picofarad range.