Capacitors: Types, Working, Applications, Selection Guide & Complete Technical Overview

Introduction

A capacitor is one of the most fundamental passive components in electronic circuits. It stores and releases electrical energy in the form of an electric field. Whether you're designing a simple power supply or a complex signal-processing system, capacitors play a vital role in ensuring stability, performance, and signal integrity.

In this guide, we’ll explore what a capacitor is, how it works, its various types, common applications, selection criteria, and even a real-world example — all explained in simple and technical language.

What is a Capacitor?

A capacitor is an electronic component that temporarily stores electrical energy in an electric field. It consists of two conductive plates (electrodes) separated by a dielectric material. When a voltage is applied across the plates, an electric charge builds up and is stored.

How Do Capacitors Work?

Capacitors work based on the principle of electrostatic charge storage. When a voltage is applied:

• One plate accumulates positive charge

• The other accumulates negative charge

• The dielectric prevents direct current flow while allowing the field to build

The amount of charge a capacitor can store is determined by its capacitance, measured in Farads (F). Most practical capacitors are in microfarads (μF), nanofarads (nF), or picofarads (pF).

Capacitance Formula

• CCC = Capacitance (Farads)

• εεε = Dielectric permittivity

• AAA = Area of the plates

• ddd = Distance between the plates

Types of Capacitors (with Keywords)

1. Ceramic Capacitor

• Made from ceramic materials
• Small, inexpensive, and non-polarized
• Common values: 10pF to 100nF
• Ideal for high-frequency applications

2. Electrolytic Capacitor

• Uses electrolyte as dielectric
• High capacitance (1μF to 10,000μF)
• Polarized; used in power supply filters

3. Tantalum Capacitor

• Smaller than electrolytic
• Stable and reliable
• Sensitive to polarity and overvoltage

4. Film Capacitor

• Uses plastic film as dielectric
• Excellent for AC signal and timing circuits
• Highly stable over time

5. Super Capacitor (Ultracapacitor)

• High capacitance (up to thousands of Farads)
• Stores large amounts of energy
• Used in backup power and energy harvesting

6. Mica Capacitor

• Made using mica dielectric
• High precision, low loss
• Expensive, used in RF circuits

7. Paper Capacitor

• Obsolete now; used paper as dielectric
• Replaced by modern film types

Applications of Capacitors

• Power Supply Filtering: Smooth out AC ripple

• Signal Coupling and Decoupling: Isolate AC and DC components

• Energy Storage: Temporary power source

• Timing Circuits: In RC and LC circuits

• Motor Starters: Phase shifting in AC motors

• Tuning Circuits: In radios and oscillators

• Snubber Circuits: Suppress voltage spikes

Capacitor Selection Guide

Real-World Example: Capacitor in Power Supply Filter

Use Case:

Let’s say you are building a DC power supply from an AC source. After rectification, the DC signal has ripples. You can use an electrolytic capacitor to smooth the output.

Working:

• The capacitor charges when voltage rises
• It discharges when voltage drops
• This reduces the ripple and provides a stable DC output

Components Used:

• 1000μF, 25V electrolytic capacitor
• 1N4007 diodes for bridge rectifier
• 12V transformer

Result:

Capacitor Color Code Chart (For Reference)

Note: Modern capacitors often have numerical codes instead.