Capacitors are designed to store electrical charge. When connected to a power source, one plate of the capacitor accumulates electrons, while the other plate develops an equal but opposite charge.

Fundamentals of Capacitors

A capacitor is a device that passively stores electrical energy in an electric field. It consists of two conductive plates separated by a dielectric, an insulating material. When voltage is applied across the plates, an electric field forms within the dielectric, causing a charge to build up.

The primary function of capacitors is to store charge. When a capacitor is connected to a power source, electrons accumulate on one plate, while an equal but opposite charge builds up on the other plate. The amount of charge a capacitor can hold is influenced by the surface area of the plates, the distance between them, and the type of dielectric material used. This capacity is measured in farads (F).

Types of Capacitors You should know

A Guide to Capacitor Symbols

Image	Capacitor symbol	Type of Capacitor
	Figure 2: Bipolar Capacitor Symbol	Bipolar Capacitor
	Figure 3: Butterfly Capacitor Symbol	Butterfly Capacitor
	Figure 4: Differential Capacitor Symbol	Differential Capacitor
	Figure 5: Feed through Capacitor Symbol	Feed through Capacitor
	Figure 6: Generic Capacitor Symbol	Generic Capacitor
	Figure 7: Polarized Electrolytic Capacitor Symbol	Polarized Electrolytic Capacitor
	Figure 8: Split Stator Capacitor Symbol	Split Stator Capacitor
	Figure 9: Trimmer Capacitor Symbol	Trimmer Capacitor
	Figure 10: Variable Capacitor Symbol	Variable Capacitor

Video Related to Capacitor Symbols

Some Common Capacitor Symbols You Should Know

Image	Capacitor symbol	Type	Description
	Figure 11: Disc ceramic Capacitor Symbol	Disc ceramic Capacitor	Disc ceramic capacitors are widely used in electronic circuits. On both sides of the ceramic discs are metal electrodes. Disc ceramic capacitors have a stable and reliable dielectric, which makes them adaptable.
	Figure 12: Multilayer Ceramic Capacitor Symbol	Multilayer Ceramic Capacitor (MLCC)	Metal electrodes are placed on opposite sides of ceramic layers in multilayer ceramic capacitors, or MLCCs. Ceramic layers are stacked as dielectrics to get the desired capacitance.
	Figure 13: Metalized Film Capacitor Symbol	Metalized Film Capacitor	Metalized film capacitors use a thin plastic film as the electrode and one or both sides coated in metal as the dielectric. Aluminum or zinc is deposited onto the plastic sheet through metalization.
	Figure 14: Mica Capacitor Symbol	Mica Capacitor	Thin mica sheets with metal electrodes on either side are known as mica capacitors. They are low-loss and stable for high-frequency applications. Mica capacitors are needed in RF, filter, and high-precision timing circuits.
	Figure 15: Aluminum Electrolytic Capacitor Symbol	Aluminum Electrolytic Capacitor	Aluminum oxide is used as a dielectric in aluminum electrolytic capacitors. They are widely used in electrical circuits due to their inexpensive cost, high voltage, and high capacitance.
	Figure 16: Tantalum Electrolytic capacitor symbol	Tantalum Electrolytic capacitor	Tantalum electrodes are used in tantalum electrolytic capacitors. These capacitors are widely used in electrical circuits due to their high capacitance density, stability, and dependability.
	Figure 17: Niobium Electrolytic Capacitor Symbol	Niobium Electrolytic Capacitor	Niobium oxide dielectrics are found in niobium electrolytic capacitors. They need to be connected correctly since they are polarized similarly to tantalum electrolytic capacitors.
	Figure 18: Aluminum Polymer Capacitor Symbol	Aluminum Polymer Capacitor	Conductive polymers are used in aluminum polymer capacitors in place of liquid or gel electrolytes. They are more dependable, stable, and age- and temperature-resistant.
	Figure 19: Variable Vacuum Capacitor Symbol	Variable Vacuum Capacitor	Two conducting plates that are vacuum-separated make vacuum capacitors. These capacitors are appropriate for high-power RF circuits in transmitters, transceivers, and amplifiers because of their high voltage rating and capacitance density.
	Figure 20: Variable Air Gap Capacitor Symbol	Variable Air Gap Capacitor	A little air gap divides the two conducting plates of an air gap capacitor. They are used in high-frequency, high-voltage applications where other capacitors would not function.
	Figure 21: Ceramic Trimmer Capacitor Symbol	Ceramic Trimmer Capacitor	Ceramic trimmer capacitors adjust the capacitance in a circuit. They have two conductive plates with one on a moveable arm to change the capacitance value and the other two separated by a ceramic dielectric material.
	Figure 22: Film Trimmer Capacitor Symbol	Film Trimmer Capacitor	Another variable capacitor used to adjust circuit capacitance is the film trimmer capacitor. They have two conductive plates with one on a moveable arm to change the capacitance value and the other two separated by a thin layer of dielectric substance.
	Figure 23: Supercapacitor Symbol	Supercapacitor	Supercapacitors can display both positive and negative polarity indicators. Supercapacitors are used in electronics, electric vehicles, and renewable energy systems to provide high power and fast charge/discharge cycles.
	Figure 24: Motor Run and Start Capacitor Symbol	Motor Run and Start Capacitor	The choice and installation of the motor run and start capacitor determine performance and dependability. Take into account the capacitance, voltage, and other features when selecting a capacitor for a motor application.

Capacitor Symbol Naming Rules

Different Standards for Capacitor Symbols

Basic Concepts of Multimeter

How to use a multimeter to measure capacitors

Creating a Capacitor Symbol in Altium Designer

Step-by-Step Guide

Open Altium Designer

Launch the software and open a new or existing project.

Create a Schematic Library

Go to: File > New > Library > Schematic Library.

This will open a new schematic library tab.

Create a New Component

In the schematic library tab, right-click in the Components list and select New Component.

Name your component, such as "Capacitor".

Draw the Capacitor Symbol

Select Place > Line from the top menu to draw the capacitor plates.

For a non-polarized capacitor, draw two parallel lines. For a polarized capacitor, vary the line lengths.

Add Pins

Select Place > Pin.

Click at the ends of each line to place pins. These represent the electrical connections.

Configure Pins

Double-click each pin to open the pin properties dialog.

Set properties such as pin name and electrical type (e.g., Passive, Electrical).

Define Component Properties

With the symbol selected, fill out the Properties panel with details like designator (e.g., C?), description, etc.

Save the Schematic Library

Click File > Save As to save your library with an appropriate name in a designated location.

Compile and Add Library to the Project

Right-click the library in the Projects panel and select Compile Library.

Add the library to your project: Project > Add Existing to Project.

Place the Capacitor in a Schematic

Open a schematic sheet, then go to Place > Component, and select the capacitor from your library.

Click to place the capacitor in the schematic.

Capacitor Symbol FAQs

What is a capacitor symbol?

A capacitor is depicted in electronic schematics by a symbol that typically consists of two parallel lines. Polarized capacitors may have one straight line and one curved line to indicate polarity.

How do I create a capacitor symbol in Altium Designer?

To create a capacitor symbol in Altium Designer, open a new schematic library, create a new component, draw the capacitor plates using the 'Place Line' tool, add pins, configure properties, save the library, compile it, and then add it to your project for use in schematics.

What is the difference between symbols for polarized and non-polarized capacitors?

Non-polarized capacitors are represented by two parallel lines. Polarized capacitors, such as electrolytic capacitors, are shown with a single curved line for the negative terminal and a single straight line for the positive terminal.

Can I modify an existing capacitor symbol in Altium Designer?

Yes, you can modify an existing symbol by opening the schematic library where it is stored, selecting the symbol, making the necessary changes, and saving the modifications. Recompile the library after making any changes.

Why do capacitor symbols in schematics sometimes have different shapes?

Different shapes or variations in capacitor symbols are often used to represent different types of capacitors (such as ceramic, electrolytic, and tantalum), each with unique characteristics and applications in circuits. These variations help quickly distinguish between different types.

How can I ensure my capacitor symbol meets industry standards?

When creating your symbols, refer to industry standard documents such as IEEE or IEC guidelines. Adhering to these standards ensures readability and compatibility across various platforms and teams.

What should I do if my capacitor symbol is not visible after inserting it into a diagram?

Ensure that the library has been correctly added to the project and compiled. In your schematic, check that the layer and visibility settings are not hiding the symbol.

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