Capacitor Technology

What Is a Capacitor?

A capacitor is a passive electronic component that stores an electric charge and can be either polarized or non-polarized. The construction of a capacitor includes two conductors (plates) separated by an electrical insulator called a dielectric. The plates accumulate an electric charge when connected to a power source. One plate accumulates a positive charge, and the other plate accumulates a negative charge. Capacitors are offered in a variety of materials, shapes, and sizes, which offer different performance characteristics.

Capacitor Applications

Capacitors are used in a multitude of applications in electronic circuits to enable stable and reliable operation of the circuits. The most common uses of capacitors in circuits are for filtering, coupling, and decoupling:

Filtering: The main function of a capacitor in a filtering application is to filter out unwanted noise and ripple voltage in a power-supply circuit, resulting in a more stable and smoother output voltage. The capacitor stores energy that is fed into a circuit on demand when there are sudden increases in required power.
Coupling: In a coupling application, a capacitor is used to link an AC signal between two elements in a circuit. The DC signal is blocked by the capacitor, so it is prevented from entering the second element.
Decoupling: Digital circuits can sometimes be contaminated with noise from other devices in the circuit. The result is transient loads that cause fluctuating current draw, which generates unwanted noise at the power source. Capacitors are used to protect the power source from the noise generated within the circuit as well as noise generated by other devices connected to the same power source.

Capacitor Operating Considerations

Capacitors come in a multitude of formats, shapes, and sizes, with a variety of performance characteristics. Choosing the right capacitor for an application is essential to the stable operation of the circuit.
In terms of voltage, it is important to ensure that the maximum circuit voltage will not exceed the capacitor’s rated voltage. If the circuit voltage exceeds the rated voltage of the capacitor, the capacitor may short-circuit internally.
Also, the designer must calculate the required capacitance value for a circuit, taking into consideration both the maximum charge to be stored and the applied voltage. There are mathematical equations that circuit designers use to calculate the capacitance required for a circuit, and it is important to ensure that the designer also considers the capacitance tolerance of the capacitor selected.
Finally, while many capacitors are non-polarized, and so do not have positive/negative terminal designations, electrolytic capacitors are polarized and must be placed in the circuit with correct polarity orientation.

Tecate Product Offerings

At Tecate Group, we offer several varieties of capacitors. They are grouped by the material from which they are constructed.

Ceramic capacitors: Ceramic capacitors are made of two or more alternating layers of ceramic dielectric material with a metal electrode between each layer. There are various compositions of ceramic materials used to produce these capacitors, which ultimately defines the electrical specifications of the capacitor. Ceramic capacitors are the most widely used capacitor on the market, are low in cost, and come in a variety of shapes and sizes. Ceramic capacitors are non-polarized.
Film capacitors: Film capacitors are made of two pieces of a very thin plastic film that serves as the dielectric insulating material. The film pieces have one side covered with a metallic material for the electrode, which is then wound into a cylindrical shape and encapsulated. Very reliable, film capacitors have a long shelf life and long service life. Their only drawback is their larger size compared to other capacitors. Film capacitors are non-polarized.
Electrolytic capacitors: Electrolytic capacitors use an electrolyte with a high concentration of ions that enables a much larger capacitance value than other types of capacitors. The electrolyte can be a liquid, a gel, or a solid. All electrolytic capacitors are polarized, so they have a negative and a positive terminal. There are three types of electrolytic capacitors offered by Tecate Group:
- Aluminum electrolytic: Aluminum electrolytic capacitors include an aluminum foil anode with an etched surface that forms a very thin surface of aluminum oxide, which acts as the dielectric. A second layer of aluminum foil is in contact with the electrolyte and serves as the cathode, which is the negative side of the capacitor. The anode and cathode are physically separated by a spacer, usually paper.
- Tantalum electrolytic: A tantalum electrolytic capacitor is the same as an aluminum electrolytic capacitor, except that it uses tantalum instead of aluminum. Tantalum enables a very high capacitance per volume and lower weight as compared to other capacitor types but is also considerably higher in cost.
- Conductive polymer: Conductive polymer capacitors use solid conductive polymers as the electrolyte instead of the liquid or gel that is normally used in electrolytic capacitors. The solid electrolyte cannot dry out, as can happen with wet electrolyte capacitors. The superior qualities of conductive polymer capacitors include longer life, higher temperature range, and better stability.

Feature	Ceramic	Film	Electrolytic
Feature	Ceramic	Film	Aluminum	Tantalum	Polymer
Voltage	4V to 6,000V	16V to 3,000V	4V to 450V	2.5V to 50V	2.5V to 100V
Capacitance	0.1pF to 100uF	0.001uF to 25uF	0.1uF to 68,000uF	0.1uF to 680uF	1.7uF to 3,500uF
Polarized	No	No	Yes	Yes	Yes
Life	Long	Long	Limited	Long	Long
Cost	Low	Low	Low	High	High
Advantages	Small size; low cost	Quality/accuracy	Large capacitance; high voltage	Small size; reliability	Long life; low ESR
Disadvantages	Poor temperature characteristics	Large size	High leakage current; high ESR; limited life	Cost	Cost