Film Capacitors

Film capacitors are one of the most common forms of capacitors used within circuits - especially by electronics hobbyists. They are non-polarized capacitors that are incredibly versatile and cost-efficient, making them a crucial component when constructing circuits.

You can browse our full range from a variety of metalized and non-metalized film capacitor manufacturers, so you can get access to top-quality components from leading brands. Whether you're looking for Vishay, Panasonic, KEMET, Genteq capacitors, or otherwise, we've got the components that will meet practically any specifications you may have.

What is a film capacitor?

Film capacitors are common passive electrical components, made up of two pieces of plastic film covered with metallic electrodes. They are wound into a cylindrical shape, have terminals attached, and are encapsulated in a protective coating.

All film capacitors are non-polarized, meaning the two terminals are interchangeable within the circuit. You can also get metalized film capacitors that differ in terms of the dielectric:

• Non-metalized film capacitors, or metal foil capacitors, are constructed with the two plastic films as the dielectric. These are layers with some form of thin metal foil as the electrode, which allows for a simple electrical connection and capability to handle high surges.
• Metalized film capacitors are made using two films that have vacuum-deposited aluminum metallization applied to them, with the plastic films still acting as the dielectric. This construction can have additional benefits, such as a 'self-healing' property that can avoid the component being destroyed in a short circuit situation.

Types of film capacitor materials

You can find a wide array of polymer film capacitors available on the market, with the different types of insulation material adding useful properties. These properties, specifically their low distortion factor and great frequency characteristics, can make certain film capacitors better for particular applications.

Plastic film capacitors, rather than their metalized counterparts, can be well suited for handling large current surges, which can be useful in certain circuit configurations.

Polyester film capacitor

This is a capacitor that makes use of a dielectric formed from polyethylene terephthalate (PET), leading to the alternative name of PET film capacitor. Using polyester capacitors gives you a low-cost circuit capacitor solution that offers long-term stability. They can be popular choices for simple filter circuits.

In addition to the high insulation strength and operating temperatures of up to 125°C, with a tolerance of 5-10%, polyester film capacitors also display great resistance to humidity. These attributes show how this type of capacitor could be well suited to a variety of circuits.

Polypropylene capacitor

Polypropylene film capacitors are constructed from a polypropylene (PP) polymer that acts as dielectric. One of the key characteristics of these capacitors is the low electrical losses found when inserted into a circuit. This can be crucial when a consistent power output is required.

They also display a behavior that is close to linear over a very wide frequency range. This makes them suitable for stability Class 1 applications in resonant circuits, with the only other viable option being ceramic capacitors.

Polystyrene capacitor

Using polystyrene as the main plastic dielectric, polystyrene capacitors are fantastic for applications where space is limited. This is because they are physically smaller than many other types of capacitors.

Polystyrene film capacitors have good levels of temperature stability and insulation, while also having low leakage and dielectric absorption. These characteristics can make them a suitable alternative to ceramic capacitors.

Polyphenylene sulfide film capacitor

These capacitors have an insulator/dielectric made of polyphenylene sulfide (PPS), which can withstand high temperatures and current surges. Being lightweight and compact capacitors as well, they can be valuable components for surface mount devices (SMD) and are suitable for reflow soldering.

What are film capacitors used for?

Film capacitors are used within circuits for a wide variety of applications, varying on whether they're metalized or not:

• Polyester film capacitors are frequently used for coupling, decoupling, and bypassing. They can be used in both AC and DC applications.
• Polypropylene capacitors are used for switching power supplies, high voltage circuit applications, and lighting ballast systems.
• Metalized film capacitors (both PET and PP) are widely used in power electronic circuits, such as DC link circuits and pulse circuits, with low power variants being useful in filtering applications.
• The most common form of motor run capacitors is metalized polypropylene capacitors. Motor run capacitors are designed to assist single-phase AC electric motors by energizing the second-phase winding. Because they're run continuously within the circuit, low-loss polymer capacitors like polypropylene are preferred.

No matter the type of circuit you're designing, you'll likely find a form of film capacitor that will suit your intended purpose.

Find your film capacitors with RS

Our extensive range of film capacitors covers all the different materials and variations you could potentially need for your circuit designs. We've been distributing top-quality electrical components and electromechanical products across North America for over 90 years, providing our customers with capacitors, circuit components, and more.

If you're looking to bulk order a range of components, you can complete our part quote form for one of our team to discuss with you. For any other queries you may have, you can contact one of our regional sales offices for support or head to our expert advice hub.