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Capacitors, Capacitors, Everywhere!

By Robert Cong

What's the difference between capacitors?

One of the most common passive component questions we hear is "What are the differences between the wide varieties of capacitors?" When your schematic calls for a capacitor, you have many choices: electrolytic, ceramic, silver mica, mylar, monolithic, tantalum, glass or supercapacitors, just to name a few. It can be confusing, especially if you have a specific application that requires extra noise filtering or high voltage handling capabilities. Below are some common types of capacitors and what applications they are most often used in:

Ceramic Capacitors

Made of ceramic material as the dielectric and metal as the electrodes, ceramic capacitors come in a variety of shapes and sizes. They are generally less expensive than other capacitors and carry lower capacitances (couple of µF max.), which makes them used often during low capacitance requirements in noise/harmonics filtering and suppression applications. Multiple ceramic layers may also be arranged and compressed together to form a block, reducing equivalent series inductance and creating a monolithic ceramic capacitor.

Electrolytic Capacitors

High capacitance capabilities (1000s of µF) allow these capacitors to store a great amount of energy for their size. There are a few different types of electrolytics, but they mostly use a very thin layer of oxide as the dielectric and a conducting semi-liquid electrolyte as one of the plate electrodes. These polarized capacitors are often used in coupling, ripple smoothing, DC blocking, bypassing, filtering and timing applications.

Polystyrene Capacitors

Using polystyrene film as the dielectric, these capacitors provide high insulation, low distortion, high frequency ranges and good temperature stability. They usually come in a through-hole package, so surface mount packaging is not available. They are widely used in audio applications such as ham radio for EMI/noise filtering and RF coupling.

Mylar Capacitors

Another type of film capacitor, mylar caps have the great properties of high heat and humidity resistance. Because of this, they are able to be used in harsher environment applications like power converters, lighting, timing and communications. Mylars are generally larger in physical size than other caps, taking up more valuable real estate in the process.

Tantalum Capacitors

These are a type of electrolytic capacitor with three different types in itself: tantalum foil electrolytic, tantalum with porous anode and liquid electrolyte, and tantalum with porous anode and solid electrolyte. The tantalum capacitor is known for its high capacitance density. It is also highly reliable in many applications (so long as it is not reverse biased and is not subject to high voltages or ripple currents), although they are mostly used in decoupling, DC blocking, bypassing, filtering and timing applications.

Silver Mica Capacitors

1000pF Silver Mica Capacitor
1000pF Silver Mica Capacitor

Silver mica capacitors have low tolerance levels providing highly accurate and stable performance. The mica dielectric contains thin sheets of silver foil in between to provide a chemically stable structure that does not react to many environmental substances. Greatly used in tuning circuits and harsh environments, silver mica caps are the ones to use for high performance applications that require the most accuracy and dependability.

Of course, every capacitor can be used in many different applications. It just so happens that certain ones do better in some applications than others. Did we forget to mention your favorite cap? Tell us what your favorite type of capacitor is and what applications you use it for on our community forum.
Robert is a graduate from Cal Poly, San Luis Obispo in Electrical Engineering. His interests include sports, movies, music and playing with cool, new gadgets.