Capacitors store up charge and then release it. How they do that depends on their size and what they are made of. Capacitors are one of the most common electronic components and are available in a wide variety of types of capacitors. Each type of capacitor offers a set of characteristics that make them suitable for certain applications, environments, and products. Capacitors are typically categorized by their form factor and the dielectric material used in the capacitor. Each type of capacitor presents significant differences in typical and available values for capacitance tolerance, voltage rating, temperature stability, equivalent series resistance, size, and reliability that affect how they behave in the real world. These differences influence capacitor selection, making some capacitors great in some applications and a source of trouble in others.
Film capacitors are one of the more common types of capacitors. Film capacitors include a large family of capacitors with the main difference being the dielectric materials used. Common materials used include polyester (mylar), polystyrene, polypropylene polycarbonate, metalized paper, and Teflon. Film capacitors are available in values from pF (picoFarads) up to 100's of uF (microFarads). High-voltage film capacitors, with voltage ratings exceeding 500 volts, top the capability scale. The advantage of film capacitors, especially the film capacitors that use plastic films, are long life and very stable capacitance values. Film capacitors are available in several package sizes and form factors. The most common form factors for film capacitors are cylindrical, oval, round, and rectangular and most form factors are available with axial and radial style leads.
Ceramic capacitors are some of the most common capacitors used, especially in surface-mount applications. They are made by coating a ceramic disc or plate with a conductor and connecting several together. The ceramic used has a very high dielectric constant, which lets ceramic capacitors have a relatively high capacitance value in a small size. Unlike electrolytic capacitors, ceramic capacitors are not polarized but their capacitance goes through a non-linear shift as their temperature changes. For these reasons, ceramic capacitors are often used as decoupling or bypass capacitors. Ceramic capacitors are available in values ranging from a few pF to several uF and have voltage ratings from a few volts to tens of thousands of volts.