Identifying Capacitor Polarization

Polarized capacitors will always have some sort of designator on them identifying polarity. This is important, because hooking one up backwards can be dangerous.

Aluminum caps can be marked in a number of different ways. Radial, through-hole cans will commonly have a line down the negative side of the body, with the negative lead being shorter as well. Radial, surface mount cans will have a colored portion on the top indicating the negative pad. Axial cans will have a line on one side with arrows pointing to the negative lead, or an indented band that designates the positive lead.

Surface mount tantalum chips will have a line and/or a notch on the positive end. Axial will have a notch on the positive side. Radial has either an arrow or positive indicator above the positive lead.

Below are some images of the examples above with full descriptions of what each one is. If you’re working with these products and are unsure or having a hard time deciphering, you can always refer to the datasheet or contact someone for assistance.

Figure 1: Line and short lead indicate negative lead

Figure 2: Colored block on top indicates negative lead

Figure 3: Line with arrows are pointing at negative lead

Figure 4: Indented band and + signs indicate positive lead

Figure 5: Chamfered edge and line indicate positive lead

Figure 6: Chamfered edge indicates positive lead

Figure 7: Line and + symbol are difficult to see here, but if you can see them on the image they indicate the positive lead.

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Ashley Awalt is a Technical Content Developer that has been with Digi-Key Electronics since 2011. She earned her Associate of Applied Science degree in Electronics Technology & Automated Systems from Northland Community & Technical College through the Digi-Key scholarship program. Her current role is to assist in creating unique technical projects, documenting the process and ultimately participating in the production of video media coverage for the projects. In her spare time, Ashley likes to – oh, wait, is there such a thing as spare time when you’re a mom?

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