Selection Guide for Aluminum Electrolytic Capacitors

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What is an aluminum electrolytic capacitor?

Capacitors are passive electronic devices that store electric charge. Polarized aluminum electrolytic capacitors are typically constructed using two rolled layers of aluminum foil separated by a paper insulator saturated with a wet electrolyte. This capacitor’s dielectric consists of this insulator in conjunction with a thin oxide layer formed on the positive foil anode. Electrolytic capacitors have a relatively high capacitance-voltage (CV) rating per unit volume at a low cost. Applications include power supply energy storage as well as signal bypass, coupling, and decoupling.

FAQs for aluminum electrolytic capacitors

Image showing the variety of aluminum electrolytic capacitors offered by DigiKey
Image showing the variety of aluminum electrolytic capacitors offered by DigiKey2068×1185 261 KB

Introduction to DigiKey’s Product Selection Guide

This page is one of many in DigiKey’s Product Selection Guide (PSG). This particular page is focused on aluminum electrolytic capacitors. It provides a description of the individual parameters used to characterize the part. This information will allow you to better understand and navigate DigiKey’s parametric search engine. Click here for a case study showing how to use the search tools.

How are aluminum electrolytic capacitors categorized?

The DigiKey search tools include the following specification for aluminum electrolytic capacitors.

  • Capacitance: A measurement of the device’s ability to store an electrical charge. It is measured in Farads (F) and uses the metric system for values.

  • Tolerance: Characterizes the extent of permitted variability of overall device value among samples of a given part number, resulting from variations in manufacturing.

  • Voltage - Rated: Typically this represents the maximum voltage rating to which a device will meet its given specifications. Exceeding this voltage rating may damage the device and other system components.

  • ESR (Equivalent Series Resistance): All capacitors have an internal resistance. This is similar to the Thevenin source with an ideal capacitor in series with a small output resistor. This ESR is an important consideration for high current circuits that require a low source impedance such as when the capacitor is used as a power supply energy reservoir. A low ESR implies that the capacitor can deliver high current without a drop in voltage.

  • Lifetime @ Temp: Characterizes a device’s longevity in service at the indicated temperature. Refer to the manufacturer’s documentation for supporting information.

  • Operating Temperature: Recommended operating temperature, typically given in a range or as a maximum. Exceeding these temperatures may affect performance or damage the device and other system components. Many capacitors follow the “rule of 10” where service life is doubled for every 10° C reduction in temperature.

  • Polarization: Indicates whether or not a capacitor is designed to tolerate a reversal of applied voltage during normal operation.

  • Ratings: Minimum performance standards of the device, which are typically set by a third party.

  • Applications: Identifies the type of equipment, environment, or function for which the device is intended for use.

  • Ripple Current @ Low Frequency: The maximum allowable current flow through a device at the indicated test frequency. Temperature qualifications apply, see the datasheet for details.

  • Ripple Current @ High Frequency: The maximum allowable current flow through a device at the indicated test frequency. Temperature qualifications apply, see the datasheet for details.

  • Impedance: Impedance is related to ESR, but accounts for the frequency-dependent response of the capacitor. Impedance is usually specified at a given frequency such as 100 kHz.

  • Lead Spacing: Indicates the center-to-center spacing between adjacent leads.

  • Size / Dimension: The physical dimensions of the main body of the device. Typically listed as diameter x height.

  • Height - Seated (Max): Indicates how far the device will extend above the surface to which it has been attached.

  • Surface Mount Land Size: The length and width the space of the device’s main footprint take up on the board.

  • Mounting Type: Indicates how the device is attached.

  • Package / Case: Indicates the type of protective case used on an electronic component to allow easy handling, installation, and protection. This selection was determined to be the closest industry standard applicable to the supplier’s device packaging. Typically, it is best to check the actual dimensions from the datasheet rather than depend on this terminology when designing your circuit.

Examples of aluminum electrolytic capacitors

Image of the Panasonic EEE-HC1C101XP
Image of the Panasonic EEE-HC1C101XP640×640 52 KB


  • The Nichicon brand LNK2H103MSEJ is chassis mount 100,000 uF 500 VDC aluminum electrolytic capacitor shown with mounting bracket and terminal bolts. Datasheet

Image of the Nichicon LNK2H103MSEJ
Image of the Nichicon LNK2H103MSEJ640×640 38.8 KB


Image of the Cornell Dubilier 228TTA050M
Image of the Cornell Dubilier 228TTA050M640×640 24.7 KB


Schematic symbol

The schematic symbol for the polarized and non-polarized aluminum electrolytic capacitor are shown below.

Polarized

Schematic image of a polarized electrolytic capacitor

Non-Polarized

Non-polarized image 2

Schematic symbols courtesy of Scheme-it.

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Follow up

If you have any general questions on the specifications for selecting aluminum electrolytic capacitors, please reply using the button below. If you have questions on a specific capacitor, please post your questions in the forum’s capacitor category.

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