The engineer’s guide to tantalum electrolytic capacitors

What is a tantalum electrolytic capacitor?

Tantalum electrolytic capacitors are often used as an upgrade technology to replace aluminum electrolytic capacitors. It’s important to contrast the two technologies.

Tantalum capacitors have thin dielectric layers that result in higher capacitance per unit of volume when compared to aluminum electrolytic capacitors. Their compactness makes them important candidates for weight-sensitive applications like aerospace and portable applications. Tantalum capacitors (like aluminum electrolytic capacitors) thrive in the military temperature range  of -55° C to 125° C. This opens commercial applications (0 to 70° C), industrial uses (-40° C to 85° C) and automotive products (-40° C to 105° C).

Tantalum capacitors also provide excellent reliability. Their capacitance rises with temperature, making them a good fit for power supply applications. An increase in the load produces more heat, which increases their capacitance, which is precisely the correct way to counter increased load.

Tantalum electrolytic capacitors are polarized. Polarized capacitors have an asymmetrical construction in which the anode terminal must always be more positive than the cathode terminal.

In contrast, aluminum electrolytic capacitors do not offer the same capacitance per unit of volume advantage provided by tantalum capacitors. However, their price and availability are strong points. The lifespan of aluminum electrolytic capacitors depends on their environment. Ambient temperature, operating voltage and ripple current are obvious concerns, but vibration, humidity and even atmospheric pressure are impactful. Treated well, aluminum electrolytic capacitors can enjoy a long life.

The niobium electrolytic capacitor is another alternative to tantalum electrolytic capacitors. Niobium electrolytic capacitors offer additional safety features such as higher flame retardation.

Applications of tantalum electrolytic capacitors

Tantalum electrolytic capacitors are used in many applications. They are one of the most prevalent types of capacitors due to their much higher charge capacity when compared to film or ceramic capacitors, thanks to the high permittivity of the tantalum dielectric constant. Tantalum electrolytic capacitors have also less leakage and higher frequency response than aluminum electrolytic capacitors. Therefore, tantalum electrolytic capacitors are preferred in various electronic applications where small size and higher-frequency operation is required.

Tantalum electrolytic capacitors are used widely in computers, television, radios, cell phones and test equipment. About 80% of tantalum electrolytic capacitors are manufactured in surface mount device (SMD) form. Tantalum electrolytic capacitors are an attractive option for meeting energy efficiency requirements because of their low equivalent series resistance (ESR) and low leakage current.

Alternatives to tantalum electrolytic capacitors

For filtering, coupling, decoupling and bypassing, circuit designers will typically choose between aluminum electrolytic, tantalum electrolytic, niobium electrolytic and multilayer ceramic chip (MLCC) capacitors. The following table provides an overview of these choices.