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 A tantalum capacitor is a type of electrolytic capacitor, a component of electronic circuits. It typically consists of a pellet of tantalummetal as anode, covered by an insulating oxide layer that forms the dielectric, surrounded by conductive material as a cathode. Tantalum capacitors are the main use of the element tantalum.

The tantalum capacitor distinguishes itself from other capacitors in having high capacitance per volume and weight. Tantalum capacitors have lower equivalent series resistance (ESR), lower leakage, and higher operating temperature than other electrolytic capacitors, although other types of capacitors are even better in these regards.

Tantalum capacitors are considerably more expensive than any other commonly used type of capacitor, so they are used only in applications where the small size or better performance are important.

Tantalum electrolytic capacitors exploit the tendency of tantalum to form a non-conductive protective oxide surface layer. A tantalum capacitor consists of tantalum powder pressed into a pellet shape as one "plate" of the capacitor, with the oxide as a dielectric, and an electrolytic solution or conductive solid as the other "plate". The dielectric layer thus can be very thin (thinner than the similar layer in, for instance, an aluminum electrolytic capacitor).

The capacitor typically consists of a sintered tantalum metallic sponge acting as the anode, a manganese dioxide cathode, and a dielectric layer of tantalum pentoxidecreated on the tantalum sponge surface by anodizing.

Because of its thin dielectric, a tantalum capacitor can have high capacitance in a small volume (high volumetric efficiency). The size and weight advantages make tantalum capacitors attractive for portable telephones, compact personal computers, and automotive electronics.

The steady-state and dynamic reliability of a tantalum capacitor are influenced by several factors under the control of the circuit design engineer. These factors are voltage derating, ripple current and voltage conditions, maximum operating temperature, and circuit impedance. Tantalum capacitors have very low electrical leakage (high leakage resistance), so will retain a charge for a long time. They tolerate hot operating environments up to 125 °C, unlike most aluminum electrolytic capacitors.

Tantalum capacitors have lower equivalent series resistance (ESR) than aluminum electrolytic capacitors of the same capacitance, which is a significant advantage in many designs. However, care must be taken when designing a circuit using tantalum capacitors, to limit charge and discharge currents (particularly those of a repetitive nature) to a level that does not overstress other circuit components.

Tantalum capacitors are relatively expensive, particularly in the mil-spec grades.

Tantalum capacitors are extremely reliable. However, their failure mode tends to be a short-circuit, due to the extremely thin dielectric; designs using these capacitors need to take into account the consequences of this possible failure mode. There is also a possibility of catastrophic thermal runaway failure (see below).

Because most tantalum capacitors being made as of 2012 are solid (no liquid electrolyte), there is no known wear-out mechanism. Solid-bodied tantalum electrolytic capacitors are less prone to "drying out" than aluminum capacitors, which tend to decrease in capacitance (and increase in ESR) particularly when used in hot environments. When operated within their design limits, tantalum capacitors can maintain their designed capacitance under such conditions for decades.
 the low leakage and high capacity of tantalum capacitors favor their use in sample and hold circuits to achieve long hold duration, and some long duration timing circuits where precise timing is not critical. They are also often used for power supply rail decoupling in parallel with film or ceramic capacitors which provide low ESR and low reactance at high frequency. Tantalum capacitors can replace aluminum electrolytic capacitors in situations where the external environment or dense component packing results in a sustained hot internal environment and where high reliability is important. Equipment such as medical electronics and space equipment that require high quality and reliability makes use of tantalum capacitors.

An especially common application for low-voltage tantalum capacitors is power supply filtering on computer motherboards and in peripherals, due to their small size and long-term reliability.[2][3]

When applying tantalum capacitors, the possibility of thermal runaway (see above) or spontaneous short-circuiting must be considered. In many cases, a failed capacitor will only make the circuit stop functioning normally. However, if sufficient power is available, catastrophic thermal runaway may cause a fire or small explosion. A design can prevent this by using external current limiting (e.g. thermal fuse, circuit breaker).

the low leakage and high capacity of tantalum capacitors favor their use in sample and hold circuits to achieve long hold duration, and some long duration timing circuits where precise timing is not critical. They are also often used for power supply rail decoupling in parallel with film or ceramic capacitors which provide low ESR and low reactance at high frequency. Tantalum capacitors can replace aluminum electrolytic capacitors in situations where the external environment or dense component packing results in a sustained hot internal environment and where high reliability is important. Equipment such as medical electronics and space equipment that require high quality and reliability makes use of tantalum capacitors.

An especially common application for low-voltage tantalum capacitors is power supply filtering on computer motherboards and in peripherals, due to their small size and long-term reliability.[2][3]

When applying tantalum capacitors, the possibility of thermal runaway (see above) or spontaneous short-circuiting must be considered. In many cases, a failed capacitor will only make the circuit stop functioning normally. However, if sufficient power is available, catastrophic thermal runaway may cause a fire or small explosion. A design can prevent this by using external current limiting (e.g. thermal fuse, circuit breaker).