The Steady-state Tantalum Capacitor

The tantalum capacitor is a highly reliable type of solid capacitor or electrolytic capacitor. Surface mount tantalum capacitors are increasingly being used in circuit designs because of their volumetric efficiency, basic reliability and process compatibility. The 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 possess very low electrical leakage (high leakage resistance), and will retain a charge for a long duration. They are tolerant of hot operating environments up to 125 °C, unlike standard aluminum electrolytic capacitors.

Tantalum capacitors are not particularly tolerant of heavy charge and discharge currents, particularly those of a repetitive nature, and their effective series resistance (ESR) can be high when compared to ceramics or aluminum electrolytics. Most tantalum capacitors are polarized devices; correct polarity must be observed, otherwise the capacitor will depolarize and the dielectric oxide layer will break down, reducing the resistance of the device and causing it to fail. Tantalum capacitors are relatively expensive, particularly the military grades.

The low leakage and high capacity of tantalum capacitors favors 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 orceramic capacitors with low ESR and 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 make use of tantalum capacitors.