Electrolytic capacitors are polar capacitors, and their pins are clearly divided into positive and negative poles. When using, the polarity of the pins cannot be reversed.

Common electrolytic capacitors can be divided into aluminum electrolytic capacitors and tantalum electrolytic capacitors according to different electrode materials.

1 Aluminum electrolytic capacitor

Aluminum electrolytic capacitors are liquid electrolytic capacitors. According to the state of the dielectric material, they can be divided into ordinary aluminum electrolytic capacitors (liquid aluminum electrolytic capacitors) and solid aluminum electrolytic capacitors (solid capacitors). They are currently the most widely used capacitors.

Aluminum electrolytic capacitors have large capacitance, low insulation resistance, large leakage current, and poor frequency characteristics. The capacitance and loss will change with the surrounding environment and time, especially when the temperature is too low or too high, and it is not used for a long time. It will fail, and it is mostly used in low frequency and low voltage circuits.

The pins of ordinary aluminum electrolytic capacitors are divided into polarities, and the identification information is marked on the surface.

The parameter information of the solid aluminum electrolytic capacitor is marked on the top, and the pin on the side with the black mark is the negative pin.

The specifications of aluminum electrolytic capacitors are various, and the shape is also different due to the different manufacturing processes. Commonly used are welding pin-shaped aluminum electrolytic capacitors, bolt-shaped aluminum electrolytic capacitors, and axial aluminum electrolytic capacitors.

2 Tantalum electrolytic capacitors

Tantalum electrolytic capacitors are capacitors made of metal tantalum as the positive electrode material.

Tantalum electrolytic capacitors mainly include solid tantalum electrolytic capacitors and liquid tantalum electrolytic capacitors.

According to the different installation forms, solid tantalum electrolytic capacitors can be divided into discrete solid tantalum electrolytic capacitors and chip solid tantalum electrolytic capacitors.

The temperature characteristics, frequency characteristics and reliability of tantalum electrolytic capacitors are better than aluminum electrolytic capacitors, especially the leakage current is extremely small, the charge storage capacity is good, the life is long, and the error is small, but the price is higher, and it is usually used in high-precision electronic circuits. . About the leakage current of the capacitor: When a DC voltage is applied to the capacitor, since the medium of the capacitor is not an absolute insulator, the capacitor will have a leakage current. If the leakage current is too large, the capacitor will be burned out due to heat. Generally, the leakage current of electrolytic capacitors is relatively large, so the leakage current is often used to represent the insulation performance of electrolytic capacitors.

About the leakage resistance of capacitors: Since the medium between the two poles of the capacitor is not an absolute insulator, the resistance is not infinite, but a finite value, generally very accurate, such as 534kΩ, 652kΩ. The resistance between the two poles of the capacitor is called insulation resistance, also known as leakage resistance. Its size is the ratio of the DC voltage at the rated operating voltage to the leakage current through the capacitor. The smaller the leakage resistance, the more serious the leakage. Capacitor leakage can cause energy loss that affects not only service life but also circuit performance. Therefore, the larger the leakage resistance of the capacitor, the better.