Electrolytic capacitor is a kind of capacitor. The metal foil is the positive electrode (aluminum or tantalum), and the metal oxide film (aluminum oxide or tantalum pentoxide) close to the positive electrode is the dielectric. The cathode is made of conductive materials and electrolyte (the electrolyte can be liquid or Solid) and other materials are composed together. Because the electrolyte is the main part of the cathode, the electrolytic capacitor is named after it. At the same time, the positive and negative electrolytic capacitors cannot be connected wrongly. Aluminum electrolytic capacitors can be divided into four categories: lead-type aluminum electrolytic capacitors; horn-type aluminum electrolytic capacitors; bolt-type aluminum electrolytic capacitors; solid aluminum electrolytic capacitors. Polarized electrolytic capacitors usually play a role in power supply circuits or intermediate frequency and low frequency circuits for power supply filtering, decoupling, signal coupling, time constant setting, and DC blocking. Generally cannot be used in AC power circuits. When used as filter capacitors in DC power circuits, its anode (positive) should be connected to the positive terminal of the power supply voltage, and the cathode (negative) should be connected to the negative terminal of the power supply voltage, not reversed. , Otherwise it will damage the capacitor.

·The capacitance per unit volume is very large, tens to hundreds of times larger than other types of capacitors.

·The rated capacity can be very large, which can easily be tens of thousands of μf or even a few f (but not comparable to the electric double layer capacitance).