The capacitor is made of absorbent paper dipped in paste electrolyte and wound between two aluminum foils with thin oxide film as the dielectric. Because the oxide film has one-way conductive properties, electrolytic capacitors have polarity. Its characteristics are as follows:

1. large capacity, able to withstand large pulsating currents.

2. large capacity error and high leakage current; common ones are not suitable for high frequency and low temperature applications and should not be used in frequencies above 25kHz.

3. low frequency bypass, signal coupling, power filtering.