01-04-2014, 02:55 PM
Electrolytic capacitors
[attachment=60743]
INTRODUCTION
Electrolytic capacitors have a metallic anode covered with an oxidized layer used as dielectric. The second electrode is a non-solid (wet) or solid electrolyte. Electrolytic capacitors are polarized. Three families are available, categorized according to their dielectric.
Aluminum electrolytic capacitors with aluminum oxide as dielectric
Tantalum electrolytic capacitors with tantalum pentoxide as dielectric
Niobium electrolytic capacitors with niobium pentoxide as dielectric.
The anode is highly roughened to increase the surface area. This and the relatively high permittivity of the oxide layer gives these capacitors very high capacitance per unit volume compared with film- or ceramic capacitors.
The permittivity of tantalum pentoxide is approximately three times higher than aluminium dioxide, producing significantly smaller components. However, permittivity determines only the dimensions. Electrical parameters, especially conductivity, are established by the electrolyte's material and composition. Three general types of electrolytes are used:
non solid (wet, liquid)—conductivity approximately 10 mS/cm and are the lowest cost
solid manganese oxide—conductivity approximately 100 mS/cm offer high quality and stability
solid conductive polymer (Polypyrrole)—conductivity approximately 10,000 mS/cm,[21] offer ESR values as low as <10 mΩ
Internal losses of electrolytic capacitors, prevailing used for decoupling and buffering applications, are determined by the kind of electrolyte.
[attachment=60743]
INTRODUCTION
Electrolytic capacitors have a metallic anode covered with an oxidized layer used as dielectric. The second electrode is a non-solid (wet) or solid electrolyte. Electrolytic capacitors are polarized. Three families are available, categorized according to their dielectric.
Aluminum electrolytic capacitors with aluminum oxide as dielectric
Tantalum electrolytic capacitors with tantalum pentoxide as dielectric
Niobium electrolytic capacitors with niobium pentoxide as dielectric.
The anode is highly roughened to increase the surface area. This and the relatively high permittivity of the oxide layer gives these capacitors very high capacitance per unit volume compared with film- or ceramic capacitors.
The permittivity of tantalum pentoxide is approximately three times higher than aluminium dioxide, producing significantly smaller components. However, permittivity determines only the dimensions. Electrical parameters, especially conductivity, are established by the electrolyte's material and composition. Three general types of electrolytes are used:
non solid (wet, liquid)—conductivity approximately 10 mS/cm and are the lowest cost
solid manganese oxide—conductivity approximately 100 mS/cm offer high quality and stability
solid conductive polymer (Polypyrrole)—conductivity approximately 10,000 mS/cm,[21] offer ESR values as low as <10 mΩ
Internal losses of electrolytic capacitors, prevailing used for decoupling and buffering applications, are determined by the kind of electrolyte.