The arrangement of plates and dielectric has many variations depending on the desired ratings of the capacitor. For small values of capacitance (microfarads and less), ceramic disks use metallic coatings, with wire leads bonded to the coating. Larger values can be made by multiple stacks of plates and disks. Larger value capacitors usually use a metal foil or metal film layer deposited on the surface of a dielectric film to make the plates, and a dielectric film of impregnated paper or plastic – these are rolled up to save space. To reduce the series resistance and inductance for long plates, the plates and dielectric are staggered so that connection is made at the common edge of the rolled-up plates, not at the ends of the foil or metalized film strips that comprise the plates. COUNT 5
QSN1 What order of magnitude of capacitance is suitable for capacitors comprised of ceramic disks with metallic coatings? ANS1 microfarads and less QSN2 How are larger value capacitors often constructed? ANS2 multiple stacks of plates and disks QSN3 What do larger value capacitors often use as the dielectric medium? ANS3 impregnated paper or plastic – these are rolled up to save space QSN4 Why are the plates and dielectrics often staggered in larger value capacitors? ANS4 To reduce the series resistance and inductance QSN5 How are the conductive plates often made for larger value capacitors? ANS5 metal film layer deposited on the surface of a dielectric film