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ManualsBrandsWÜRTH ELEKTRONIK ManualsElectronics TextbooksAbc of Capacitors 978-3-8992-9294-7

1 Basic Principles

1.8 Capacitor

Dependent upon the field pattern, the area A through which field line pass perpendicu-

larly is of a different size.

The strength of the electric field is described by the displacement flux density D (also

known in the literature as electric field density). The displacement flux density D is

the displacement flux per unit area through which field lines pass perpendicularly. The

displacement flux density is determined by the quotient of the quantity of charge on

the plates, which in this case corresponds to the displacement flux ψ and the effective

area A through which field lines pass:

[D] =

(1.8)

The displacement flux density is a vectorial quantity and is directly proportional to the

existing field strength E.

If there is a vacuum between the plates, the flux density can be determined by

multiplying the electric field constant and the electric field strength:

D = ε

* E (vacuum as dielectric) (1.9)

If another insulating material or another dielectric is introduced, the following equation

applies for calculating the displacement flux density:

D = ε

* ε

* E (arbitrary dielectric) (1.10)

In case of any other dielectric, the displacement flux density is determined by multi-

plying the electric field constant ε

with the relative permittivity of the respective

dielectric ε

and the electric field strength E.

1.8 Capacitor

A capacitor describes every arrangement for storing stationary electric charges. The

structure of a capacitor always consists of two conducting surfaces, the so-called

electrodes (often termed as sheets). They are always separated from one another

Displacement flux

density D

Capacitor

Summary of content (4 pages)

PAGE 1
Basic Principles 1.8 Capacitor Dependent upon the field pattern, the area A through which field line pass perpendicularly is of a different size. The strength of the electric field is described by the displacement flux density D (also known in the literature as electric field density). The displacement flux density D is the displacement flux per unit area through which field lines pass perpendicularly.
PAGE 2
1 Basic Principles 1.8 Capacitor by an insulating material, the dielectric. The principle construction of a capacitor is illustrated as follows: Fig. 1.6: Principle construction of a capacitor Plate capacitor The most commonly used arrangement as a technology is the plate capacitor. The principle structure of a plate capacitor consists of two metal plates or foils and a dielectric in the space between them. A plate capacitor and its essential parameters are presented in the following Figure 1.7: Fig. 1.
PAGE 3
1 Basic Principles 1.8 Capacitor The area A is determined from the length L and width W of the electrodes: A = L * W (1.12) The capacitance C is calculated from the field constant ε0, the relative permittivity εr of the dielectric used, the effective area A (the overlapping area of the electrodes) and the thickness d of the dielectric or the separation produced between the electrodes.
PAGE 4
1 Basic Principles 1.8 Capacitor Capacitor types There are various types and constructions of capacitors. Capacitors with fixed capacitance predominate in modern electronics. The main capacitor types of these are presented in the following overview: Capacitors with fixed capacitance Polarity: non-polar capacitors + – polar capacitors Capacitor type: Film capacitors Ceramic capacitors Electrolytic capacitors Super capacitors Fig. 1.