The circuit model of a capacitor consists of a series resistive element representing the ohmic resistance of the conducting elements along with the dielectric resistance. This is called the equivalent, or effective, series resistance (ESR). The dielectric effects occur when AC signals are applied to the capacitor.
In both digital and analog electronic circuits a capacitor is a fundamental element. It enables the filtering of signals and it provides a fundamental memory element. The capacitor is an element that stores energy in an electric field. The circuit symbol and associated electrical variables for the capacitor is shown on Figure 1. Figure 1.
The capacitor may be modeled as two conducting plates separated by a dielectric as shown on Figure 2. When a voltage v is applied across the plates, a charge +q accumulates on one plate and a charge –q on the other. Figure 2. Capacitor model capacitor plates i = dq . And thus we have, dt
These subcircuits model a capacitor's self-resonant and series resistive behavior. More complex models can be created that mimic other non-ideal behaviors such as dielectric absorption, leakage and temperature effects. Some capacitor manufacturers provide SPICE models that include these effects.
It is a function of the geometric characteristics of the capacitor - plate separation (d) and plate area (A) - and by the permittivity (ε) of the dielectric material between the plates. Capacitance represents the efficiency of charge storage and it is measured in units of Farads (F).
Capacitors are energy storage devices that are essential to both analog and digital electronic circuits. They are used in timing, for waveform creation and shaping, blocking direct current, and coupling of alternating current signals, filtering and smoothing, and of course, energy storage.
A conventional capacitor stores electric energy as static electricity by charge separation in an electric field between two electrode plates. The charge carriers are typically electrons, The amount of charge stored per unit voltage is essentially a function of the size of the plates, the plate material''s properties, the properties of the dielectric material placed between the plates, and the separati…