Simple Explanation of Capacitor ESR – Why Is It Important and How Is It Specified?

投稿人:DigiKey

Equivalent series resistance (ESR) (represented by Resr­ in Figure 1) describes losses associated with moving charge through a capacitor.  The resistance of the electrode and lead materials is a contributing factor, and losses occurring within the dielectric material itself also occur and are often dominant.  The relevance of ESR to capacitor selection is twofold: 1) it influences the AC response of the capacitor, and 2) it imposes limits on the amount of AC current that can be permitted to flow through the capacitor due to thermal limitations.  Current flow through a capacitor’s ESR results in I2R losses just like any other resistor, causing a temperature increase within the capacitor that contributes to diminished device longevity.

ESR is influenced by device type and construction, and also by temperature and test frequency to varying degrees.  In many cases, the ESR of a capacitor is not directly given in a datasheet, but rather communicated in terms of a summary figure such as Q, dissipation factor (DF), or Tan δ.  All are quotients of a capacitor’s ESR and capacitive reactance (XC) expressed differently.  Tan δ and dissipation factor are calculated as ESR/XC, and are essentially the same figure, though it should be noted that dissipation factor is usually expressed as a percentage, rather than as a simple dimensionless factor. Q is simply the reciprocal of Tan δ, or XC/ESR.

More information on the non-ideal properties of capacitors can be found here.

Image of ideal capacitor should in reality be modeled as shown

Figure 1:  An ideal capacitor (left) should in reality be modeled as shown (right).

DigiKey logo

免责声明:各个作者和/或论坛参与者在本网站发表的观点、看法和意见不代表 DigiKey 的观点、看法和意见,也不代表 DigiKey 官方政策。

关于此出版商

DigiKey

DigiKey 总部设在美国明尼苏达州锡夫里弗福尔斯市,是一个同时针对原型开发/设计提供小批量供应、针对生产提供大批量供应的全球电子元件综合服务提供商,在 DigiKey 上提供 750 多家优质制造商品牌、六百多万种产品。