What is a common characteristic impedance for all category/class rated cables?

The common characteristic impedance for all category and class-rated cables is 100 ohms. This value is particularly significant for balanced twisted pair cables, such as those that fall under the categories defined by TIA/EIA standards, including Cat 5e, Cat 6, Cat 6A, and others.

The 100-ohm impedance is crucial for ensuring effective signal transmission and minimizing reflections that can lead to data loss or degradation in performance. This impedance level is optimal for the operation of Ethernet and other networking technologies that utilize these types of cables, aligning with the electrical properties of the cable structure.

In contrast, other characteristic impedances like 50 ohms or 75 ohms are commonly used in other applications, such as coaxial cables. For instance, 75 ohms is standard in cable television and some video applications, whereas 50 ohms is typically used in RF (radio frequency) applications. 150 ohms is not a standard characteristic impedance for common data communications cabling, making 100 ohms the appropriate choice for category and class-rated cables.