Päätevastus

Päätevastus, also known as a terminating resistor or termination, is a resistor placed at the end of a transmission line or bus. Its purpose is to absorb the signal energy, preventing reflections that can distort the signal. Without proper termination, signals traveling down a transmission line can bounce back and forth, creating noise and interfering with the data being transmitted. This is particularly important in high-speed digital systems and long cables where signal integrity is critical.

The value of a päätevastus is typically matched to the characteristic impedance of the transmission line. This impedance is a property of the line itself, determined by its physical construction, such as the width of the conductors, the distance between them, and the dielectric material used. By matching the resistor's value to the line's characteristic impedance, the signal encounters a consistent impedance at the end of the line, allowing it to be absorbed rather than reflected.

Common applications for päätevastus include Ethernet networks, where they are used in bus topologies and at the ends of longer cable runs. They are also found in video transmission systems and other high-frequency communication interfaces. The use of appropriate termination is a fundamental principle in designing reliable and high-performance electronic systems. Incorrect termination can lead to intermittent errors, data corruption, and overall system instability.