commonmodebrus

Common-mode noise, often colloquially referred to as common-mode brus, is a type of electrical noise that appears identically on both conductors of a pair of signal lines. This is in contrast to differential-mode noise, which appears with opposite polarity on the two conductors. Common-mode noise is particularly problematic in electronic systems because it can affect the intended signal without being easily removed by typical differential filtering techniques.

Sources of common-mode noise are varied and can include electromagnetic interference (EMI) from external sources like power lines, motors, or radio transmitters. It can also be generated internally within a system due to switching power supplies, digital logic transitions, or ground loops. Ground loops are a significant contributor, where unintended current paths create voltage differences across different ground points, injecting noise onto signal lines.

Because common-mode noise is present on both signal wires relative to ground, it can be difficult to distinguish from the actual differential signal. Techniques to mitigate common-mode noise include the use of common-mode chokes, which present a high impedance to common-mode currents while allowing differential signals to pass. Proper grounding and shielding practices are also crucial in preventing its introduction and propagation. When designing sensitive electronic circuits, understanding and addressing common-mode noise is essential for signal integrity.