Noise is a fact of life, especially in electronic circuits. But on our paper schematics and just as often our simulations, there is no noise. If you are blinking an LED on a breadboard, you probably don’t care. But if you are working on something meatier, handling electrical noise gracefully is important and simulation can help you. [Ignacio de Mendizábal] has a great piece on simulating EMC filters using LTSpice that can get you started.
There are many ways of classifying noise and [Ignacio] starts with common-mode versus differential noise, where common-mode is noise with current flowing in the same direction without regard to the circuit’s normal operation, and differential noise having currents that flow in the opposite direction of normal current flow.
The post shows how to model both types of noise and also covers how to model real-world circuit elements that will more accurately capture the behavior of a real filter. Armed with a good model of noise and some Bode plots, your filter design work will be much easier and robust.
EMC, or electromagnetic compatibility, is crucial for commercial devices. Testing is expensive, so the more you can work out in a simulation, the better. If you need a kick start on using LTSpice, we got you.