# Ferrite Beads Overview Links: [[Ferrite Bead Fundamentals (EEforEveryone)]] [[Ferrite Beads (w2aew)]] [[Ferrite Beads in Power Electronics (Sam Ben-Yaakov)]] [[Ferrite Core Essentials for EMC Test Engineers (Mach One Design EMC)]] ###### Overview - Ferrite beads are different from Inductors and Chokes - Inductors are physically larger and have narrower frequency bands - Used to suppress HF noise in power lines on PCBs - Acting as frequency-dependent resistors - Dissipate HF noise as heat. ###### Selection - Impedance is usually specified at 100MHz - Max Current Rating must be considered to ensure bead does not saturate under normal operating conditions - Consider DC resistance to minimize efficiency losses ###### Buddy Capacitor Choice - Low ESR is important for effective noise shunting - A combination of different capacitors in parallel to address different frequencies is common ###### Ferrite Beads vs. Inductors - Energy - Ferrite beads are designed for **energy dissipation** and have a higher resistive component to their impedance at high frequencies. - Inductors are designed for **energy storage** and minimize the resistive aspect to minimize dissipation. - Frequency - Ferrite Beads are designed for broadband HF impedance - Inductors are designed for resonance at specific frequencies ###### Ferrite Beads in Under a Minute - [Link](https://www.youtube.com/shorts/SApjHiu8eoo?feature=share) - A Ferrite Bead can be considered a "Lossy Inductor" - A "ZRX Chart" is the most important thing in every Ferrite Bead Datasheet. - Each Ferrite Bead will have an Inductive, Resistive, and Capacitive Range. - You want the noise you are filtering to fall into the Resistive Range. - The amount of current running through the Ferrite Bead reduces its impedance - Try not to exceed 20-30% of the current rating for optimal performance - If you're seeing a bandwidth peak due to resonance with the following capacitor, you can add a high ESR capacitor in parallel to smooth things out. ![[Pasted image 20241214080337.png]] ![[Pasted image 20241214080255.png]] ##### Additional Notes Ferrite Beads take HF noise and prevent it from radiating into the environment or disturbing circuits. Really, it's taking that HF energy and converting it into waste heat. It's going to release that energy into the world either way. You're just choosing to change it from RF chatter into waste heat beforehand. It costs some companies hundreds of thousands of dollars to send their equipment to EMI/EMC test labs to get CE compliance certs. Some people don't like Ferrite Beads in audio applications due to the linear Impedance-Frequency relationship. Preference is thicker cables, better shielding, etc. You don't want Impedance necessarily. You want low noise. Ferrite Beads serve the purpose of creating high impedance that can block/delete noise. ##### Parts and Datasheets ###### Some Part Examples ![[Pasted image 20241214125217.png]] ###### Parsing the Component Code ![[Pasted image 20241214125403.png]] ###### Some ZXR Charts ![[Pasted image 20241214125501.png]] ###### LTSpice Component Libraries ![[Pasted image 20241214125758.png]] ###### TDK Equivalent Circuit Model for Ferrite Beads ![[Pasted image 20241214130211.png]] ![[Pasted image 20241214131721.png]] https://product.tdk.com/en/search/emc/emc/beads/info?part_no=MPZ2012S102ATD25&utm_source=beads_automotive_power_mpz2012_en.pdf&utm_medium=catalog