Generally, SMD ferrites of a given size are characterized by:
- The RF impedance (typically specified @
100 MHz
)- Low impedance (e.g.
100 Ω @ 100 MHz
) do not filter EMI that well, but also distort your data signals less. Use them for high speed signals above 1 MHz
- High impedance ferrites, e.g.
1kΩ @ 100 MHz
, filter EMI really well but will distort any high speed signal. Use them for low speed signals below 1 MHz
- The current rating
- For data signals, you don’t need any form of high current rating. Generally, I would recommend to require at least
0.1A
of current rating to be able to handle soft short circuits - For power lines, use whatever power rating is suitable (the specified current +
20%
is typically fine)
- The DC resistance. This mostly only matters for power lines.
- Keep in mind to keep the ferrite cool by choosing the DC resistance so that the
As with most passive parts, LCSC generally has the lowest pricing if you buy a bunch of parts.
Keep in mind the expensive shipping, but since they are often 50 times cheaper (!) than other distributors, it might be worth it even if just ordering a reel of ferrites.
Signal ferrites
This section contains cheap SMD ferrite beads for < 1A
current rating.
Low impedance (<= 500Ω
):
High impedance (>= 500Ω
):
Power ferrites
This section contains cheap SMD ferrite beads for > 1A
current rating.
Low impedance (<= 500Ω
):
High impedance (>= 500Ω
):