Common-Mode and EMI Filters for Power and Signals
Common-mode filtering, complete EMI filters and RF filter parts
This collection spans several physically different noise-control products: dual-winding SMD common-mode filters for signal or DC power lines, wound through-hole and toroidal chokes for power wiring, packaged AC mains EMI filter assemblies, a common-mode filter IC, and separate SAW, LC and ceramic RF bandpass, high-pass and low-pass filters. A few listings are single-winding PFC or audio chokes, not common-mode filters. Identify the unwanted noise path and the actual device type before comparing ratings.
What the products do
- SMD common-mode signal filters: TCM0605, MCZ1210, WCM2012, DLW31, DLW43 and related parts use multi-terminal coupled windings to attenuate common-mode interference. Their 40, 90, 360, 600 or 1,000 Ω labels, where provided, represent impedance at a specified frequency, not DC resistance. For USB or another high-speed interface, verify pin mapping, differential insertion loss, common-mode impedance curve, signal bandwidth, current and the actual manufacturer data; the package size or “USB” in a title does not establish protocol compatibility.
- Higher-current PCB and wound chokes: ACM7060, ACM9070, UU/UF, toroidal, nanocrystalline and three-phase choices serve different conductor counts, power levels and mechanical layouts. Check the selected variant's winding configuration, mH/µH inductance, impedance at relevant frequency, DCR per winding, rated current, heating, insulation, clearance and mounting dimensions. Do not apply a three-phase device to a single-phase design without a matching circuit specification.
- Complete AC EMI filter assemblies: Packaged single-phase audio/power-line filters and 4-stage modules combine components in a defined enclosure or board. They are not equivalent to a bare choke. Check verified line voltage, frequency, load current, leakage current, connection diagram, protective earth, mounting, approvals and application-specific safety requirements before installation. A seller's 110/220 V or wattage headline is not a universal wiring or safety approval.
- RF frequency-selective filters: TA0843A 2330 MHz and TA2244A 868 MHz SAW parts, 2350/2370 MHz coaxial and 371 MHz SMA bandpass assemblies, and HFCN, LFCW, LFCN and BFCV listings are chosen by passband, insertion loss, return loss, stopband rejection, impedance, connector or footprint and allowable RF power. They select RF frequencies; they are not replacements for two-line common-mode chokes.
- Other results: An ECMF02-series chip has its own pinout and circuit conditions. Raphaelite 10 H load/audio chokes and a FeSiAl PFC coil are single-purpose inductive components; one carburetor starter-valve “choke” is mechanical, not an electrical filter. Source listing claims such as “original” or named brands do not independently validate authenticity or certification.
Selection workflow
- Determine whether the problem is common-mode conducted noise, differential-mode noise, AC line emissions or a defined RF passband. A common-mode choke alone does not guarantee differential-mode filtering or regulatory compliance.
- For a line filter, document conductors, operating and surge voltage, current, frequency, safety class and physical connection. For an RF filter, document center frequency, bandwidth, characteristic impedance and losses.
- Compare the selected device's test conditions: impedance versus frequency is not inductance or DCR; 1 mH equals 1,000 µH. Verify insertion loss and thermal behavior in the actual circuit rather than extrapolating a headline number.
- Match variant-specific dimensions, terminal arrangement and pack quantity, and consult verified datasheets for any safety- or signal-integrity-critical design.
FAQ
Can a 90 Ω SMD common-mode filter be swapped for another 90 Ω part? Not on that number alone. Frequency response, differential loss, current, pinout and footprint may differ.
Is a complete AC EMI filter the same as an inductor? No. An assembly may include capacitors and other components, with distinct wiring, leakage and safety requirements.
Will a SAW bandpass filter remove common-mode noise from a power line? No. It is an RF frequency-selective component for its specified impedance and passband.
