PCB for Common Mode Filter (EMI/RFI filter)

 9.60 Incl. VAT
 8.00 Excl. VAT

PCB for Common Mode filter (EMI/RFI Filter)

In stock (can be backordered)


Nowadays we use an enormous amount of Switched Mode Power Supplies (SMPS) equipped domestic appliances, industrial electrical consumers etc. in our everyday life. These appliances throw a great deal of RF hash which sneaks and disturbs the precious analogous networks of our audio equipment.

The unit proposed here is a Common Mode Filter which suppress EMI/RFI radiations.
Schematic of the unit can be seen below:

Common Mode Filter (EMI/RFI filter)
Schematic of Common Mode Filter (EMI/RFI filter)

The Common Mode Filter will deal with the high frequency pollution in the AC Mains Network.
It was inspired by the very successful “Felix project” (

In-depth explanation and examples of Common Mode Filters can be found here:

In the process of CMF simulation the following results were outlined:

– The damping resistors lower the spike in frequency response with approx. 20 dB

CMF without damping resistors
CMF without damping resistors
CMF with damping resistors

– Removing the load-side shunt capacitors (as supposed in the Fo-Felix version of the filter) will give us a smoother frequency response but the corner frequency is shifted to the higher frequencies approx. 25 times

CMF without load-side shunt capacitor

Board specifications:

Dimensions of PCB: 50×115 mm.
PCB type: FR4 1.6 mm.. Copper thickness: 70 um (2oz). Surface finish – Nickel Gold (ENIG).

The board is TWO-layer design which allows the PCB traces to be doubled on the TOP and BOTTOM layers thus doubling the current handling capabilities of the board. All current conducting traces are widened as much as possible which additional raise the max. handled current.
PCB has solder mask coating on top and bottom layer for best durability.
Silk screen with parts layout is placed on the top of the PCB.

PCB has following abilities:

– Shunt capacitors C1 – C4 are X2 type safety polypropylene capacitors. There are several mounting holes on PCB which allows users to combine capacitors with different lead spacings.
– C5, C6 – Y2 type safety polypropylene capacitors
– Common Mode Choke can be up to 20A rated one
– AC input/output connectors can be of the following types:
a) MOLEX 3- or 5-pins terminal blocks with lead spacing 5 mm.
b) 3-pins Terminal Blocks with lead spacing 7.62 mm.
c) 3-pins Barrier Terminal Blocks with lead spacing 10 mm.

All parts used are easily obtainable from big supplier stores (Mouser, Farnell, Digi-Key etc.) or via e-bay.

Note: the listing is for PCB only – pictures of assembled device is for information purposes only!

Schematic and parts list will be sent to the buyer’s PayPal address after purchase. If for some reason a different e-mail address must be used, note it in the process of checkout.

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PCB for Common Mode filter (EMI/RFI Filter)
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Weight 0.055 kg