I am designing a PoE (Power over Ethernet) application. My question is can I run 48V DC Voltage through a standard RJ45 Jack WITH Magnetics? or do I need one WITHOUT magnetics?

I am planning to use this one, would it work for DC Voltage? Amphenol: RJMG264413101NR, https://www.amphenol-icc.com/rj-magnetic1x1-rjmg264413101nr.html

My concern is that DC signals will not pass through with integrated magnetics.

  • \$\begingroup\$ That part is not PoE compatible, and most PoE sources will not turn the DC power on with that port connected. \$\endgroup\$
    – Whit3rd
    Feb 6, 2019 at 22:03

2 Answers 2


You can use a jack with integrated magnetics that is designed for PoE applications.

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  • \$\begingroup\$ When you say "designed for PoE", do you mean that standard RJ45 Connectors with integrated magnetics will not work? \$\endgroup\$
    – Neil Dey
    Feb 6, 2019 at 17:47
  • 2
    \$\begingroup\$ I don't think they're guaranteed to work (well) because the magnetics could saturate with DC current flowing. \$\endgroup\$ Feb 6, 2019 at 17:55
  • \$\begingroup\$ The issue I see is no voltage getting thru the magnetics. \$\endgroup\$
    – Neil Dey
    Feb 6, 2019 at 17:56
  • 1
    \$\begingroup\$ If you look at the schematics above, the DC is injected on the cable side of the magnetics (which means it should be isolated from the PHY power). It will have no trouble passing through the coils (they're copper wire), but of course it is not coupled from the PHY side. But DC current can affect the AC characteristics of a transformer. \$\endgroup\$ Feb 6, 2019 at 17:58
  • \$\begingroup\$ @SpehroPefhany If the DC is going through a center tap, wouldn't the flux on both sides of the winding cancel? \$\endgroup\$
    – Hearth
    Feb 6, 2019 at 19:47

You do not need the magnetics to be in the connector, but I have observed that it is a nice feature where space is constrained.

There are always magnetics with ethernet connection, but PoE capable magnetics have the middle points of its coils (don't remember the name) out as a pin, and are bulkier such that one can bias them and send current through them.

You can use a standard RJ45 and have the PoE capable magnetics on the board, soldered. This is a more price conscious choice, since one can drive both prices down individually pretty easily. (Compared to anything by Amphenol.)


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