Does a ceramic filter have polarity?

[avz]

I've a kit of a circuit from Aliexpress (China). one of the components is a three leg ceramic filter, I understand that they are input, gnd and output. on one side, upper left, there is red dot. since I never dealt with it before, I would like to ask if there is a polarity to it and if so, what it is? I've tried to find the answer on the web but I found contradict information (at least that's what I think). in some places it seems that the red dot donates the output and on other places -just the opposite.
Thanx.

 

[JimB]

a three leg ceramic filter, I understand that they are input, gnd and output.

Correct.

if there is a polarity to it and if so, what it is?

There is no "polarity" as such, but depending on the exact filter, it may have been designed for different input and out impedances in the external circuitry.

A quick read of the Murata application notes,

https://www.murata.com/~/media/webrenewal/support/library/catalog/products/filter/cerafil/p11e.ashx

Murata make probably more ceramic filters that anyone else, suggests that the input and output impedances are designed to be the same.

For your filter, I suggest that you put the dot at the input and call it good.
Nothing bad can happen, you will not cause a discontinuity in the space-time continuum. (Worst case scenario.).

JimB

 

[Beau Schwabe]

The hard to find now 455B's do have a "impedance" polarity as mentioned above.

 

[avz]

Thanx for your replies. I don't know if it matters, but the filters frequency is 10.7Mhz.

 

[Nigel Goodwin]

Thanx for your replies. I don't know if it matters, but the filters frequency is 10.7Mhz.

Don't worry about it - it's VERY, VERY unlikely to be polarised - interesting that Beau Schwabe actually managed to find an old one that was.

 

[Beau Schwabe]

I did find in a datasheet that it should not matter if the input and outputs are swapped.

Reference Datasheet page 8:

However in practice I have observed this to not always be true.

Reference Datasheet:

https://www.murata.com/~/media/webrenewal/support/library/catalog/products/filter/cerafil/p11e.ashx