Choosing inductors for your application

[R_G_B_]

I want to design a narrow bandpass filter say 10% of the centre frequency of 100khz.

Problem is that when designing such a filter using passive components. The inductors are quite large at these frequency. Wire wound seem best suited for these frequency however  they are quite large. Ferrite multilayer inductors such as SMD type don't have the required quality factor. Also if I could find a inductor with a self resonate frequency close to the required centre frequency and use that as it would offer a high quality factor. I would like a high q inductor that has a smallest possible footprint suitable for the centre frequency 100khz as mentioned above any help will be appreciated.  Thanks I found the Following link which is useful to others on this forum as mentioned in the link it difficult to find small inductors for this frequency range.

https://www.ednasia.com/passive-filter-design-made-easy/

[Benta]

I want to design a narrow bandpass filter say 10% of the centre frequency of 100khz.

What does that mean? -6 dB? -12 dB? -100 db?

100 kHz is not difficult and absolutely doable for passive LC filters. But at which impedance?

The link you posted uses immense inductor values and miniscule capacitors. It's totally off, somehow.

Please be specific about what you need.

[PartialDischarge]

I would try to do it active,  if passive is the only way use this link https://rf-tools.com/lc-filter/

[tszaboo]

How much power (if any) do you want to pass through this filter?

[R_G_B_]

20k input impedance Low power say 100u watts. Roll off factor 60db per decade
40db would be ok. 3db 10% of the  centre frequency. I need  a narrow filter to help increase the signal to noise ratio. In order to Increase a signals detectability.  Small foot print PCB required. So I wanted smallest Inductors as possible.
To for on the board of 45mm X 25mm.

[jonpaul]

RGB: A great topic, but the EDN Asia article is not a fine reference.

 Suggest to study filter design and theory, many classic books and sites describe the specification and design of filters.

You can get commercially made BP filters eg from Mini-Circuits, they may have a 100 kHz BP, probably Zo 50 Ohm.

Bon Chance

Jon

[tszaboo]

20k input impedance Low power say 100u watts. Roll off factor 60db per decade
40db would be ok. 3db 10% of the  centre frequency. I need  a narrow filter to help increase the signal to noise ratio. In order to Increase a signals detectability.  Small foot print PCB required. So I wanted smallest Inductors as possible.
To for on the board of 45mm X 25mm.

You are much more likely in need of a common mode choke. See if you can place that into your circuit.
Try to avoid the X-Y problem, explain what you are trying to do.