Hey yall !
I've got quite the problem with an assignment related to designing a band-pass filter.

In the assignment i have to design a band-pass filter which filters out a specific frequency, 5 k Hz. I have uploaded a jpg of the circuit I'm using. The assignment spec gives the choice of using an inductor/coil with either 100 μH or 220μH. After choosing the coil with the inductance of 100 μH i used the equation, seen in the attachments, to calculate the capacitance.

The circuit works as intended but ....

As i re-read the assignment spec i discovered that the coil also has a "natural resistance" of 0.21 Ω resp. 0.43 Ω (for the coils with 100 μH and 220μH).
When i applied the resistance to the circuit the result was of course not at all as good as before.

So my question is ... What do i need to do in order to compensate for the resistance of the coil to get the "same" result as before introducing it ?

 

Post the assignment spec.

 

The assignment spec is not in English, which is why i didn't post it. What kind of additional information were you looking for ?

I Should say that i have tried finding an equation which takes the coils resistance in to consideration but so far i have been unsuccessful. I'm not sure if i need to redesign the circuit entirely or if adding some component is enough, like a opamp perhaps ?

 

The assignment spec is not in English, which is why i didn't post it.

You obviously speak English, and presumably the other language as well.

Post the English translation of the spec.

What kind of additional information were you looking for ?

The usual sorts of specs; allowable attenuation at the center frequency, required out of band attenuation, etc.

I Should say that i have tried finding an equation which takes the coils resistance in to consideration but so far i have been unsuccessful.

That shouldn't be too difficult.

I'm not sure if i need to redesign the circuit entirely or if adding some component is enough, like a opamp perhaps ?

No single passive component is going to fix the problem. You could add a fixed gain equal to the loss at the center frequency.

 

So my question is ... What do i need to do in order to compensate for the resistance of the coil to get the "same" result as before introducing it ?

It's been decades for me since I was in school. All real coils have some resistance which degrade their performance compared to ideal coil. If you are using a simulator, you may want to experiment with adding a "peaking capacitor" at various places to see if you can peak up the response a little.