fibean

modified 8 years ago

High Q factor active band pass filter

143

02:50:32

Band pass filter with a high Q factor. Frequency can be tuned by modifying the resistors and capacitors around the op-amp. There's also a simple detection circuit with can control a load or light up an LED when the input frequency matches the filter's.

published 8 years ago

hurz

8 years ago

High Q filter are very problematic

thebugger

8 years ago

Not unless you have a ultra high Q wide bandwidth filter. Check this breakthrough out http://www.iflscience.com/physics/the-solution-to-a-centuryold-physics-problem-might-lead-to-better-telecommunications-and-cloaking-devices/

hurz

8 years ago

Buggzy, have you read and understand the original article?

thebugger

8 years ago

Yes, that's a revised article, badly written at that.

hurz

8 years ago

I said "original" !

thebugger

8 years ago

Yes from the physics forum or something.

fibean

8 years ago

Why are they problematic? Frequency tuning?

hurz

8 years ago

For example, they are slow http://everycircuit.com/circuit/5572656000925696

thebugger

8 years ago

Yeah hurz is right they are slow, and also the higher the Q factor the less broader the bandwidth. With a high Q factor, a slight deviation in frequency will de-tune the circuit. Lower the Q factor a little.

hurz

8 years ago

Buggzy, how can you tell him to lower Q if you do not know what this filter is suppose for? Before you give advice to change anything, you have to understand the requirements!

thebugger

8 years ago

He wants to pass a single frequency over the output. He can use Low Pass - High Pass configuration to achieve it, although the slope will not be so steep. Or he can lower the Q very slightly, just enough to make it more stable. There are many compromises he can try. Also an LC filter might do him better, because inherently they have a steeper slope than RC filters.

hurz

8 years ago

Bla bla bla, and you know nothing, why are you doing this?

thebugger

8 years ago

I know you're an arrogant fuck, that's enough for me :)

hurz

8 years ago

What a foul mouth you are.

fibean

8 years ago

The circuit's purpose is to be a high Q band-pass filter. Even tough it's said to be slow, it acomplishes it's purpose as a high Q band-pass filter, so it stays as it is.

fibean

8 years ago

Thank you for the input guys. I'm sure this filter is not a "one size fits all" solution as there's no such thing, but some applications (say, tone detection) might as well benefit from this design. I want to share the circuit so more people can get to know this topology. I'm not supporting it's use for any particular application tough.

hurz

8 years ago

Right, keep it as it is and dont follow frauds. If you are happy with your design then let it as it is. We do not know for what you have made it. Thats ok.

fibean

8 years ago

I made it to contribute to the community, actually. I found this circuit to be very interesting and it could be useful for someone.

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