I've been having trouble trying to design a bandpass filter, six pole that is centered at 25khz w/ 5khz. I was trying to do 6-pole low filter and 6-pole high filter and combine them. But it hasnt worked out. Please help.
If you have placed your knees at the correct frequencies, it should. What hasn't worked? Can you post up your work so we can see what might be giving problems?
I think all my analysis were wrong. So I just redesigned 6-pole low pass using the table(pole locations for each order, a+_ jb). Using multisim, i did ac sweep.
Could you tell me if I'm on right track here? Thank you guys.
The lousy old 741 opamp has trouble with frequencies above only 9kHz. The filter needs better opamps that work up to 90kHz. Many opamps work well up to 100kHz like the TL071 single, TL072 dual and TL074 quad opamps.
Yes, 741's are really obsolete and inadequate. Most manufacturers include the Spice parameters on their sites so you can see if another choice will work.
After redesigning the circuit, it's not working correctly still.
So I have 6-pole low pass and 6-pole high pass connected(Vout).
Looking at graph of AC sweep, it looks like low pass isnt' working correctly.
I've looking at this circuit for a while and couldn't figure it out.
Please help, any suggestions..thank you guys.
You are putting them parallel, this does not work.
Take a low-pass and a high passfilter and put them in series.
The low pass freq. = bandpass freq. + 1/2 bw
The high pass freq. = bandpass freq. - 1/2 bw
I'm having trouble changing cuttoff frequency.
Currently, it's at 10kHz and I'm trying to get 30kHz.
After calculation, and redesign, I realized that at 30khz,
there is a big spike right before cutoff frequency.
Any suggestions please. Thanks
for my redesign, I just divided all the resistors by 30.
I worked when i changed cutoff frequency at 1k to 10k.