I’ve been trying to get this LP filter to close more but haven’t had any luck. What would one adjust to get the filter cutoff frequency lower?
You can shift frequency by scaling all the filter circuit's capacitors in the same ratio, or all the resistors in the same ratio, assuming the source impedance is low.
Larger R or C means lower frequency.
Larger R or C means lower frequency.
What have you tried?
Also, what connects to the 'free' ends of R3214 and R3215?
Do I have this right?
Kind regards,
Drew
Also, what connects to the 'free' ends of R3214 and R3215?
Do I have this right?
- Capacitors in series act like high-pass filters. Lower values would increase the cutoff frequency response, right?
- Capacitors to ground act like low-pass filters. Lower values would decrease the cutoff frequency response, right?
Kind regards,
Drew
Thank you, @Mark Tillotson !
So, regardless of the filter type (high pass or low pass), increasing capacitance decreases the cutoff frequency.
I did have to derive this once, but it was about 40 years ago. 🙄
Kind regards,
Drew
So, regardless of the filter type (high pass or low pass), increasing capacitance decreases the cutoff frequency.
I did have to derive this once, but it was about 40 years ago. 🙄
Kind regards,
Drew
I’ve tried a larger capacitor C375 thinking that would make the filter close more. I’m fine with the frequency when it’s open, I just wish it would get darker when closed all the way. From what I’m understanding here, it looks like I’d have to increase C374 and C375 by the same ratio to do that. That doesn’t seem correct as I don’t want to shift the whole frequency, just one end. Perhaps I did a poor job of implementing.
Yes, all C change together otherwise the response curve shape will change, not just the cutoff frequency.