help with filter design-urgent

**aruna1** · Nov11-09, 04:26 AM

hello guys I have to design a band pass filter for high quality audio crosoveer circuit.
following are the given condidtions

filter range : 3kHz - 20khz
stop band attenuation : 80dB/decade
distortion in pass band should be minimum

can someone tell me how to decide maximum pass band attenuation to get high quality audio output
thanks

P.S. friend told me that if we take maximum pass band attenuation as 3db filter qulity will decrease

**berkeman** · Nov11-09, 12:59 PM

Originally Posted by aruna1

hello guys I have to design a band pass filter for high quality audio crosoveer circuit.
following are the given condidtions

filter range : 3kHz - 20khz
stop band attenuation : 80dB/decade
distortion in pass band should be minimum

can someone tell me how to decide maximum pass band attenuation to get high quality audio output
thanks

P.S. friend told me that if we take maximum pass band attenuation as 3db filter qulity will decrease

What is the application? Why is it urgent? Are you thinking active or passive filter (or digital even)? What kind of distortion spec is "minimum"?

**aruna1** · Nov11-09, 01:43 PM

applicationn: audio cross over
urgent- i have to submit it friday
filter type:active
about distrotion:i have no idea

**berkeman** · Nov11-09, 01:47 PM

Originally Posted by aruna1

applicationn: audio cross over
urgent- i have to submit it friday
filter type:active
about distrotion:i have no idea

Okay, thread moved to Homework Help.

What do you know about active filter design? You must have some resources available for this homework assignment. What are the main topologies (polynomials) for active filters? Which one would you choose for this assignment, and why?

**aruna1** · Nov11-09, 01:51 PM

Originally Posted by berkeman

Okay, thread moved to Homework Help.

What do you know about active filter design? You must have some resources available for this homework assignment. What are the main topologies (polynomials) for active filters? Which one would you choose for this assignment, and why?

well i have some idea how to design this,and actually i desgned 4th order sellen key band pass filter considering maximum pass band attenuation as 3dB,
but then my friend told me with 3dB maximum pass band attenuation, filter will be poor quality.so all i need to know how to select value for maximum pass band attenuation

thanks

**berkeman** · Nov11-09, 02:23 PM

Originally Posted by aruna1

well i have some idea how to design this,and actually i desgned 4th order sellen key band pass filter considering maximum pass band attenuation as 3dB,
but then my friend told me with 3dB maximum pass band attenuation, filter will be poor quality.so all i need to know how to select value for maximum pass band attenuation

thanks

What textbook are you using? It sounds like you are not getting much information on the characteristics of various active filter topologies and applications. This chapter from a TI publication should be of help:

http://focus.ti.com/lit/ml/sloa088/sloa088.pdf

.

**aruna1** · Nov11-09, 02:35 PM

i use microelectronic circuits by sedra/smith biiok
here are slides based on it

(rename this file to .zip exension. i had t rename it to pdf so i can bypass file size limit)

**berkeman** · Nov11-09, 04:57 PM

ZIP files are discouraged here, since they can contain viruses. File name extension is similarly discouraged. Was the TI chapter of any help?

**aruna1** · Nov11-09, 08:26 PM

I'm still reading it