how to design butterworth IIR filter

[vead]

I want to learn how to design butterworth IIR filter with low pass and designed by Z transform method
what specification I need to design
I know below
1) cutoff frequency
2)stop band frequency
3)Ripple in pass band
4)Filter order

what specification I need to know to design filter?

 

[Arouse1973]

Is this a homework question. If so there is a section for this. if not then can you supply the missing data you say you have?
1) cutoff frequency
2)stop band frequency
3)Ripple in pass band
4)Filter order
5)Input voltages and impedance.
6)Output impedance

Do you want the filter to be active or passive. Most analogue filters are IIR but when you say IIR first thing that springs to mind is a digital filter.

Can you explain a bit more.
thanks
Adam