How to make filter use cd4069 ?

(I think that's not the correct section for this post)

The CD4069 is 6 inverter cmos unbuffered gates, you can use as amplifier in linear region. First "polarize" the gate in Vdd/2 (high value feedback resistor between in and out, 1M typical), then measure the gain. remark: Is a trasconductance amplifier.

Depending the frequency and type of filter I don't think that's a better way to make a filter, except if you want "just lowpassing" with a large marge of cut frequency, ex: two signals 10Khz and 1MHz, your fcut may varie into 20Khz and 700Khz...

Try the other alternativas such as OPA and sallen-key structures

I see no benefit compared to OP filter designs using quad OPs, except for the cost. The design would be limited to negative feedback only structures and medium Q. Also 4069 unbuffered inverters draw considerable supply current in linear region when operated above Vdd of 5V.

there are tons of applications using the CD4069UB for analog applications especially in low cost consumer products, it draw very low current less than 1ma while in linear mode. just search cd4069ub in google