This is a great filter, easy to use. I tested it out (the '294 - which has steepest cutoff) and it works exactly as specified ! I set the clock to 400Khz, and sure enough at 4Khz it started dropping off, and by 4.8Khz the signal was lost in the noise which was around 60dB below.
The only downside is the data sheet restriction on input signal being between +1 to +4v. I tested it for lower signals - down to 100mV, which still worked. But of course the Noise levels started spoiling the output. Also there IS a clock feedthrough of around 5mV, so a post filter can be used if this is a problem.
