🚀 go-pugleaf

I'm interested in doing fast A/D conversion.  I have a flash converter
that claims to be able to sample at up to 15Mhz.  I was thinking of
something more like 10 or 3 for my fastest sampling rate. (I can't go above
about 10 because of the speed of my static rams, and I'm also leary of
strange problems due to stray inductance/capacitance at high frequences.)
I have basicaly two worries about the liner front end to the A/D.  One is
that since I'm going to be sampeling at differnt raits, I need to have a
number of anti-aliasing filters.  If I sample at 10Khz, 100khz, and 10Mhz
the I'm still going to have the fastest filter have a cutoff somwhere
below 5Mhz.  How do I go about building such a beast?  I guess I could make
an active filter out of high frequence op amps, but that sounds expencive.
(I'm basicaly designing a "digital scope" front end for my computer.)
I didn't see any examples of such a low pass filter in the lit, so I was
wondering how real systems do this.  Also I have to come up with input
conditioning spoo.  ie The ranging and overvoltage protection parts of
the scope. (And Keeping the input impedance high!) Blah! Any sugestions on
opamps to use, filter design, other sneekey tricks.   Would be greatly
apriciated.  The reason I wanted to sample at different raits is that I'd
like to be able to view a full wave of a 1Hz signal without haveing to have
Megs of fast ram on board to hold the sample.  Oh!  I also have to rig up
a trigger generating circuit of some type aswel.  Looks like I'm going to
learn a lot from this prodject. Is there some trick where I could have
the analog filter cut off some where and then use a digital filter to
clean it up more from there?  I'm basical looking for best bandwidth/price
that I can squeeze out of this design.  Sugestions on any fascet of the
design would be much apriciated!   Thanks,   -Kurt