Thanks everybody.
About the opamp instability, I could agree but the enhancement is not so great. It reach about +6dB, so…
I don’t agree the digital filtering equalization.
The ADC is 8bit, so its dynamics is about 46dB.
Also the sampling rate is 72Ms/s, so -to avoid aliasing- we should be able to keep the signal as low as -46dB at fc/2=36MHz.
This is a constraint for the correct sampling: it is useless any further consideration if the ADC sampled signal is noisy. Any digital processing couldn’t repair/equalize that.
Assuming a nominal 15MHz of bandwidth (what’s HugeMan is supposed to obtain), it means that we should be able to have an analog section capable to cut in just one octave over 43dB!
This is not impossible, of course, but it is very hard to obtain (it is a over-16 poles lowpass filter), by keeping a decent flatness within the bandpass.
My deal is having a GOOD analog section, having a flat bandpass from 0 to 10MHz. As “flat” I mean less than -/+1dB.
Anyone of you knows how the analog section switches are closed upon the various settings?
That’s would be comfortable to simulate on a PC before touching any hardware part.
Cheers