I was trying to synthesise a sine wave of good spectral purity from DDS AD9912, is it better to keep LT6603
as my reconstruction filter or design my own lowpass filter with probably ADA4899-1 which has quite good
THD response.Iam plannning to use a programmable resistance or use my own bank of parallel resistances
for low pass filter and choose corresponding resistance circuit using switches.
Iam looking to get a THD of around -70dB at 50MHz.
Is it possible to get this result and is my method effective?
Also when i design my lowpass filter ,should the dac output see high impedance? if so i have to put two
non inverting configurations at both outputs and connect both to a differential lowpass filter.
Is this how iam supposed to proceed
Thanks in advance