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Choosing tunable filters

Question asked by avinash on Aug 10, 2011
Latest reply on Sep 7, 2011 by avinash

hi all,


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