[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Xylo-SDR] A/D anti-aliasing filters
Why do I need a differential amplifier when I have a differential
source? That will only add noise. Each pair of the four integrating
capacitors are already 180 degrees out of phase from each other.
By not putting an amplifier in I'm trading off maximum signal level for
sensitivity. With 24 bits I believe the sensitivity is already below the
noise level for much of the HF bands (unless I goofed on the math).
The circuit in the TI data sheet is a combination single-ended to
differential converter, and a lowpass filter.
It's the filtering that I'm most worried about. Do I need more filtering
than the A/D and the integration capacitors provide? I guess I'm going
to find out, just wanted to reduce the number of prototyping cycles...
To get the rated performance from the 1804, you must interpose a
differential amplifier as outlined in the TI data sheet using very low
noise amplifiers. Not doing so will likely degrade the noise
performance of the part.