R2R resistor network to do out of the signal generator and DAC out of the signal generator to produce the waveform is completely different, if the same, the production of DAC manufacturers do not need to exist,
Directly with a few resistance can produce a DAC, digital signals and analog signals if not isolated, the noise can not be eliminated, there is, FPGA I / O port drive capacity is limited, not every I / O The current generated by the mouth will be exactly the same, which is the reason for the instability of the waveform, 11bit and 14bit waveform generated by a great difference, I do not know if you have not carefully observed, 14 I / O port can not say that the resolution of 14bit , He also has a large number of data stored with the waveform has a great relationship.