Does the DAC output require a filter? why?
Much like an ADC requires an anti-aliasing filter, a DAC needs an analog reconstruction filter.
Mathematically, the DAC transfer function is that of a zer-order hold function. This means that the output will contain the baseband signal and its images around Fs, 2fs, 3Fs and so on (Fs is the sampling frequency of the DAC). Unlike a digital signal, these images are shaped by the envelope of the SInc transfer function.
In order to filter out these images and recover the original analog data, an analog reconstruction filter (either low-pass or band-pass) is needed. In the time domain, the DAC output, although analog in nature, looks like the sample-and-held version of the analog data. The reconstruction filter smoothens out the edges and reconstructs the analog data.
Retrieving data ...