DAC to Analog Filter to ADC As the order of filter needed for digital information gets higher, it takes longer to process and requires more memory. Maybe analog filtering could be of use here. I know that the words analog and high precision dont often appear in the same room together, but lets assume they do for the sake of this post.

Ok, so I suggest that when a higher order filter is needed the following linkage of devices could be implemented:

DAC > Analog Filter > ADC

My question regarding this are:


Has this linkage of devices been used before?
If so, where can I find literature on it?
If not, why do you think it hasn't been used? 


(Assume highly precise analog filters are being used)
You wouldn't normally do that because it isn't worth the cost (hardware.)

FIR filters get computationally very expensive if you need sharp cutoffs.

Digital IIR filters that provide the same cutoff as a long FIR are computationally very cheap.

An analog filter will be equivalent to a digital IIR.  

If an analog filter can provide the performance you need, then you are better off implementing a digital IIR filter.  It saves you the DAC/ADC parts and it saves you the mess of an additional analog section with its inherent instabilities and potential to pickup noise.

If the digital IIR that can provide the performance you need is unstable, then it is very likely that the equivalent analog filter will also be very difficult to make work correctly.