question in multibit sigma delta modulator

[glacieryy]

Hi all,
I want to design a multibit MASH sigma delta modulator.I know in most case ,the multibit DAC is used in the last stage,but now I want to use multibit DAC in every stage and I know in the first stage I should use DEM to shape or average the nonliearty caused by DAC.

The question is how to decide the bit number of DAC in every stage.

Thanks in advance.

Best regards
glacier

 

[eldo]

The principle to choose the number of bits is to keep it as low as possible. An extra bit in the ADC will cost you more in quantizer, DEM and decimator etc.