delta sigma modulator-- is the same used in ADC and DAC

pianomania · Mar 22, 2011

is the modulator the same used in delta sigma ADC and DAC ?

for example if the 2nd order dsm used in DAC has the same transfer function as ADC ?

and how about the second order ?

and is the implementaion method the same?

fcfusion · Mar 22, 2011

Theoretically, ADC and DAC Sigma-Deltas are identical:both consist of cascaded integrators, a quantizer and a feedback loop. Therefore, in theory the transfer function remains the same in both cases. They can even use the same coefficients.

However, implementation is a completely different case. ADC Sigma-Deltas have an analog input and digital output and therefore are usually implemented with continuous time RC integrators or discrete-time switched capacitor integrators and the quantizer is a comparator.
DAC SDM are generally digital circuits with an analog output circuit such as a Direct Charge Transfer or a filtered Bridge Tied Load.

Real transfer functions are a bit different for DAC and ADC, since the implementation is different as well.

pianomania · Mar 23, 2011

fcfusion said:
Theoretically, ADC and DAC Sigma-Deltas are identical:both consist of cascaded integrators, a quantizer and a feedback loop. Therefore, in theory the transfer function remains the same in both cases. They can even use the same coefficients.

However, implementation is a completely different case. ADC Sigma-Deltas have an analog input and digital output and therefore are usually implemented with continuous time RC integrators or discrete-time switched capacitor integrators and the quantizer is a comparator.
DAC SDM are generally digital circuits with an analog output circuit such as a Direct Charge Transfer or a filtered Bridge Tied Load.

Real transfer functions are a bit different for DAC and ADC, since the implementation is different as well.

thank for your reply ,
and if the direct charge transfer means the switch cap filter or charge pump ?

ic98 · Mar 24, 2011

They're not identical, have look at schreier's book on delta-sigma design & analysis.

delta sigma modulator-- is the same used in ADC and DAC

pianomania

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