invariance of SNR of a single-bit sigma delta modulator with comparator offset

[pankaj jha]

Hello everyone,
Can anyone tell me the reason for the invariance of SNR of a single-bit sigma delta modulator with comparator offset. ?? U can also suggest the necessary reference.

 

[yuvan]

Hi, quantizer being in the feed forward path, error in them is attenuated by the NTF. So, at frequency of interest the noise contribution should be less. And also since it is single bit Quantizer, the offset error compared to the quantization error is too low.

 

[pankaj jha]

Hi, quantizer being in the feed forward path, error in them is attenuated by the NTF. So, at frequency of interest the noise contribution should be less. And also since it is single bit Quantizer, the offset error compared to the quantization error is too low.

dear Yuvan,
u r absolutely correct about the quantizer being in the feedforward path and the offset error being noise shaped. But I am confused because the circuit level implementation of the SDM shows significant degradation in the SNR with comparator offset, whereas the MATLAB SIMULINK simulation shows complete invariance (even if the offset is set to 1V and higher, when my reference voltage is 1.225V). Can u suggest any reason for the same.??