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Design >> Mixed-Signal Design >> Is the SNR/DR spec reasonable?
https://designers-guide.org/forum/YaBB.pl?num=1258754110

Message started by xuedashun on Nov 20^th, 2009, 1:55pm

Title: Is the SNR/DR spec reasonable?
Post by xuedashun on Nov 20^th, 2009, 1:55pm

In a class D amplifier
2 stage sigma delta modulator + driver + speaker
the input is analog signal

the spec is: SNR/DR min=85dB, -60dBFS

From my understanding, it's impossible for 2stage SDM to reach 80dB
SNR. If the SMD is used in classD, is the 85dB spec reasonable?, if
reasonable, why??

Thanks.

Title: Re: Is the SNR/DR spec reasonable?
Post by vivkr on Dec 11^th, 2009, 5:59am

xuedashun wrote on Nov 20^th, 2009, 1:55pm:

From my understanding, it's impossible for 2stage SDM to reach 80dB
SNR. If the SMD is used in classD, is the 85dB spec reasonable?, if
reasonable, why??

Thanks.

I think that would depend on the OSR. As a matter of fact, the first SDM I ever designed had an ideal SQNR of around 84 dB, and was second order if I recall correctly. Of course, the real SNR was a few dB lower as it was limited by thermal noise.

Regards,

Vivek