Why first order modulator limited to 1-bit quantizer?

[neoflash]

first order modulator

Why it can't use multi-bit quantizer?

Thanks.

 

[sumit_techkgp]

You can use a multibit quantizer. Where are u using, it depends on that!. What is the application ?

 

[neoflash]

It is for fractional-n sythesizer. Does it matters?

 

[sumit_techkgp]

U have a DAC. One bit DAC is a simple switch. More than one bit involves nonlinerity. Thats the reason. One bit circuit has lesser nonlinearity.

 

[mike_bihan]

This says it is a soft limitation and not a hard one. We can still go multi-bit quantizer in 1st order MOD, at the cost of higher non-linearity, right?

Added after 1 minutes:

U have a DAC. One bit DAC is a simple switch. More than one bit involves nonlinerity. Thats the reason. One bit circuit has lesser nonlinearity.

by the way, the sigma-delta modulator is in digital domain for frequency synthesizer, so there is no limitation on DAC linearity.