Hi everybody,
I'm reading about sigma delta adc, the basic theory. I've read about the first order modulator and now the second order, but I have a problem (maybe stupid) with a phrase of my book (Data Converters by F.Maloberti), when he describe the 'passage' from first order to second order. He says: "Better performances and features are secured by using two integrators around the loop thus forming a second-order modulator as shown in the conceptual scheme of Fig. 6.11 (a). Since the use of two integrators in a feedback loop can
cause instability, it is necessary to dump one of the two integrators by using one of the two options represented by the dotted lines of Fig. 6.11 (a)." (Fig. 6.11 (a) is attached) Why two integrators can cause instability? I can't see... Thank you very much!

Thanks for your answer!

I've read the stability of second order modulator on Temes' book but he talks only about the 'classic' configuration of the second order modulator.. where can I find a discussion about the modulator of mine figure? [i.e, a first order modulator with two integrators in series instead of one]
Thank you!

You're absolutely right! I didn't think about using continous techniques [like the L-transform] to analyze the stability but I tried to use the Z-transform, and that is a little more unfriendly to me.

Thank you very much!!