Re: error integrator
If you upload your schematic we can better hep you.
Anyway, by using an integrator in your feedback loop reduces you input offset with respect to a given reference. As it is connected so that the ouput of the main amplifier is compared to a given reference and this diference is integrated and fed back to an auxiliary input of the main amplifier, the effective offset at the output, that is the input offset of the integrator, is divided by the gain of the main amplifier.
On the other hand, an integrator connected like that places a zero at DC in your overall frequency response.
See attach