Hi,
In some product, the 1st stage is the differtial amp stage. In measuring some spec,like PSRR,output reffred noise, the test condition need "Inputs ac-grounded with Ci=1uF",

Is it to prevent the high freq noise coupled into the input?

Alos,do u think the "Inputs ac-grounded with Ci=1uF" means every diff input connect a Ci=2uF to ground,respectively? Or it means a Ci=2uF connected the two diff input directly? For the two caes, the cap value has two times difference.

Thanks