->. In case of opamp as comparator,(besides it drawbacks), wll give high/low if v1 not equal to v2. So what about vid now.

As I have read vid = Vout/A. A being very large, vid ~=0. Isn't it contradiction b/w two points.

->. Even in differential opamp with feedback,

Vo= (-Rf/R1)(v1-v2) //terms carry their usual meaning

if v1=v2, then above vout gets zero.(Obviously this don't happen, just some poor assumptions of mine, as I didn't get that concept till now).

Kindly help me to understand this.