Thanks a lot guys,
This is what i thought about the possible options in fromt of me. shoot your opinions with out any hezitation.

Basically I have an analog signal ranging from 0 to 20mv that i want to read from a microcontroller.

option 1:
find the best instrumentation op-amp (high cost)with accurate gain and an ADC to convert into digital signal.

option 2:
Find a good DAC (avg cost), produce analog to match with the source signal (use comparator to mach both signals)

option 3:
mix option 1 and 2, except that use low cost
op-amp as we are using the feed back to check the accuracy.

i would love to hear your views on this like you all did before,
thanks again

Ramesh Reddy

PS:I can't help, but say sorry about the quality of my english.