substracting 2.5V offset from the common voltage

[seyyah]

offset 2.5v

I have a differential pair of signal. They both swing around 5V to the ground. The differential voltage is 20mV at max. I need to make them swing around 2.5V with respect to the ground. I have only positive supply. Since the differential signal is low i could not decide how to do? What can you offer me that does not reduce the accuracy significantly. I tried to offset two channels separately by two opamps that are in differential amplifier configuration and one input is supplied with 2.5V but even small resistor tolerances affected the accuracy significantly. What can i do?? Thanks.

 

[Kral]

output 2.5v offset

seyyah,
Any instrumentation amplifier (IA)that has a separate "Ref" input, and is capable of single supply operation should work. See, for example, the Linear Technology LT1101. Just connect a 2.5V reference voltage to the "Ref" input of the instrumentation amplifier. This will shift the output by 2.5 V. Make sure that the IA has a common mode range of at least 5V plus the differential input voltage range.
Regards,
Kral