HI Christopher,
Thanks for your help.
1- VCOM= 2.5V. If i apply Ain+ = 3.28V and Ain- = 1.66V I have Vout+ = 2.92V and Vout- = 2.06V
2- Yes i have external +-10V supplies to the MMB0
3-J13 is set according to figure 5 in User's guide
it still doesn't explain the 0.5 gain
Yannick