Shown here is the simplified indirect current-feedback, or ICF, architecture. The ICF in-amp consists of two trans-conductance amplifiers, or G-m’s, which convert voltage to current, and a trans-impedance amplifier to convert the difference current back to a voltage. Feedback from Vout to FB forces the differential voltage between FB and REF equal to the differential voltage between plus IN and minus IN. The output voltage with the feedback connected as shown can be written as VOUT = (+IN – -IN)*(1 + R2/R1) + VREF.