Transimpedance instrumentation amplifier based on current inversion

This paper presents a novel instrumentation amplifier operating a differential current measurement from a resistive bridge. The proposed transimpedance instrumentation amplifier is constructed with two voltage opamps. One opamp is used to realize the current inversion and the second as a single input transimpedance amplifier. The resistive bridge is biased by a DC current and that it differs from the traditional voltage Wheatstone bridge. Simulation results by PSpice from a full custom 0.35μm CMOS opamp (BSIM transistor models) and the commercially LT1097 from linear technology (macro-model) show well performances of the proposed topology and confirm the validity of the circuit. Under ±2V opamps supply voltages, the CMOS full custom configuration consume 273μW per MHz and provides a linear sensitivity of 5mV/Ω.