A novel architecture for current-feedback instrumentation amplifiers with rail-to-rail input range

This paper presents a fully-differential current-feedback instrumentation amplifier with rail-to-rail input common-mode (CM) voltage range. Gm mismatches due to input CM variations have been reduced exploiting an original common-modes equalization loop. Chopping modulation is adopted to improve the performances of the amplifier in terms of offset and low frequency noise, while the intrinsic low-pass transfer function of the amplifier is exploited for the reduction of the offset-ripple. A prototype has been designed using the UMC 0.18um MM/RF CMOS process. Simulations, performed with a supply voltage of 1.5 V, showed that a maximum relative gain error of nearly ±1.5 %, against rail-to-rail input CM voltage variations, can be achieved.