High precision bidirectional chopper instrumentation amplifier with negative and positive input common mode range

A current feedback instrumentation amplifier (CFIA) with extended common mode input voltage range is presented. Referred to input offset of 70µV is obtained firstly by using chopping and gain enhancement techniques in order to increase the DC gain and secondly by adding an offset reduction loop (ORL). The proposed circuit is implemented in a high voltage 0.5µm SOI technology. A common mode rejection ratio (CMRR) of 260dB has been obtained by using single ended three stage architecture with a common mode input voltage from −18V to 80V. The stability of the CFIA is ensured for a close loop gain of 20V/V.