A wide input range instrumentation amplifier for impedance spectroscopy applications

This paper presents a fully-differential instrumentation amplifier, designed for low voltage, integrated impedance spectroscopy systems. The proposed architecture combines relative simplicity with an almost rail-to-rail input range. A synchronous demodulator is embedded into the output stage. These characteristics make it suitable for AC current sensing applications. 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 error of nearly 1 % can be achieved for stimulation frequencies up to 1 MHz and with a DC input common-mode voltage variable across a nearly 1 V interval. Power consumption is 150 uW.