Highly sensitive biomedical amplifier with CMRR calibration and DC-offset compensation

To cover a wide range of biomedical applications, the presented instrumentational amplifier (INA) for acquisition of biomedical signals is adjustable regarding power consumption and noise. In addition, DC-offsets larger than plusmn500 mV resulting from electrochemical potentials of the electrodes can be compensated by applying a voltage to an additional input. To achieve a high common mode rejection ratio (CMRR) of more than 80 dB, a digitally controlled calibration circuitry has been integrated. The novel concept of calibrating the CMRR in the high resistive feedback loop of an opamp and the DC electrode potential suppression does not require any external components. The INA has been fabricated in a 350 nm CMOS technology.