A Low Noise, Low Power Capacitor Chopper Instrumentation Amplifier in 40nm CMOS for Biological Signal Acquisition

A low noise capacitance-coupled chopper instrument amplifier for biological signal acquisition is presented. The chopper modulation technique is used to effectively suppress the 1/f noise of the circuit, and a positive feedback loop (PFL) is added to significantly improve the AC equivalent input impedance of the circuit. In addition, a DC servo loop (DSL) with selectable switching is added to eliminate the DC misalignment introduced by the electrodes up to 50mV. The instrumentation amplifier is realized in a 40nm CMOS process. The total current consumed at a 1.2V supply is 4μA. Simulation show that the CMRR and PSRR of the circuit are 87dB and 73dB respectively, and integration noise is 0.8μVrms in the range of 0.5 to 1kHz.