A Low noise chopper current feedback instrumentation amplifier

A low-noise instrumentation amplifier isproposed for biopotential signals acquisition. This circuit use a three-stage current feedback topology with miller compensation to achieve a high common-mode rejection ratio. A two-stage chopping structure is used to significantly reduce 1/f noise and DC offset. The output ripple introduced by the chopper switch is eliminated by implanting a second-order Sallen-Key low-pass filter. The circuit is designed in a SMIC 0.13 μm CMOS process with a current dissipation of 48μA at 1.2 V supply voltage, and the input reference noise power spectral density (PSD) is 26nV/rtHz, the noise efficiency factor (NEF) is 6.4 and the common mode rejection ratio is 114 dB. The simulation results show that at the first harmonic, the circuit reduce the high-frequency output ripple by a factor of 1/43.