A CMOS low-noise instrumentation amplifier using chopper modulation

This paper describes a low-power, low-noise chopper stabilized CMOS instrumentation amplifier for biomedical applications. Low thermal noise is achieved by employing MOSTs biased in the weak/moderate inversion region, whereas chopper stabilization is utilized to shift 1/f-noise out of the signal band hereby ensuring overall low noise performance.

The resulting equivalent input referred noise is approximately 7 nV/rootHz for a chopping frequency of 20 kHz. The amplifier operates from a modest supply voltage of 1.8 V, drawing 136 muA of current thus consuming 245 muW of power. The gain is 72.5 dB over a 4 kHz bandwidth. The inband PSRR is above 90 and the CMRR exceeds 105 dB.