A Fully Differential Chopper Circuit in 130nm CMOS for Noise Minimization in Sensor Applications

Abstract

For sensor applications, the bandwidth of interest is generally a few hertz. In this bandwidth, offset and 1/f noise are the dominant sources of error. Chopping technique is an efficient approach to decrease the 1/f noise and low-frequency offset of CMOS amplifiers; thus, in this paper, a proposed chopper circuit to tackle these problems is presented. The chopper circuit is designed using complementary CMOS switches that are optimized to achieve symmetric linear resistance in the range of input signal. The proposed circuit has a low ON resistance that only varies within 8% of its value for a rail to rail input. To validate its operation, it is used to build up a fully differential chopper stabilized CMOS amplifier powered at 1V. The resulting circuit achieves a thermal noise floor of 10 nV/√Hz and reduces the input referred noise corner frequency from 1-kHz to300mHz.