Chopper-stabilized Multipath Instrumentation Amplifier with Output Voltage Offset Compensation Using R-2R Digital-to-Analog Converter

This paper presents a 3-opamp resistive bridge sensor analog front-end (AFE) integrated circuit (IC) with offset voltage compensation using an R-2R digital-to-analog converter (DAC). The proposed IC is implemented with a 3-opamp instrumentation amplifier (IA) to achieve high gain, high input impedance, and linearity. The two amplifiers in the first stage are multipath amplifiers with a chopper stabilization technique and ripple reduction loop (RRL). The chopper stabilization technique reduces 1/f flicker noise and DC offset, and the RRL mitigates the output ripple voltage resulting from the chopper stabilization technique. The multipath amplifier scheme compensates the notch characteristic in the frequency response caused by the RRL. A fully differential amplifier with a class-AB output stage is used in the second stage to achieve power efficiency. The 12-bit R-2R DAC is implemented to compensate the offset of the second-stage output of the IA. The IA gain can be controlled from 12 to 48 dB using 2-bit and 3-bit programmable feedback resistor arrays in the first and second stages, respectively. The proposed IC is designed with a 0.18 μm complementary metal-oxide-semiconductor (CMOS) process and has an active area of 7.2 mm2. The simulated input-referred noise is 36.7 nV/√Hz at a frequency of 1 Hz and the simulated input offset voltage is 2.2 μV.