A 21 nV/$\surd$Hz Chopper-Stabilized Multi-Path Current-Feedback Instrumentation Amplifier With 2 $\mu$V Offset

Abstract

This paper describes the design of a precision instrumentation amplifier. It employs chopping to reduce its offset and 1/ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</i> noise, and the resulting ripple caused by the up-modulated offset and 1/ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</i> noise is suppressed by a ripple reduction loop. A multi-path architecture is used to eliminate the transfer function notch that would otherwise be introduced by the ripple reduction loop. The amplifier is implemented in a standard 0.7 μm CMOS technology and draws 143 μA current from a 5 V supply. Its input-referred noise is 21 nV/√Hz and its residual offset is less than 2× μV (12 samples). The instrumentation amplifier can also be configured as a general-purpose opamp with half the noise and offset, but which dissipates the same amount of power.