Switched-Capacitor Level-Shifting Technique With Sampling Noise Reduction for Rail-to-Rail Input Range Instrumentation Amplifiers

This paper proposes a switched-capacitor Adaptive Level-Shifting (ALS) technique for Instrumentation Amplifiers (IA). When used at the front end of an IA the ALS circuit enables true rail-to-rail input common-mode (CM) range and reduces CMRR requirements for the following IA. In the proposed implementation, two ALS circuits are combined with the two input stages of an Indirect Current-Feedback (ICF) IA. To overcome the limited input differential voltage range of such IAs, the ALS circuits are cross-connected. As a result the IA has a wide input differential range and a true rail-to-rail input CM range. The IA is fabricated in 0.18
$\mu{\hbox {m}}$
CMOS process, achieves 70
${\rm nV}/\surd{\rm Hz}$
noise spectral density, 115
$\mu{\hbox {A}}$
supply current, 20
$\mu{\rm V}$
input offset voltage, 130 dB CMRR and 20 ppm gain error.