Title :
Auto Correction Feedback for Ripple Suppression in a Chopper Amplifier
Author :
Kusuda, Yoshinori
Author_Institution :
Analog Devices, Inc., Wilmington, MA, USA
Abstract :
This paper proposes a local feedback, named Auto Correction Feedback (ACFB), for a chopper amplifier to suppress its offset related ripple. It nulls out the amplifier´s initial offset in DC domain which would otherwise become modulated ripple at the chopper amplifier´s output, instead of filtering the ripple with a post filter. The proposed ACFB has been implemented as a stand alone chopper operational amplifier fabricated in 0.64 mm2 die area with a 0.35 μm standard CMOS process. It achieves 10 μV maximum input offset voltage and 95 nV/rt(Hz) input voltage noise spectrum density flat down to 0.1 Hz, with a 1.8-5.5 V supply voltage range and 13 μA supply current dissipation. When configured in unity-gain, the typical magnitude of the input referred ripple at the chopping frequency is 9.4 μVrms, as a result of 45 dB ripple attenuation obtained by the ACFB. The analysis, the simulation, and the measurement prove there is no noise penalty due to the addition of ACFB.
Keywords :
CMOS analogue integrated circuits; choppers (circuits); circuit feedback; circuit noise; operational amplifiers; CMOS process; DC domain; auto correction feedback; chopper operational amplifier; current 13 muA; current dissipation; local feedback; ripple suppression; size 0.35 mum; voltage 1.8 V to 5.5 V; voltage 10 muV; voltage noise spectrum density; Attenuation; CMOS process; Choppers; Current supplies; Feedback; Filtering; Filters; Frequency; Operational amplifiers; Voltage; CMOS operational amplifier; Chopper; local feedback; low noise; low offset; low power dissipation; ripple suppression; switched capacitor filter;
Journal_Title :
Solid-State Circuits, IEEE Journal of
DOI :
10.1109/JSSC.2010.2048142
