Measurement and Analysis of Current Noise in Chopper Amplifiers
J Xu (Holst Centre)
Q. Fan (TU Delft - Microelectronics)
Johan H. Huijsing (TU Delft - Electronic Instrumentation)
Chris van Hoof (IMEC)
RF Yazicioglu (IMEC)
Kofi A.A. Makinwa (TU Delft - Electronic Instrumentation)
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Abstract
This paper presents a theoretical analysis and measurements of the current noise of several chopper instrumentation amplifiers, which demonstrate that the charge injection and clock feed-through associated with the MOSFETs of the input chopper give rise to significant input current and current noise. In combi-
nation with high source impedances, this “chopper noise” is converted to voltage noise, which may then be a significant contributor to the amplifier’s total input-referred voltage noise. Chopper noise has a white power spectral density, whose magnitude is roughly proportional to the chopping frequency. Design guidelines are proposed to reduce chopper noise, as well as the use of a clock-boot-
strapped chopper, which generates significantly less noise than a traditional chopper.