Abstract
This chapter investigates the root cause of 1/f 2 noise of chopper amplifiers through a theoretical analysis and measurements of several chopper IAs. It is well known that the charge injection and clock feedthrough associated with the MOSFETs of the input chopper give rise to significant input current and current noise, which may then be a significant contributor to the amplifier’s total input-referred voltage noise. Furthermore, the chopper noise has a white power spectral density, its magnitude is roughly proportional to the chopping frequency. Design guidelines are proposed to reduce the chopper noise. A further proposal is the use of a clock-bootstrapped chopper, which exhibits less noise than a traditional chopper.
This chapter is derived from a journal publication of the authors: J. Xu, Q. Fan, et al., “Measurement and Analysis of Current Noise in Chopper Amplifiers” IEEE J. Solid-State Circuit, vol.48, no.7, pp. 1575–1584, July. 2013.
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Xu, J., Yazicioglu, R.F., Van Hoof, C., Makinwa, K. (2018). Current Noise of Chopper Amplifiers. In: Low Power Active Electrode ICs for Wearable EEG Acquisition. Analog Circuits and Signal Processing. Springer, Cham. https://doi.org/10.1007/978-3-319-74863-4_5
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