Noise Analysis of Current-Feedback DC-Servo Loop in Current-Balancing Chopper Amplifiers

Biopotential acquisition chopper instrumentation amplifiers require a dc-servo loop (DSL) in order to filter electrode dc offsets. However, the noise performance degradation due to the addition of the DSL is often overlooked despite that it can be very detrimental at the frequencies of interest. This article presents an in-depth noise analysis of biopotential acquisition chopper instrumentation amplifiers with analog DSLs. Analytical expressions that predict the noise of different DSL implementations are found and a design flow to minimize their noise contribution is proposed. The design methodology is demonstrated with example circuits targeting biopotential recording systems. These circuits are implemented using a standard 180 nm CMOS technology, and their performance is verified through postlayout simulations. The findings of this work provide a comprehensive understanding of the noise characteristics of a DSL, its impact on noise performance, and design strategies for noise optimization.

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A chopper amplifier with adaptive biasing OTA for biomedical applications, featuring high gain and CMRR

Kasipogula,

Komanapalli

2024

PLoS ONE

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This paper presents a design of fully differential chopper amplifier employing the flipped voltage follower (FVF) adaptive biasing technique, focusing on its potential use in biopotential recording applications. The suggested architectural OTA incorporates self-cascoded current mirrors (SCCMs) as the active load to achieve a substantial output swing. The FVFs based adaptive biasing approach for the differential input stage boosts extra current and enhances gain and dynamic characteristics. The chopper amplifier attains a common mode rejection ratio (CMRR) of more than 100 dB through the strategic utilization of chopper modulators and pseudo-resistors. Additionally, this device exhibits characteristics such as accurate and stable gain, high input impedance, and a compact physical footprint. The present study also includes a comparison between the suggested structure and the bio-potential amplifiers discussed in the existing literature. This comparison is based on key metrics such as gain, input referred noise (IRN), CMRR, and input impedance (Zin). The proposed structure yielded a gain of 63.72 dB, an IRN of 0.07nVrms, a CMRR of 127.97 dB and a Zin of 1.54 GΩ. The bio-potential chopper amplifier under consideration was constructed and simulations were performed by utilizing the Cadence Virtuoso Spectre simulator tool at 180 nm CMOS technology node.

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Noise Analysis of Current-Feedback DC-Servo Loop in Current-Balancing Chopper Amplifiers

Cited by 3 publications

References 9 publications

A Capacitively Coupled Chopper Instrumentation Amplifier With Compensated Auto-Zeroed DC Servo-Loop for Neural Signal Recording

A Capacitively Coupled Chopper Instrumentation Amplifier With Compensated Auto-Zeroed DC Servo-Loop for Neural Signal Recording

Noise Analysis and Design Methodology of Chopper Amplifiers With Analog DC-Servo Loop for Biopotential Acquisition Applications

A chopper amplifier with adaptive biasing OTA for biomedical applications, featuring high gain and CMRR

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