Abstract

A continuous-time common-mode feedback (CMFB) circuit for low-power, area-constrained neural recording amplifiers is proposed. The proposed CMFB circuit is compact; it can be realized by simply replacing passive components with transistors in a low-noise folded cascode operational transconductance amplifier (FC-OTA) that is one of the most widely adopted OTAs for neural recording amplifiers. The proposed CMFB also consumes no additional power, i.e., no separate CMFB amplifier is required, thus, it fits well to low-power, area-constrained multichannel neural recording amplifiers. The proposed CMFB is analyzed in the implementation of a fully differential AC-coupled neural recording amplifier and compared with that of an identical neural recording amplifier using a conventional differential difference amplifier-based CMFB in 0.18 μm CMOS technology post-layout simulations. The AC-coupled neural recording amplifier with the proposed CMFB occupies ~37% less area and consumes ~11% smaller power, providing 2.67× larger output common mode (CM) range without CM bandwidth sacrifice in the comparison.

Highlights

  • Multichannel neural recording in vivo is an essential electrophysiology tool to understand brain activities [1,2]

  • To fairly compare the performance, two identical AC-coupled neural recording amTo fairly compare the performance, two identical AC-coupled neural recording ampliplifiers were implemented by using the circuits in Figures 1 and 2b where the same FCfiers were implemented by using the circuits in Figures 1 and 2b where the same folded cascode operational transconductance amplifier (FC-operational transconductance amplifier (OTA))

  • 2 Ptot includes the power consumption from all components in a neural recording amplifier, such as OTA, common-mode feedback (CMFB), and bias networks, 3 MIM capacitors are not included since the active circuit can be buried under the MIM capacitors

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Summary

Introduction

Multichannel neural recording in vivo is an essential electrophysiology tool to understand brain activities [1,2]. Since a CMFB circuit usually consists of a common-mode and gain an OTA for low-power operations It provides large output voltage excursion evensensor with high it results in additional power area consumption and it an impleand lowfeedback, supply voltage (those are common in and neural recordings), as well asbecomes immunity mentation overhead for multichannel. It reuses the source degeneration resistors used in the conventional lowSince a CMFB circuitFC-OTA usuallyfor consists a common-mode an OTA for power, low-noise neuralof recordings to realize sensor a CMFBand function, and feedback, it results in additional power and area consumption becomesmechanism an imple- of the does not need consumption. A compact CMFB circuit that does not require an additional OTA is presented It reuses the source degeneration resistors used in the conventional lowpower, low-noise FC-OTA for neural recordings to realize a CMFB function, and does not need additional power and area consumption. Fewer process variations and 2.67× wider output CM range

Proposed
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Simplified
Results and Discussion
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Out CM
Conclusions
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