A Sub-µW Reconfigurable Front-End for Invasive Neural Recording

This paper presents a sub-μW ac-coupled reconfigurable front-end for the purpose of neural recording. The proposed topology embeds in it filtering capabilities allowing it to select among different frequency bands inside the neural signal spectrum. Power consumption is optimized by designing for bandwidth-specific noise targets that take into account the spectral characteristics of the input signal as well as the noise bandwidths of the noise generators in the circuit itself. An experimentally verified prototype designed in a 180 nm CMOS process draws a maximum of 815 nW from a 1 V source. The measured input-referred spot-noise at 500 Hz is 75 nV/√Hz while the integrated noise in the 200 Hz - 5 kHz band is 4.1 μVrms.Ministerio de Economía y Competitividad TEC2016-80923- PJunta de Andalucía TIC 233

Amplifiers in Biomedical Engineering: A Review from Application Perspectives

Continuous monitoring and treatment of various diseases with biomedical technologies and wearable electronics has become significantly important. The healthcare area is an important, evolving field that, among other things, requires electronic and micro-electromechanical technologies. Designed circuits and smart devices can lead to reduced hospitalization time and hospitals equipped with high-quality equipment. Some of these devices can also be implanted inside the body. Recently, various implanted electronic devices for monitoring and diagnosing diseases have been presented. These instruments require communication links through wireless technologies. In the transmitters of these devices, power amplifiers are the most important components and their performance plays important roles. This paper is devoted to collecting and providing a comprehensive review on the various designed implanted amplifiers for advanced biomedical applications. The reported amplifiers vary with respect to the class/type of amplifier, implemented CMOS technology, frequency band, output power, and the overall efficiency of the designs. The purpose of the authors is to provide a general view of the available solutions, and any researcher can obtain suitable circuit designs that can be selected for their problem by reading this survey

Advances in Microelectronics for Implantable Medical Devices

Implantable medical devices provide therapy to treat numerous health conditions as well as monitoring and diagnosis. Over the years, the development of these devices has seen remarkable progress thanks to tremendous advances in microelectronics, electrode technology, packaging and signal processing techniques. Many of today’s implantable devices use wireless technology to supply power and provide communication. There are many challenges when creating an implantable device. Issues such as reliable and fast bidirectional data communication, efficient power delivery to the implantable circuits, low noise and low power for the recording part of the system, and delivery of safe stimulation to avoid tissue and electrode damage are some of the challenges faced by the microelectronics circuit designer. This paper provides a review of advances in microelectronics over the last decade or so for implantable medical devices and systems. The focus is on neural recording and stimulation circuits suitable for fabrication in modern silicon process technologies and biotelemetry methods for power and data transfer, with particular emphasis on methods employing radio frequency inductive coupling. The paper concludes by highlighting some of the issues that will drive future research in the field

Integrated circuit design for implantable neural interfaces

Progress in microfabrication technology has opened the way for new possibilities in neuroscience and medicine. Chronic, biocompatible brain implants with recording and stimulation capabilities provided by embedded electronics have been successfully demonstrated. However, more ambitious applications call for improvements in every aspect of existing implementations. This thesis proposes two prototypes that advance the field in significant ways. The first prototype is a neural recording front-end with spectral selectivity capabilities that implements a design strategy that leads to the lowest reported power consumption as compared to the state of the art. The second one is a bidirectional front-end for closed-loop neuromodulation that accounts for self-interference and impedance mismatch thus enabling simultaneous recording and stimulation. The design process and experimental verification of both prototypes is presented herein

An AC-Coupled Wideband Neural Recording Front-End With Sub-1 mm² × fJ/conv-step Efficiency and 0.97 NEF

This letter presents an energy-and-area-efficient ac-coupled front-end for the multichannel recording of wideband neural signals. The proposed unit conditions local field and action potentials using an inverter-based capacitively coupled low-noise amplifier, followed by a per-channel 10-b asynchronous SAR ADC. The adaptation of unit-length capacitors minimizes the ADC area and relaxes the amplifier gain so that small coupling capacitors can be integrated. The prototype in 65-nm CMOS achieves 4× smaller area and 3× higher energy–area efficiency compared to the state of the art with 164 μm×40μm footprint and 0.78 mm²× fJ/conv-step energy-area figure of merit. The measured 0.65- μW power consumption and 3.1 - μVrms input-referred noise within 1 Hz–10 kHz bandwidth correspond to a noise efficiency factor of 0.97

An AC-Coupled Wideband Neural Recording Front-End With Sub-1 mm² × fJ/conv-step Efficiency and 0.97 NEF

This letter presents an energy-and-area-efficient ac-coupled front-end for the multichannel recording of wideband neural signals. The proposed unit conditions local field and action potentials using an inverter-based capacitively coupled low-noise amplifier, followed by a per-channel 10-b asynchronous SAR ADC. The adaptation of unit-length capacitors minimizes the ADC area and relaxes the amplifier gain so that small coupling capacitors can be integrated. The prototype in 65-nm CMOS achieves 4× smaller area and 3× higher energy–area efficiency compared to the state of the art with 164 μm×40μm footprint and 0.78 mm²× fJ/conv-step energy-area figure of merit. The measured 0.65- μW power consumption and 3.1 - μVrms input-referred noise within 1 Hz–10 kHz bandwidth correspond to a noise efficiency factor of 0.97

Design of a Configurable 4-Channel Analog Front-End for EEG Signal Acquisition on 180nm CMOS Process

In this work, a 4-channel Analog Front-End (AFE) circuit has been proposed for EEG signal recording. For EEG recording systems, the AFE may handle a wide range of sensor inputs with high input impedance, adjustable gain, low noise, and wide bandwidth. The buffer or current-to-voltage converter block (BCV), which can be set to operate as a buffer or a current-to-voltage converter circuit, is positioned between the electrode and the main amplifier stages of the AFE to achieve high input impedance and work with sensor signal types. A chopper capacitively-coupled instrumentation amplifier (CCIA) is positioned after the BCV as the main amplifier stage of the AFE to reduce input-referred noise and balance the impedance of the overall AFE system. A programmable gain amplifier (PGA) is the third stage of the AFE that allows the overall gain of the AFE to be adjusted. The suggested AFE operates in a wide frequency range of 0.5 Hz to 2 kHz with a high input impedance bigger than 2TΩ, and it is constructed and simulated using a 180nm CMOS process. With the lowest 100-dB CMRR and low input-referred noise of 1.8 µVrms, the AFE can achieve low noise efficiency. EEG signals can be acquired with this AFE system, which is very useful for detecting epilepsy and seizures

Bioelectronic Sensor Nodes for Internet of Bodies

Energy-efficient sensing with Physically-secure communication for bio-sensors on, around and within the Human Body is a major area of research today for development of low-cost healthcare, enabling continuous monitoring and/or secure, perpetual operation. These devices, when used as a network of nodes form the Internet of Bodies (IoB), which poses certain challenges including stringent resource constraints (power/area/computation/memory), simultaneous sensing and communication, and security vulnerabilities as evidenced by the DHS and FDA advisories. One other major challenge is to find an efficient on-body energy harvesting method to support the sensing, communication, and security sub-modules. Due to the limitations in the harvested amount of energy, we require reduction of energy consumed per unit information, making the use of in-sensor analytics/processing imperative. In this paper, we review the challenges and opportunities in low-power sensing, processing and communication, with possible powering modalities for future bio-sensor nodes. Specifically, we analyze, compare and contrast (a) different sensing mechanisms such as voltage/current domain vs time-domain, (b) low-power, secure communication modalities including wireless techniques and human-body communication, and (c) different powering techniques for both wearable devices and implants.Comment: 30 pages, 5 Figures. This is a pre-print version of the article which has been accepted for Publication in Volume 25 of the Annual Review of Biomedical Engineering (2023). Only Personal Use is Permitte

A 20 Mbps, 433 MHz RF ASK Transmitter to Inductively Power a Distributed Network of Miniaturised Neural Implants

Simultaneous wireless information and power transfer is an emerging technique in neurotechnology. This work presents an efficient transmitter for both power transfer and downlink data communication to multiple, miniaturised and inductively-powered chips. We designed, implemented and tested a radio-frequency transmitter operating at 433.92 MHz of the industrial, scientific and medical band. A new structure is proposed to efficiently modulate the carrier, exploiting an amplitude-shift keying modulation reaching a data rate as high as 20 Mbps together with a variable modulation index as low as 8%