Ultra-low power mixed-signal frontend for wearable EEGs

Electronics circuits are ubiquitous in daily life, aided by advancements in the chip design industry, leading to miniaturised solutions for typical day to day problems. One of the critical healthcare areas helped by this advancement in technology is electroencephalography (EEG). EEG is a non-invasive method of tracking a person's brain waves, and a crucial tool in several healthcare contexts, including epilepsy and sleep disorders. Current ambulatory EEG systems still suffer from limitations that affect their usability. Furthermore, many patients admitted to emergency departments (ED) for a neurological disorder like altered mental status or seizures, would remain undiagnosed hours to days after admission, which leads to an elevated rate of death compared to other conditions. Conducting a thorough EEG monitoring in early-stage could prevent further damage to the brain and avoid high mortality. But lack of portability and ease of access results in a long wait time for the prescribed patients. All real signals are analogue in nature, including brainwaves sensed by EEG systems. For converting the EEG signal into digital for further processing, a truly wearable EEG has to have an analogue mixed-signal front-end (AFE). This research aims to define the specifications for building a custom AFE for the EEG recording and use that to review the suitability of the architectures available in the literature. Another critical task is to provide new architectures that can meet the developed specifications for EEG monitoring and can be used in epilepsy diagnosis, sleep monitoring, drowsiness detection and depression study. The thesis starts with a preview on EEG technology and available methods of brainwaves recording. It further expands to design requirements for the AFE, with a discussion about critical issues that need resolving. Three new continuous-time capacitive feedback chopped amplifier designs are proposed. A novel calibration loop for setting the accurate value for a pseudo-resistor, which is a crucial block in the proposed topology, is also discussed. This pseudoresistor calibration loop achieved the resistor variation of under 8.25%. The thesis also presents a new design of a curvature corrected bandgap, as well as a novel DDA based fourth-order Sallen-Key filter. A modified sensor frontend architecture is then proposed, along with a detailed analysis of its implementation. Measurement results of the AFE are finally presented. The AFE consumed a total power of 3.2A (including ADC, amplifier, filter, and current generation circuitry) with the overall integrated input-referred noise of 0.87V-rms in the frequency band of 0.5-50Hz. Measurement results confirmed that only the proposed AFE achieved all defined specifications for the wearable EEG system with the smallest power consumption than state-of-art architectures that meet few but not all specifications. The AFE also achieved a CMRR of 131.62dB, which is higher than any studied architectures.Open Acces

Low Power, High PSR CMOS Voltage References

With integration of various functional modules such as radio frequency (RF) circuits, power management, and high frequency digital and analog circuits into one system on chip (SoC) in recent applications, power supply noise can cause significant system performance deterioration. This makes supply noise rejection of the embedded voltage reference crucial in modern SoC applications. Also the use of resistors in bandgap voltage references makes them less suitable for modern low power and portable applications. This thesis introduces two resistorless sub-1 V, all MOSFET references. The goal is to achieve a high power supply rejection (PSR) over a wide bandwidth not achieved in previous works. This high PSR over wide bandwidth is achieved by using a combination of a feedback technique and an innovative compact MOSFET low pass filter. The two references were fabricated in a standard 0.18 µm CMOS process. The first reference uses a composite transistor in subthreshold to produce a proportional-to-absolute temperature (PTAT) voltage which is converted to a current used to thermally compensate the threshold voltage of a MOSFET in saturation. The second references uses dynamic-threshold voltage MOSFET (DTMOS) to produce a PTAT voltage which is converted to a current used to thermally compensate the threshold voltage of a MOSFET in saturation. The measurement shows that both references consumes a sub-1 µW power across their entire operating temperatures. The first reference achieves a PSR better than 50 dB for frequencies of up to 70 MHz and a 20 ppm/°C temperature coefficient (TC) for temperatures from -35 °C — 80 °C. It has a compact area of 0.0180 mm2 and operates on a supply of 1.2 V — 2.3 V. The second reference achieves a PSR better than 50 dB for frequencies of up to 60 MHz. This reference achieves a TC of 9.33 ppm/°C after trimming for temperatures from -30 °C — 110 °C and a line regulation of 0.076 %/V for a step from 0.8 V to 2 V supply voltage with 360 nW power consumption at room temperature. It has a compact area of 0.0143 mm^2

Interface Circuits for Microsensor Integrated Systems

ca. 200 words; this text will present the book in all promotional forms (e.g. flyers). Please describe the book in straightforward and consumer-friendly terms. [Recent advances in sensing technologies, especially those for Microsensor Integrated Systems, have led to several new commercial applications. Among these, low voltage and low power circuit architectures have gained growing attention, being suitable for portable long battery life devices. The aim is to improve the performances of actual interface circuits and systems, both in terms of voltage mode and current mode, in order to overcome the potential problems due to technology scaling and different technology integrations. Related problems, especially those concerning parasitics, lead to a severe interface design attention, especially concerning the analog front-end and novel and smart architecture must be explored and tested, both at simulation and prototype level. Moreover, the growing demand for autonomous systems gets even harder the interface design due to the need of energy-aware cost-effective circuit interfaces integrating, where possible, energy harvesting solutions. The objective of this Special Issue is to explore the potential solutions to overcome actual limitations in sensor interface circuits and systems, especially those for low voltage and low power Microsensor Integrated Systems. The present Special Issue aims to present and highlight the advances and the latest novel and emergent results on this topic, showing best practices, implementations and applications. The Guest Editors invite to submit original research contributions dealing with sensor interfacing related to this specific topic. Additionally, application oriented and review papers are encouraged.

Solid State Circuits Technologies

The evolution of solid-state circuit technology has a long history within a relatively short period of time. This technology has lead to the modern information society that connects us and tools, a large market, and many types of products and applications. The solid-state circuit technology continuously evolves via breakthroughs and improvements every year. This book is devoted to review and present novel approaches for some of the main issues involved in this exciting and vigorous technology. The book is composed of 22 chapters, written by authors coming from 30 different institutions located in 12 different countries throughout the Americas, Asia and Europe. Thus, reflecting the wide international contribution to the book. The broad range of subjects presented in the book offers a general overview of the main issues in modern solid-state circuit technology. Furthermore, the book offers an in depth analysis on specific subjects for specialists. We believe the book is of great scientific and educational value for many readers. I am profoundly indebted to the support provided by all of those involved in the work. First and foremost I would like to acknowledge and thank the authors who worked hard and generously agreed to share their results and knowledge. Second I would like to express my gratitude to the Intech team that invited me to edit the book and give me their full support and a fruitful experience while working together to combine this book

Nickel oxide thin films grown by chemical deposition techniques: Potential and challenges in next‐generation rigid and flexible device applications

Funder: Aziz FoundationFunder: Downing College, CambridgeFunder: Isaac Newton Trust; Id: http://dx.doi.org/10.13039/501100004815Abstract: Nickel oxide (NiO x ), a p‐type oxide semiconductor, has gained significant attention due to its versatile and tunable properties. It has become one of the critical materials in wide range of electronics applications, including resistive switching random access memory devices and highly sensitive and selective sensor applications. In addition, the wide band gap and high work function, coupled with the low electron affinity, have made NiO x widely used in emerging optoelectronics and p‐n heterojunctions. The properties of NiO x thin films depend strongly on the deposition method and conditions. Efficient implementation of NiO x in next‐generation devices will require controllable growth and processing methods that can tailor the morphological and electronic properties of the material, but which are also compatible with flexible substrates. In this review, we link together the fundamental properties of NiO x with the chemical processing methods that have been developed to grow the material as thin films, and with its application in electronic devices. We focus solely on thin films, rather than NiO x incorporated with one‐dimensional or two‐dimensional materials. This review starts by discussing how the p‐type nature of NiO x arises and how its stoichiometry affects its electronic and magnetic properties. We discuss the chemical deposition techniques for growing NiO x thin films, including chemical vapor deposition, atomic layer deposition, and a selection of solution processing approaches, and present examples of recent progress made in the implementation of NiO x thin films in devices, both on rigid and flexible substrates. Furthermore, we discuss the remaining challenges and limitations in the deposition of device‐quality NiO x thin films with chemical growth methods. imag

Thin‐Film Transistors for Large Area Opto/Electronics

The present work addresses several issues in the field of organic and transparent electronics. One of them is the prevailing high power consumption in state-of-the-art organic field-effect transistors (OFETs). A possible solution could be the implementation of complementary, rather than unipolar logic, but this development is currently inhibited by a distinct lack of high performance electron transporting (n-channel) OFETs. Here, the issue is addressed by investigating a series of solution processable n-channel fullerene molecules in combination with optimized transistor architectures. Furthermore, the trend towards complementary circuit design could be facilitated by employing ambipolar organic semiconductors, such as squaraine molecules or polymer/fullerene blends. These materials can fill the role of p- or n-channel semiconductors and enable the facile implementation of power saving complementary-like logic, eliminating the cost-intensive patterned deposition of discrete p-and n-channel transistors. Alternatively, a patterning method for organic materials adapted from standard photolithography is discussed. Furthermore, ambipolar FETs are found to be capable of light sensing at wavelength of 400-1000 nm. Hence their use in low-cost, organic based optical sensor arrays can be envisioned. Another strategy to reduce the power consumption and operating voltages of OFETs is the use of ultra-thin, self-assembled molecular gate dielectrics, such as alkyl-phosphonic acid molecules. Based on this approach solution processed n- and p-channel OFETs and a complementary organic inverter circuit are demonstrated, which operate at less than 2 Volts. Finally, transparent oxide semiconductors are investigated for use in thin-film transistors. Titanium dioxide (TiO2) and zinc oxide (ZnO) films are deposited by means of a low-cost large area compatible spray pyrolysis technique. ZnO transistors exhibit high electron mobility of the order of 10 cm2/Vs and stable operation in air at less than 2 Volts. These results are considered significant steps towards the development of organic and transparent large-area optoelectronics

Silicon Nanodevices

This book is a collection of scientific articles which brings research in Si nanodevices, device processing, and materials. The content is oriented to optoelectronics with a core in electronics and photonics. The issue of current technology developments in the nanodevices towards 3D integration and an emerging of the electronics and photonics as an ultimate goal in nanotechnology in the future is presented. The book contains a few review articles to update the knowledge in Si-based devices and followed by processing of advanced nano-scale transistors. Furthermore, material growth and manufacturing of several types of devices are presented. The subjects are carefully chosen to critically cover the scientific issues for scientists and doctoral students

Disseny microelectrnic de circuits discriminadors de polsos pel detector LHCb

The aim of this thesis is to present a solution for implementing the front end system of the Scintillator Pad Detector (SPD) of the calorimeter system of the LHCb experiment that will start in 2008 at the Large Hadron Collider (LHC) at CERN. The requirements of this specific system are discussed and an integrated solution is presented, both at system and circuit level. We also report some methodological achievements. In first place, a method to study the PSRR (and any transfer function) in fully differential circuits taking into account the effect of parameter mismatch is proposed. Concerning noise analysis, a method to study time variant circuits in the frequency domain is presented and justified. This would open the possibility to study the effect of 1/f noise in time variants circuits. In addition, it will be shown that the architecture developed for this system is a general solution for front ends in high luminosity experiments that must be operated with no dead time and must be robust against ballistic deficit

Wide Bandgap Based Devices: Design, Fabrication and Applications, Volume II

Wide bandgap (WBG) semiconductors are becoming a key enabling technology for several strategic fields, including power electronics, illumination, and sensors. This reprint collects the 23 papers covering the full spectrum of the above applications and providing contributions from the on-going research at different levels, from materials to devices and from circuits to systems