Reliable Circuit Techniques for Low-Voltage Analog Design in Deep Submicron Standard CMOS: A Tutorial

We present in this paper an overview of circuit techniques dedicated to design reliable low-voltage (1-V and below) analog functions in deep submicron standard CMOS processes. The challenges of designing such low-voltage and reliable analog building blocks are addressed both at circuit and physical layout levels. State-of-the-art circuit topologies and techniques (input level shifting, bulk and current driven, DTMOS), used to build main analog modules (operational amplifier, analog CMOS switches) are covered with the implementation of MOS capacitors.     

Thermal stability and crosslinking of hydropolysilanes for use as silicon carbide precursors

Thermal stability of [(CH₃SiH)₃₀(C₆H₅SiCH₃)₇₀]_n a hydropolysilane copolymer, in vacuum and its crosslinking reactions with vinylic silanes as crosslinking agents was evaluated in order to obtain high yields of oxygen-free silicon carbide ceramics. It was found that the polymer was thermally stable in vacuum up to 140 °C for 20 hrs based on Fourier transform infrared spectroscopy analysis. The crosslinking reactions of the polymer occurred to various extents depending on the type of vinylic silanes used as evidenced by Fourier transform infrared spectroscopy, ultraviolet spectroscopy, gel permeation chromatography, thermogravimetry and solubility data. The additions of vinylic silanes to Si-H in the hydropolysilane were found to obey anti-Farmer's rule, despite Farmer's addition of unsaturated hydrocarbons to Si-H.     

Charge-Based Capacitive Sensor Array for CMOS-Based Laboratory-on-Chip Applications

In this paper, we present a capacitive sensor array for highly integrated lab-on-chip (LoC) applications using the charge-based capacitance measurement method (CBCM). The core-CBCM sensor chip is designed and implemented in 0.18 micron CMOS process featuring an array of capacitive sensors; an offset cancellation module and a low complexity analog-to-digital converter (ADC). This sensor chip is incorporated with a microfluidic channel using direct-write fabrication process. We demonstrate the testing results using chemical solvents with known dielectric constants in order to show the viability of the proposed sensor chip for LoCs.     

A high‐voltage stimulation chip for wearable stroke rehabilitation systems

In this work, an 8‐channel high‐voltage (HV) stimulation chip for the rehabilitation of stroke patients through surface stimulation is presented. The chip receives control data through its serial peripheral interface and can be controlled by an external microcontroller. It can accordingly generate biphasic stimulation currents with different amplitudes, duration time, frequencies, and polarities for each channel independently. The chip was designed and fabricated using X‐FAB 0.35 µm HV mixed‐signal process. Circuits were carefully designed to ensure their operations under HVs. Our measurement results showed that a supply voltage of as high as 75 V can be achieved, and the current driver can generate biphasic stimuli with current amplitudes up to 4 mA. Copyright © 2015 John Wiley & Sons, Ltd.     

Optimizing the power-sensitivity trade-off in TRF receivers

There is an inevitable trade-off between the sensitivity of an RF receiver and its total power consumption, meaning that in order to design a receiver with a high sensitivity, more power must be dissipated. Ultra-low power receivers in general and wake-up receivers in particular require a sensitivity of better than ?70 dBm while the power consumption should be as low as possible at the same time. Therefore, obtaining an optimum point where these two design specifications are met is of great interest. In this work, we present a design methodology for the tuned radio frequency (TRF) receiver topology, which yields an optimum power-sensitivity product for given design parameters. The most interesting outcome of this study is finding an optimum number of amplifier stages at the front-end of the receiver that leads to a minimum power-sensitivity product. It is shown through analytical/graphical approach in Matlab that the optimum number of stages resulting in the minimum power-sensitivity product can be different from the optimum number of amplifier stages leading to the maximum overall gain-bandwidth product. These results are also verified through circuit-level simulation with Cadence Spectre for practical design parameters. According to our study, the minimum power-sensitivity product occurs for a two-stage amplifier with moderate gain at the front-end of the TRF receiver.     

Interaction of supercritical carbon dioxide with polymers. I. Crystalline polymers

Supercritical fluid (SCF) technology involving carbon dioxide is recently receiving wide attention due to its vast potential application in various fields such as cleaning, extraction, synthesis, etc., in addition to its environmental benefits. To fully exploit the use of SCFs in new technologies, it is important to understand how SCFs interact with materials. To this end, we have undertaken a systematic study involving a wide pressure and temperature range to investigate the interaction of supercritical carbon dioxide (SC CO₂) with nine different crystalline polymers, namely, substituted and unsubstituted polyethylene (four varieties), polypropylene, nylon 66, poly(ethylene terephthalate), poly(oxymethylene), and poly(vinylidine fluoride). Critical factors such as changes in appearance and weight, temperature, pressure and time of the supercritical fluid treatment, and dimension of samples have been observed. The influence of SC CO₂ on the thermal properties of treated polymers has been investigated through TGA analysis. Further, changes in the mechanical properties such as yield strength, ultimate elongation, and modulus of elasticity of the investigated crystalline polymers were also observed. A discussion has been included to show the possible implications of the observed changes in realizing various applications. © 1996 John Wiley & Sons, Inc.     

A 1.8 V CMOS fourth-order Gm-C bandpass sigma-delta modulator dedicated to front-end ultrasonic receivers

A 4th order bandpass sigma-delta modulator for ultrasound applications is presented. By cascading two second-order identical Gm-C bandpass filters, a 4th-order modulator was designed with high power-efficiency, stability, tunability and programmability. The modulator is dedicated for application with intermediate frequency of 3 MHz and bandwidth of 200 kHz. Implemented in a standard 0.18 μm CMOS technology, the post-layout simulation of the modulator gives a dynamic range of 78 dB. Chip measurements are reported after successfully tuning the modulator to operate at four-time of its folded specifications. The final SNR achieves 58 dB at 0.75 MHz with 50 kHz bandwidth. The modulator consumes 2.5 mW from 1.8 V power supply. Moreover, a programming method is introduced and corresponding circuit is designed to change the central frequency of the modulator between 3 and 20 MHz for scanning different regions of the body. However the 200 kHz bandwidth limits the modulator only for Dobbler mode applications, the effective facilities of programmability are valuable property to expand this application to other wide band applications in future. Lisheng Qin received the B.Sc. degree in electrical engineering from Tianjin University, China in 1992. He was with Polystim Neurotechnologies Laboratory from 2001 to 2005 and received the M.Sc. degree in electronics engineering from Ecole Polytechnique de Montreal, Canada in 2005. He is now with Apexone Microelectronics Inc. as Analog/Mixed-Signal Design Engineer. Kamal El-Sankary received the B.Sc. degree in electrical engineering from the Lebanese University, Lebanon in 1997 and the M.Sc. degree in electronics engineering from University of Quebec in Trois Rivieres, Canada, in 2001. He is currently pursuing the Ph.D. degree in microelectronics at Ecole Polytechnique de Montreal, Canada. His research interests include analog/mixed-signal circuits design and signal processing. Mohamad Sawan received the B.Sc. degree in electrical engineering from Université Laval, Canada in 1984, the M.Sc. and Ph.D. degrees, both in electrical engineering, from Université de Sherbrooke, Canada, in 1986 and 1990 respectively, and postdoctorate training from McGill University, Canada in 1991. He joined Ecole Polytechnique de Montréal in 1991 where he is currently a Professor in Microelectronics. His scientific interests are the design and test of mixed-signal (analog, digital and RF) circuits and systems, the digital and analog signal processing, the modeling, design, integration, assembly and validation of advanced wirelessly powered and controlled monitoring and measurement techniques. These topics are oriented toward the biomedical implantable devices and telecommunications applications. Dr. Sawan is a holder of a Canadian Research Chair in Smart Medical Devices. He is leading the Microelectronics Strategic Alliance of Quebec (Regroupement stratégique en microélectronique du Québec - ReSMiQ). He is founder of the Eastern Canadian IEEE-Solid State Circuits Society Chapter, the International IEEE-NEWCAS conference, and Polystim neurotechnologies laboratory at the Ecole Polytechnique de Montreal. He is cofounder of the International Functional Electrical Stimulation Society (IFESS), and the IEEE International conference on Electronics, Circuits and Systems (ICECS). Dr. Sawan is involved in the committees of many national and international conferences and other scientific events. He published more than 300 papers in peer reviewed journals and conference proceedings and is awarded 6 patents. He is editor of the Springer Mixed-signal Letters, Distinguished Lecturer for the IEEE CAS Society, President of the biomedical circuits and systems (BioCAS) technical committee of the IEEE CAS Society, and he is representative of IEEE-CAS in the International Biotechnology council. He received the Barbara Turnbull 2003 award for spinal cord research, the Medal of Merit from Lebanon, and the Bombardier Medal from the French Association for the advancement of sciences. Dr. Sawan is Fellow of the Canadian Academy of Engineering, and Fellow of the IEEE.