New data services and applications are emerging continuously and enhancing the mobile broadband experience. The ability to cope with these varied and sophisticated services and applications will be a key success factor for the highly demanding future network infrastructure. One such technology that could help address the problem would be optical wireless communications (OWC), which presents a growing research interest in the last few years for indoor and outdoor applications. This paper is an overview of the OWC systems focusing on visible light communications, free space optics, transcutaneous OWC, underwater OWC, and optical scattering communications.

Emerging Optical Wireless Communications-Advances and Challenges

During recent years, silicon carbide (SiC) power electronics has gone from being a promising future technology to being a potent alternative to state-of-the-art silicon (Si) technology in high-efficiency, highfrequency, and high-temperature applications. The reasons for this are that SiC power electronics may have higher voltage ratings, lower voltage drops, higher maximum temperatures, and higher thermal conductivities. It is now a fact that several manufacturers are capable of developing and processing high-quality transistors at cost that permit introduction of new products in application areas where the benefits of the SiC technology can provide significant system advantages.

Silicon Carbide Power Transistors: A New Era in Power Electronics Is Initiated

This paper presents a 60-dB gain bulk-driven Miller OTA operating at 0.25-V power supply in the 130-nm digital CMOS process. The amplifier operates in the weak-inversion region with input bulk-driven differential pair sporting positive feedback source degeneration for transconductance enhancement. In addition, the distributed layout configuration is used for all the transistors to mitigate the effect of halo implants for higher output impedance. Combining these two approaches, we experimentally demonstrate a high gain of over 60-dB with just 18-nW power consumption from 0.25-V power supply. The use of enhanced bulk-driven differential pair and distributed layout can help overcome some of the constraints imposed by nanometer CMOS process for high performance analog circuits in weak inversion region.

A 60-dB Gain OTA Operating at 0.25-V Power Supply in 130-nm Digital CMOS Process

A high-temperature dielectric, (1–x)(0.6Bi1/2Na1/2TiO3–0.4Bi1/2K1/2TiO3)–xK0.5Na0.5NbO3, off the morphotropic phase boundary of the parent matrix 0.8Bi1/2Na1/2TiO3–0.2Bi1/2K1/2TiO3, has been developed for application as a high-temperature capacitor. In addition to temperature-dependent permittivity and dielectric loss, DC conductivity and field-dependent permittivity are reported. These properties are correlated with temperature-dependent structure data measured at different length scales using Raman spectroscopy and neutron diffraction. It is suggested that all materials investigated are ergodic relaxors with two types of polar nanoregions providing different relaxation mechanisms. The most attractive properties for application as high-temperature dielectrics are obtained in a material with x = 0.15 at less than 10% variation of relative permittivity of about 2100 between 54°C and 400°C.

A High-Temperature-Capacitor Dielectric Based on K0.5Na0.5NbO3-Modified Bi1/2Na1/2TiO3–Bi1/2K1/2TiO3

A simple high-performance architecture for bulk-driven operational transconductance amplifiers (OTAs) is presented. The solution, suitable for operation under sub 1-V single supply, is made up of three gain stages and, as an additional feature, provides inherent class-AB behavior with accurate and robust standby current control. The OTA is fabricated in a 180-nm standard CMOS technology, occupies an area of $19.8\cdot 10^{-3}\ \text{mm}^{2}$ and is powered from 0.7 V with a standby current consumption of around 36 $\mu\text{A}$ . DC gain and unity gain frequency are 57 dB and 3 MHz, respectively, under a capacitive load of 20 pF. Overall good large-signal and small-signal performances are achieved, making the solution extremely competitive in comparison to the state of the art.

0.7-V Three-Stage Class-AB CMOS Operational Transconductance Amplifier

This paper presents two low-voltage bulk-driven amplifier input stages with enhanced transconductance. The idea is to introduce auxiliary differential pairs into a conventional bulk-driven stage to boost its transconductance. A low-voltage cascode biasing circuitry based on EKV models is also employed to ensure proper operation of the proposed input stages. An operational amplifier is then implemented with the proposed input stages and biasing circuits as its core building blocks and including a modified low-voltage class AB output amplifier to guarantee rail-to-rail output voltage range. The overall amplifier was implemented in a 0.35 μm n-well CMOS process using 1-V power supply. The measurement results show significant improvement in the performance of the operational amplifier compared to prior arts.

Low-Voltage Bulk-Driven Operational Amplifier With Improved Transconductance

The growing demand for hybrid electric vehicles (HEVs) has increased the need for high-temperature electronics that can operate at the extreme temperatures that exist under the hood. This paper presents a high-voltage, high-temperature SOI-based gate driver for SiC FET switches. The gate driver is designed and implemented on a 0.8-micron BCD on SOI process. This gate driver chip is intended to drive SiC power FETs for DC-DC converters and traction drives in HEVs. To this end, the gate driver IC has been successfully tested up to 200oC. Successful operation of the circuit at this temperature with minimal or no heat sink, and without liquid cooling, will help to achieve higher power-to-volume as well as power-to-weight ratios for the power electronics modules in HEVs.

SOI-based integrated circuits for high-temperature power electronics applications

Implantable sensors for continuous glucose monitoring hold great potential for optimal diabetes management. This is often undermined by a variety of issues associated with: (1) negative tissue response; (2) poor sensor performance; and (3) lack of device miniaturization needed to reduce implantation trauma. Herein, we report our initial results towards constructing an implantable device that simultaneously address all three aforementioned issues. In terms of device miniaturization, a highly miniaturized CMOS (complementary metal-oxide-semiconductor) potentiostat and signal processing unit was employed (with a combined area of 0.665 mm2). The signal processing unit converts the current generated by a transcutaneous, Clark-type amperometric sensor to output frequency in a linear fashion. The Clark-type amperometric sensor employs stratification of five functional layers to attain a well-balanced mass transfer which in turn yields a linear sensor response from 0 to 25 mM of glucose concentration, well beyond the physiologically observed (2 to 22 mM) range. In addition, it is coated with a thick polyvinyl alcohol (PVA) hydrogel with embedded poly(lactic-co-glycolic acid) (PLGA) microspheres intended to provide continuous, localized delivery of dexamethasone to suppress inflammation and fibrosis. In vivo evaluation in rat model has shown that the transcutaneous sensor system reproducibly tracks repeated glycemic events. Clarke’s error grid analysis on the as—obtained glycemic data has indicated that all of the measured glucose readings fell in the desired Zones A & B and none fell in the erroneous Zones C, D and E. Such reproducible operation of the transcutaneous sensor system, together with low power (140 μW) consumption and capability for current-to-frequency conversion renders this a versatile platform for continuous glucose monitoring and other biomedical sensing devices.

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A miniaturized transcutaneous system for continuous glucose monitoring

In this brief, a 1-V potentiostat circuit for a glucose sensor has been proposed. Test results of this 1-V potentiostat demonstrate high linearity with respect to glucose concentration, which is comparable with conventional potentiostat designs. This high linearity is achieved with the help of a transconductance enhanced bulk-driven operational amplifier. The overall current consumption of the circuit is around 22 μA. The potentiostat is tested as a glucose biosensor for glucose concentration ranging from 0 to 30 mM. The design is realized in a 0.35-μm bulk-CMOS process, and the area for the core layout is 0.13 mm2. The proposed low-power potentiostat can be incorporated in an implantable glucose sensor system due to its low-power operation and small footprint.

A Low-Power 1-V Potentiostat for Glucose Sensors

An implantable bio-sensing platform architecture that enables the wireless selection, calibration and reading of multiple sensors, as well as checking the power levels of the solar powering source energizing various electronic and optoelectronic devices and circuits embedded in the platform. It also permits checking the operation of the potentiostats interfacing with each amperometric analyte sensor. The platform is flexible to include FET based sensors for protein sensing as well as other applications including pH sensing. In addition, other physiological sensors can be integrated in the platform.

Liang Zuo

Papers

Low-Voltage Bulk-Driven Operational Amplifier With Improved Transconductance

SOI-based integrated circuits for high-temperature power electronics applications

A miniaturized transcutaneous system for continuous glucose monitoring

A Low-Power 1-V Potentiostat for Glucose Sensors

Circuit architecture and system for implantable multi-function and multi-analyte biosensing device