An Improved Wideband CMOS Current Driver for Bioimpedance Applications

A wideband, CMOS current driver for bioimpedance measurement applications has been designed employing nonlinear feedback. With the introduction of phase compensation, the circuit is able to operate at frequencies higher than the pole frequency of the output transconductor with minimum phase delay. Moreover, it isolates the poles required for stability from the high frequency characteristics of the output transconductor. The circuit has been simulated in a 0.35-μm CMOS technology and operates from ±2.5 V power supplies. Simulations show that for a 1 mAp-p output current, the phase delay is less than 1° for frequencies up to 3 MHz, rising to 1.5° at 5 MHz. Dual frequency currents to the load are demonstrated

On the application of frequency selective common mode feedback for multifrequency EIT

Common mode voltages are frequently a problem in electrical impedance tomography (EIT) and other bioimpedance applications. To reduce their amplitude common mode feedback is employed. Formalised analyses of both current and voltage feedback is presented in this paper for current drives. Common mode effects due to imbalances caused by the current drives, the electrode connections to the body load and the introduction of the body impedance to ground are considered. Frequency selective narrowband common mode feedback previously proposed to provide feedback stability is examined. As a step towards multifrequency applications the use of narrowband feedback is experimentally demonstrated for two simultaneous current drives. Measured results using standard available components show a reduction of 62dB for current feedback and 31dB for voltage feedback. Frequencies ranged from 50 kHz to 1 MHz

A CMOS Magnitude/Phase Measurement Chip for Impedance Spectroscopy

The measurement of electrical impedance is used in a plethora of biomedical applications. The most common technique used is synchronous demodulation, which provides the real and imaginary parts of the impedance. However, in practice, the method requires elaborate calibration and matching between the injection and monitoring stages. This paper presents the integrated realization of an alternative method that is less intricate to implement. The circuit was fabricated in a 0.35-μm CMOS technology, occupies an active area of 0.4 mm2 , and dissipates about 21 mW of power from ±2.5 V supplies. The chip was used to measure equivalent RC circuits of the electrode-tissue interface over the frequency range of 100 Hz to 100 kHz, showing good correlation with the theoretical results

Design of a CMOS active electrode IC for wearable electrical impedance tomography systems

This paper describes the design of an active electrode integrated circuit (IC) for a wearable electrical impedance tomography (EIT) system required for real time monitoring of neonatal lung function. The IC comprises a wideband high power current driver (up to 6 mAp-p output current), a low noise voltage amplifier and two shape sensor buffers. The IC has been designed in a 0.35-μm CMOS technology. It operates from ±9 V power supplies and occupies a total die area of 5 mm2. Post-layout simulations are presented

An Integrated Analog Readout for Multi-Frequency Bioimpedance Measurements

Bioimpedance spectroscopy is used in a wide range of biomedical applications. This paper presents an integrated analog readout, which employs synchronous detection to perform galvanostatic multi-channel, multi-frequency bioimpedance measurements. The circuit was fabricated in a 0.35-μm CMOS technology and occupies an area of 1.52 mm2. The effect of random dc offsets is investigated, along with the use of chopping to minimize them. Impedance measurements of a known RC load and skin (using commercially available electrodes) demonstrate the operation of the system over a frequency range up to 1 MHz. The circuit operates from a ±2.5 V power supply and has a power consumption of 3.4-mW per channel

Efficient Dual Output Regulating Rectifier and Adiabatic Charge Pump for Biomedical Applications Employing Wireless Power Transfer †

A power management unit (PMU) is an essential block for diversified multi-functional low-power Internet of Things (IoT) and biomedical electronics. This paper includes a theoretical analysis of a high current, single-stage ac-dc, reconfigurable, dual output, regulating rectifier consisting of pulse width modulation (PWM) and pulse frequency modulation (PFM). The regulating rectifier provides two independently regulated supply voltages of 1.8 V and 3.3 V from an input ac voltage. The PFM control feedback consists of feedback-driven regulation to adjust the driving frequency of the power transistors through adaptive buffers in the active rectifier. The PWM/PFM mode control provides a feedback loop to adjust the conduction duration accurately and minimize power losses. The design also includes an adiabatic charge pump (CP) to provide a higher voltage level. The adiabatic CP consists of latch-up and power-saving topologies to enhance its power efficiency. Simulation results show that the dual regulating rectifier has 94.3% voltage conversion efficiency with an ac input magnitude of 3.5 Vp. The power conversion efficiency of the regulated 3.3 V output voltage is 82.3%. The adiabatic CP has an overall voltage conversion efficiency (VCE) of 92.9% with a total on-chip capacitance of 60 pF. The circuit was designed using 180 nm CMOS technology

Cognitive Function in Patients Undergoing Arthroplasty: The Implications for Informed Consent

Obtaining informed consent for an operation is a fundamental daily interaction between orthopaedic surgeon and patient. It is based on a patient's capacity to understand and retain information about the proposed procedure, the potential consequences of having it, and the alternative options available. We used validated tests of memory on 59 patients undergoing lower limb arthroplasty to assess how well they learned and recalled information about their planned procedure. All patients showed an ability to learn new material; however, younger age and higher educational achievement correlated with better performance. These results have serious implications for orthopaedic surgeons discussing planned procedures. They identify groups of patients who may require enhanced methods of communicating the objectives, risks, and alternatives to surgery. Further research is necessary to assess interventions to improve communication prior to surgery

A CMOS current driver with built-in common-mode signal reduction capability for EIT

This paper presents an integrated fully differential current driver for wearable multi-frequency electrical impedance tomography (EIT). The integrated circuit (IC) comprises a wideband current driver (up to 500 kHz) functioning as the master for current sourcing, and a differential voltage receiver with common-mode feedback configuration as the slave for current sinking. The IC is fabricated in a 0.18-µm CMOS technology. It operates from ±1.65 V power supplies and occupies a total die area of less than 0.05 mm2 . The current driver has a measured output impedance of 750 kΩ at 500 kHz and provides a common-mode signal reduction of 32 dB at 500 kHz. The application of the IC in a wearable EIT lung monitoring system is presented

A Non-Linear Feedback Current Driver With Automatic Phase Compensation for Bioimpedance Applications

In a conventional sinewave current driver for electrical impedance spectroscopy, as the frequency is increased the input/output phase delay of the current driver increases due to limited bandwidth. The required maximum phase delays of < 4o mean that operation is limited to about 1/12 of the driver bandwidth. A new phase compensation scheme is presented to reduce the phase delay at higher frequencies and can extend the useful operating frequency range of a current driver. The system is capable of reducing the phase error due to the current driver by an appreciable level so that it can operate much nearer the pole frequency of the driver. An integrated circuit was fabricated in a 0.35 5m CMOS process technology which provides a phase error reduction from 22o to 3o at 3 MHz. Its core occupies a silicon area of 1.2 mm2. It operates from a ±2.5 V power supply and can deliver output currents up to 1.8 mAp-p at 3 MHz

Deregulation of Polycomb Repressive Complex-2 in Mantle Cell Lymphoma Confers Growth Advantage by Epigenetic Suppression of

The polycomb repressive complex 2 (PRC2) maintains the transcriptional repression of target genes through its catalytic component enhancer of zeste homolog 2 (EZH2). Through modulating critical gene expression, EZH2 also plays a role in cancer development and progression by promoting cancer cell survival and invasion. Mutations in EZH2 are prevalent in certain B-cell lymphoma subtypes such as diffuse large cell lymphoma and follicular lymphoma; while no EZH2 mutation has been reported in the mantle cell lymphoma (MCL). Here we demonstrate that the PRC2 components EZH2, EED and SUZ12 are upregulated in the MCL cells as compared to normal B-cells. Moreover, stably transfected cells with wild-type EZH2 or-EED showed increased cell growth and H3K27-trimehtylation. However, unlike wild-type EZH2, ectopic expression of a deletion construct of EZH2 (EZH