scholarly journals High Impedance Amplifiers for Non-Contact Bio-Potential Sensing

2021 ◽  
Author(s):  
◽  
Brett Ryan
Keyword(s):  
Positive Feedback ◽  
Input Impedance ◽  
Field Effect Transistors ◽  
Input Voltage ◽  
Settling Time ◽  
Voltage Noise ◽  
Noise Spectral Density ◽  
High Impedance ◽  
Transient Events ◽  
Mechanical Disturbances

<p>This research develops a non-contact bio-potential sensor which can quickly respond to input transient events, is insensitive to mechanical disturbances, and operates with a bandwidth from 0.04Hz – 20kHz, with input voltage noise spectral density of 200nV / √Hz at 1kHz.  Initial investigations focused on the development of an active biasing scheme to control the sensors input impedance in response to input transient events. This scheme was found to significantly reduce the settling time of the sensor; however the input impedance was degraded, and the device was sensitive to distance fluctuations. Further research was undertaken, and a circuit developed to preserve fast settling times, whilst decreasing the sensitivity to distance fluctuations.  A novel amplifier biasing network was developed using a pair of junction field effect transistors (JFETs), which actively compensates for DC and low frequency interference, whilst maintaining high impedance at signal frequencies. This biasing network significantly reduces the settling time, allowing bio-potentials to be measured quickly after sensor application, and speeding up recovery when the sensor is in saturation.  Further work focused on reducing the sensitivity to mechanical disturbances even further. A positive feedback path with low phase error was introduced to reduce the effective input capacitance of the sensor. Tuning of the positive feedback loop gain was achieved with coarse and fine control potentiometers, allowing very precise gains to be achieved. The sensor was found to be insensitive to distance fluctuations of up to 0.5mm at 1Hz, and up to 2mm at 5kHz.  As a complement to the non-contact sensor, an amplifier to measure differential bio-potentials was developed. This differential amplifier achieved a CMRR of greater than 100dB up to 10kHz. Precise fixed gains of 20±0:02dB, 40±0:01dB, 60±0:03dB, and 80±0:3dB were achieved, with input voltage noise density of 15nV / √Hz at 1kHz.</p>

scholarly journals High Impedance Amplifiers for Non-Contact Bio-Potential Sensing

2021 ◽  
Author(s):  
◽  
Brett Ryan
Keyword(s):  
Positive Feedback ◽  
Input Impedance ◽  
Field Effect Transistors ◽  
Input Voltage ◽  
Settling Time ◽  
Voltage Noise ◽  
Noise Spectral Density ◽  
High Impedance ◽  
Transient Events ◽  
Mechanical Disturbances

<p>This research develops a non-contact bio-potential sensor which can quickly respond to input transient events, is insensitive to mechanical disturbances, and operates with a bandwidth from 0.04Hz – 20kHz, with input voltage noise spectral density of 200nV / √Hz at 1kHz.  Initial investigations focused on the development of an active biasing scheme to control the sensors input impedance in response to input transient events. This scheme was found to significantly reduce the settling time of the sensor; however the input impedance was degraded, and the device was sensitive to distance fluctuations. Further research was undertaken, and a circuit developed to preserve fast settling times, whilst decreasing the sensitivity to distance fluctuations.  A novel amplifier biasing network was developed using a pair of junction field effect transistors (JFETs), which actively compensates for DC and low frequency interference, whilst maintaining high impedance at signal frequencies. This biasing network significantly reduces the settling time, allowing bio-potentials to be measured quickly after sensor application, and speeding up recovery when the sensor is in saturation.  Further work focused on reducing the sensitivity to mechanical disturbances even further. A positive feedback path with low phase error was introduced to reduce the effective input capacitance of the sensor. Tuning of the positive feedback loop gain was achieved with coarse and fine control potentiometers, allowing very precise gains to be achieved. The sensor was found to be insensitive to distance fluctuations of up to 0.5mm at 1Hz, and up to 2mm at 5kHz.  As a complement to the non-contact sensor, an amplifier to measure differential bio-potentials was developed. This differential amplifier achieved a CMRR of greater than 100dB up to 10kHz. Precise fixed gains of 20±0:02dB, 40±0:01dB, 60±0:03dB, and 80±0:3dB were achieved, with input voltage noise density of 15nV / √Hz at 1kHz.</p>

Inverter design with positive feedback field-effect transistors

2021 ◽  
Author(s):  
Changhoon Lee ◽  
Changwoo Han ◽  
Changhwan Shin
Keyword(s):  
Positive Feedback ◽  
Computer Aided Design ◽  
Field Effect ◽  
Field Effect Transistors ◽  
Feedback Mechanism ◽  
Silicon On Insulator ◽  
Logic Device ◽  
Device Applications ◽  
Positive Feedback Mechanism ◽  
Switching Devices

Abstract As the physical size of semiconductor devices continues to be aggressively scaled down, feedback field-effect transistors (FBFET) with a positive feedback mechanism among a few promising steep switching devices have received attention as next-generation switching devices. Conventional FBFETs have been studied to explore their device performance. However, this has been restricted to the case of single FBFET; basic circuit designs with FBFETs have not been investigated extensively. In this work, we propose an inverter circuit design with silicon-on-insulator (SOI) FBFETs; we verified this inverter design with mixed-mode technology computer-aided design simulation. The basic principles and mechanisms for designing FBFET inverter circuits are explained because their configuration is different from conventional inverters. In addition, the device parameters necessary to optimize circuit construction are introduced for logic device applications.

An Ultra-High Input Impedance Analog Front End Using Self-Calibrated Positive Feedback

2018 ◽  
Vol 53 (8) ◽  
pp. 2252-2262 ◽  
Author(s):  
Jinseok Lee ◽  
Geon-Hwi Lee ◽  
Hyojun Kim ◽  
SeongHwan Cho
Keyword(s):  
Positive Feedback ◽  
Input Impedance ◽  
High Input ◽  
High Input Impedance ◽  
Front End ◽  
Analog Front End

Thermal Characterization of Non-Isolated DC to DC Convertor

2011 ◽  
Author(s):  
Shiladitya Chakravorty ◽  
Bahgat Sammakia ◽  
Varaprasad Calmidi
Keyword(s):  
Power Dissipation ◽  
High Performance ◽  
Field Effect Transistors ◽  
Thermal Characteristics ◽  
Thermal Characterization ◽  
Input Voltage ◽  
Thermal Design ◽  
Power Module ◽  
Improved Performance

Improved performance of semiconductor devices in recent years has resulted in consequent increase in power dissipation. Hence thermal characterization of components becomes important from an overall thermal design perspective of the system. This study looks at a high performance non-isolated point of load power module (a DC to DC converter) meant for advanced computing and server applications. Thermal characteristics of the module were experimentally analyzed by placing the power module on a bare test board (with no insulation) inside a wind tunnel with thermocouples attached to it. There were three devices on this module that dissipate power. There were two FETs (Field Effect Transistors) and an inductor which can be considered as sources. The consolidated power dissipation from the module was calculated by measuring the input voltage and input current while keeping the output voltage and current constant. Temperatures at various points on the module and the test card were recorded for different air flow velocities and overall power dissipation. Subsequently this set up was numerically analyzed using a commercially available computational fluid dynamics (CFD) code with the objective of comparing the results with experimental data previously obtained.

scholarly journals Understanding of Feedback Field-Effect Transistor and Its Applications

2020 ◽  
Vol 10 (9) ◽  
pp. 3070 ◽  
Author(s):  
Changhoon Lee ◽  
Juho Sung ◽  
Changhwan Shin
Keyword(s):  
Power Consumption ◽  
Positive Feedback ◽  
Field Effect ◽  
Feedback Loop ◽  
Field Effect Transistors ◽  
Memory Device ◽  
Device Structure ◽  
Saturation Region ◽  
Effect Transistor ◽  
Channel Region

Feedback field-effect transistors (FBFETs) are devices based on a positive feedback loop in which the electrons and holes in the channel region act on the energy states of the potential barrier and wall. Owing to the positive feedback phenomenon, FBFETs have an excellent subthreshold swing (~0 mV/decade at 300 K), a high on-/off current ratio (~1010), and a clear saturation region. The power consumption of both the turn-on state and turn-off state is significantly low until operation commences. In addition, the hysteresis caused by the carriers accumulated in the potential wall allows the FBFET to act as a memory device. Moreover, the power consumption of neuromorphic devices can be suppressed by ~100 times with the use of FBFETs. In this work, we analyze the device structure and operating principle of the FBFET and summarize its applications.

scholarly journals A Single Microphone Capillary-Based System for Measuring the Complex Input Impedance of Musical Wind Instruments

2011 ◽  
Vol 97 (5) ◽  
pp. 819-829 ◽  
Author(s):  
D. B. Sharp ◽  
A. Mamou-Mani ◽  
M. van Walstijn
Keyword(s):  
Input Impedance ◽  
Impedance Measurement ◽  
Wind Instruments ◽  
Basic Principles ◽  
High Impedance ◽  
Calibration Measurement ◽  
Set Up ◽  
The One ◽  
Test Objects ◽  
Impedance Magnitude

Capillary-based systems for measuring the input impedance of musical wind instruments were first developed in the mid-20th century and remain in widespread use today. In this paper, the basic principles and assumptions underpinning the design of such systems are examined. Inexpensive modifications to a capillary-based impedance measurement set-up made possible due to advances in computing and data acquisition technology are discussed. The modified set-up is able to measure both impedance magnitude and impedance phase even though it only contains one microphone. In addition, a method of calibration is described that results in a significant improvement in accuracy when measuring high impedance objects on the modified capillary-based system. The method involves carrying out calibration measurements on two different objects whose impedances are well-known theoretically. The benefits of performing two calibration measurements (as opposed to the one calibration measurement that has been traditionally used) are demonstrated experimentally through input impedance measurements on two test objects and a Boosey and Hawkes oboe.

scholarly journals Extended T-type Inverter

2018 ◽  
Vol 3 (1) ◽  
pp. 55-64
Author(s):  
Jacek Rąbkowski ◽  
Rafał Kopacz
Keyword(s):  
Low Voltage ◽  
Field Effect Transistors ◽  
Schottky Diodes ◽  
Input Voltage ◽  
Neutral Point ◽  
Oxide Semiconductor ◽  
Laboratory Model ◽  
Power Losses ◽  
Power Semiconductor ◽  
Point Potential

Abstract This paper presents a new concept for a power electronic converter - the extended T-type (eT) inverter, which is a combination of a three-phase inverter and a three-level direct current (dc)/dc converter. The novel converter shows better performance than a comparable system composed of two converters: a T-type inverter and a boost converter. At first, the three-level dc/dc converter is able to boost the input voltage but also affects the neutral point potential. The operation principles of the eT inverter are explained and a simulation study of the SiC-based 6 kVA system is presented in this paper. Presented results show a serious reduction of the DC-link capacitors and the input inductor. Furthermore, suitable SiC power semiconductor devices are selected and power losses are estimated using Saber software in reference to a comparative T-type inverter. According to the simulations, the 50 kHz/6 kVA inverter feed from the low voltage (250 V) shows <2.5% of power losses in the suggested SiC metal oxide-semiconductor field-effect transistors (MOSFETs) and Schottky diodes. Finally, a 6 kVA laboratory model was designed, built and tested. Conducted measurements show that despite low capacitance (2 × 30 μF/450 V), the neutral point potential is balanced, and the observed efficiency of the inverter is around 96%.

scholarly journals Cryogenic low-noise amplifiers for measurements with superconducting detectors

2020 ◽  
Vol 11 ◽  
pp. 1316-1320
Author(s):  
Ilya L Novikov ◽  
Boris I Ivanov ◽  
Dmitri V Ponomarev ◽  
Aleksey G Vostretsov
Keyword(s):  
Circuit Design ◽  
Flicker Noise ◽  
High Gain ◽  
Low Noise ◽  
Low Noise Amplifiers ◽  
Voltage Noise ◽  
Noise Spectral Density ◽  
Bipolar Junction Transistor ◽  
Differential Amplifiers ◽  
Junction Transistor

We designed, implemented, and characterized differential amplifiers for cryogenic temperatures based on Si bipolar junction transistor technology. The amplifiers show high gain values of more than 60 dB at 300, 77, and 48 K. The minimum voltage noise spectral density was achieved at 77 K and corresponded to 0.33 nV/Hz0.5 with a flicker noise of 20 Hz. The maximum voltage gain was 70 dB at 77 K for a frequency range from DC to 17 kHz. We experimentally show that the parallel differential circuit design allows for a reduction of the voltage noise from 0.55 to 0.33 nV/Hz0.5 at 77 K.

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