Voltage Noise Research Articles

Uncertainty analysis of selected standard methods in battery measurement technology

Measuring the state of batteries and their change over time is essential during research and development. A number of standard test methods are available to determine specific cell parameters, such as capacitance, internal resistance, coulombic efficiency, etc. Although these methods have been in use for a long time, a thorough analysis of the uncertainties associated with them – especially when using high-precision measuring equipment – is still lacking.Therefore, a primary goal of this work is to close this gap. For each method, the results of the uncertainty analysis are divided into a variable part (noise, jitter) and a constant part (absolute accuracy). In addition, the theoretical analysis is accompanied by practical measurement results from a high-precision measurement hardware, demonstrating what is currently possible with state-of-the-art equipment.The constant part of the uncertainty is mainly limited by the used calibration equipment. For the variable part of uncertainty, the situation is somewhat more varied. Using a battery temperature control with a variability of only ±0.1∘C, capacity, capacity change and coulombic efficiency still show a strong influence on the prevailing small temperature variations. For the voltage analysis methods (differential capacity and voltage analysis) the predominate factor is voltage noise and drift.

Modified RPWM Strategy Based on Level-Shifted Random Carrier and Power Balance to Reduce the PWM Voltage Noise in Three-Phase CHB Inverters

Aimed at the pulse width modulation (PWM) voltage noise and power imbalance in three-phase cascaded H-Bridge (CHB) inverters, a modified random PWM (RPWM) strategy, named the power-balanced RPWM (PB-RPWM) strategy, is proposed in this paper. The PB-RPWM strategy mainly includes three steps: (1) random pulse signals are generated by compared modulation wave with level-shifted random carriers; (2) the random pulse signals are circularly distributed between CHB units by a logic operation method, and then the driving pulse signals of switching devices are produced; (3) the driving pulse signals are used to control the inverter. Under the PB-RPWM strategy, the spectra of the line voltage become uniform and continuous, that is, the PWM voltage noise of the line voltage can be effectively reduced. The output voltage of a single H-bridge unit can contain three basic voltages within 3/2 TA, that is, the power balance between CHB units can be realized. When compared with conventional non-random and random PWM strategies, the PB-RPWM strategy has a lower PWM voltage noise and smaller total harmonic distortion (THD). When compared with the level-shifted PWM (LS-PWM) strategy, the PB-RPWM strategy has a balanced power performance. The effectiveness and feasibility of the PB-RPWM strategy is verified by abundant simulations and experiments.

Low On-State Voltage and EMI Noise 4H-SiC IGBT With Self-Biased Split-Gate pMOS

A 15-kV-scale 4H-SiC insulated-gate bipolar transistor (IGBT) with a self-biased split-gate pMOS (SGPMOS) is proposed and simulated in this work. By introducing the SGPMOS, the proposed IGBT forms a hole barrier in the ON-state and a hole extraction path during the turn-on and turn-off transient, respectively. Compared to GS IGBT, the ON-state voltage ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{\text {ON}}{)}$ </tex-math></inline-formula> of the SGPMOS IGBT is decreased by 54.95% for the same turn-off loss ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${E}_{\text {off}}$ </tex-math></inline-formula> ). Meanwhile, compared with pMOS IGBT, the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${C}$ </tex-math></inline-formula> – <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}$ </tex-math></inline-formula> and gate charge ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Q}_{g}{)}$ </tex-math></inline-formula> characteristics exhibit that the Miller capacitance ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${C}_{\text {gc}}{)}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Q}_{g}$ </tex-math></inline-formula> of the SGPMOS IGBT are reduced by 56.60% and 35.85%, respectively. Moreover, SGPMOS can extract the hole accumulated both under the gate oxide and in the P-shield region during the turn-on transient. This diminishes reverse displacement current ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I}_{G\_{}{\text {dis}}}{)}$ </tex-math></inline-formula> , contributing to low electromagnetic interference (EMI) noise. Simulation results demonstrate that, compared to pMOS IGBT, the SGPMOS IGBT achieves better controllability in peak turn-on current ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I}_{\text {max}}{)}$ </tex-math></inline-formula> and turn-on <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{d}{I}_{C}/\text{d}{t}$ </tex-math></inline-formula> , featuring a 52.75% lower maximum reverse recovery <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{d}{V}_{\text {KA}}/\text{d}{t}$ </tex-math></inline-formula> for the same turn-on loss ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${E}_{\text {on}}{)}$ </tex-math></inline-formula> .

A Two-Step Approach for the Analysis of Bulk Current Injection Setups Involving Multiwire Bundles

In this work, a two-step procedure to predict maximum (worst-case scenario) and minimum (best-case scenario) noise levels induced by bulk current injection (BCI) at the terminal sections of a wiring harness is presented. To this end, common mode (CM) and differential mode (DM) quantities are introduced by a suitable modal transformation, and equivalent modal circuits are derived, where CM (dominant mode) into DM (secondary mode) conversion is modelled by induced sources included into the DM circuit. The procedure initially foresees the solution of the CM circuit to provide input data for subsequent solution of the DM circuit. Such a two-step approach is then used to develop a probabilistic–possibilistic framework for computationally-efficient estimation of lower and upper boundaries to the variability of the noise voltages induced at the bundle terminations. To this end, random uncertainty affecting certain setup parameters is addressed through probability theory, whereas epistemic uncertainty is represented via possibility theory. Accuracy and computational efficiency of the proposed two-step method are assessed by examples involving seven and nineteen wire harnesses.

Relationship between epi-wafer photoluminescence and focal plane array performances of InGaAs detectors

The relationship between photoluminescence properties of InGaAs detector epi-wafers and the performances of focal plane arrays has been established according to the measurements of various samples. The average signal, dark signal and noise of the fabricated focal plane arrays were characterized and correlated to the photoluminescence intensities and nonuniformities of the epi-wafers. The average response signal is increased as the increased photoluminescence. The signal nonuniformity and dark signal are markedly related to nonuniformity of photoluminescence intensity, while the noise voltages are not correlated to photoluminescence results. The microwave photoconductance decay measurements reveal that the epi-wafers with stronger photoluminescence intensity has longer minority carrier lifetime. This work supplies a feasible pathway to evaluate and predict the performances of focal plane arrays fabricated by InGaAs detector epi-wafers before device processing.

FPGA-Based Decision Support System for ECG Analysis

The high mortality rate associated with cardiac abnormalities highlights the need of accurately detecting heart disorders in the early stage so to avoid severe health consequence for patients. Health trackers have become popular in the form of wearable devices. They are aimed to perform cardiac monitoring outside of medical clinics during peoples’ daily lives. Our paper proposes a new diagnostic algorithm and its implementation adopting a FPGA-based design. The conceived system automatically detects the most common arrhythmias and is also able to evaluate QT-segment lengthening and pulmonary embolism risk often caused by myocarditis. Debug and simulations have been carried out firstly in Matlab environment and then in Quartus IDE by Intel. The hardware implementation of the embedded system and the test for the functional accuracy verification have been performed adopting the DE1_SoC development board by Terasic, which is equipped with the Cyclone V 5CSEMA5F31C6 FPGA by Intel. Properly modified real ECG signals corrupted by a mixture of muscle noise, electrode movement artifacts, and baseline wander are used as a test bench. A value of 99.20% accuracy is achieved by taking into account 0.02 mV for the root mean square value of noise voltage. The implemented low-power circuit is suitable as a wearable decision support device.

A low noise double-sided inductive method for measuring the critical current density of superconducting materials

The critical current density Jc is an important indicator of superconducting materials in practical applications. The third harmonic voltage method is a simple, efficient, and damage-free method for measuring Jc of high-temperature superconducting films. To this end, a double-sided measurement system was hereby proposed to reduce harmonic voltage noise, thereby more effectively measuring the Jc of high-temperature superconducting REBa2Cu3O7-δ (RE, rare earth element) films using the third harmonic voltage method. By integrating the electromagnetic shielding effect and the 2-coil measurement system, this system reduces the harmonic voltage noise in the pickup coil using the Meissner effect, thereby improving the signal-to-noise ratio. The experimental results show that when Jc is measured in the range of 100 Hz to 1000 Hz, the signal-to-noise ratio of the double-sided device increases by 10 dB to 20 dB, higher than that of the 2-coil measurement system. In addition, this new system increases the measurement bandwidth, and makes it possible to conduct low-frequency measurement in the future.

Fluctuation-dissipation in thermoelectric sensors

Thermoelectric materials exhibit correlated transport of charge and heat. The Johnson-Nyquist noise formula 4k B T R for the spectral density of voltage fluctuations accounts for fluctuations associated solely with Ohmic dissipation. Applying the fluctuation-dissipation theorem, we generalize the Johnson-Nyquist formula for thermoelectrics, finding an enhanced voltage fluctuation spectral density 4k B T R(1 + Z D T) at frequencies below a thermal cut-off frequency f T , where Z D T is the dimensionless thermoelectric device figure of merit. The origin of the enhancement in voltage noise is thermoelectric coupling of temperature fluctuations. We use a wideband , integrated thermoelectric micro-device to experimentally confirm our findings. Measuring the Z D T enhanced voltage noise, we experimentally resolve temperature fluctuations with a root mean square amplitude of at a mean temperature of 295 K. We find that thermoelectric devices can be used for thermometry with sufficient resolution to measure the fundamental temperature fluctuations described by the fluctuation-dissipation theorem.

Ionic liquid gated unipolar inverters with tunable switching voltage and excellent noise margin

Solution-processable organic semiconductor-based ambient-stable and flexible-compatible ionic liquid-gated inverter with a gain &gt;10 and noise margin ≈60% paves the way for the integration of ionic liquid-gated logic components into circuits.

Parametric Analysis of Electrostatic Comb Drive for Resonant Sensors Operating under Atmospheric Pressure

The microelectrostatic comb resonator’s issues with high driving voltage and strong feed‐through coupling noise limit its practical use. In earlier studies, the design and structural optimization of microcomb resonators generally focused on lowering beam stiffness and raising electrostatic force density to enhance resonance displacement and lower driving voltage. However, for a microresonator that performs high‐speed resonance in the air, it is required to consider the three influencing elements of the electrostatic field, structural mechanics, and fluid mechanics to achieve the best dynamic resonance amplitude. In this paper, the parametric analysis of the comb‐driven resonator is carried out. First, the comb‐driven electrostatic force and all air‐damping terms are investigated using an electrostatic force analytical model considering edge effects, a damping analytical model simplified based on the thin‐film damping model, and the finite element model. The analysis results agree with the simulated results. To more accurately quantify the dynamic electrostatic force and damping coefficient, the electrostatic–structure–fluid three‐field indirect coupling model was used, and the law of the resonant amplitude of the resonator as a function of the structural parameters was obtained. The results show that, for the electrostatic comb resonator that oscillates at atmospheric pressure, to obtain a high‐voltage driving efficiency, a thin polysilicon film can be used to design narrow comb fingers that are dense in the vertical direction and loose in the lateral direction. To validate the accuracy of the model and the results of parameter analysis, an electrostatic comb‐drive resonator with shapes optimized from numerical simulations was fabricated. The results show that the driving efficiency is enhanced by 102%, with the chip area increased by 29%, which shows the superiority of parameter optimization.

An Automated Design Methodology for Ring Voltage-Controlled Oscillators in Nanometer CMOS Technologies

This paper presents a design automation methodology for ring voltage-controlled oscillators (RVCOs) with their realistic and physical characteristics captured. With multiple sets of input constraints such as target frequency, phase noise, and control voltage range, the proposed algorithm automatically finds the design candidates that satisfy the target constraints, by running iterative post-layout simulations with auto-generated layouts and testbenches. The number of post-layout simulations is significantly reduced by the backtracking algorithm that observes the simulation results and determines the search direction. The proposed algorithm is applied to generate RVCOs in 40-nm planar and 7-nm FinFET technologies for DDR5 applications, and it turns out the proposed methodology produces sets of design parameters that meet the target specification in multiple technologies.

Programmable precision voltage reference source for space-based gravitational wave detection

Gravitational wave detection plays an important role in exploring the universe and opening up a new chapter for multi-messenger astronomy. As the most common device used for space and ground-based gravitational wave detection, large-scale laser interferometer requires a low-noise laser as a beam source. The noise of the laser can be suppressed by utilizing the optoelectronic negative-feedback noise reduction technology to improve the sensitivity of large-scale laser interferometer. The optoelectronic negative-feedback control system can suppress laser noise by subtracting the photodetector signal from the voltage reference signal, and then calculating the modulated signal by a proportional integral differentiator to control the output power of the pump current driver. Since the photodetector signal is affected by the laser intensity, its output voltage varies within a certain range, which requires that the output voltage of the voltage reference source signal is variable. In addition, the performance of the voltage reference directly affects the overall performance of the feedback control loop, therefore it is the lower limit of laser noise suppression. We develop a high-precision low-noise program-controlled voltage reference by selecting low-noise reference chip and digital-to-analog conversion chip, designing external control circuit, using low-temperature drift coefficient components and using temperature control and electromagnetic shielding. The digital-to-analog conversion is controlled through the FPGA module programming to accurately realize the reference voltage change. The output voltage range of the developed voltage reference source is from negative 10 V to positive 10 V and the minimal precision of the voltage variation is 20 bit. The voltage noise spectral density of the developed voltage reference is below &lt;inline-formula&gt;&lt;tex-math id="M1"&gt;\begin{document}$9.6 \times 1{0^{ - 6}}/\sqrt {\rm Hz}$\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20222119_M1.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20222119_M1.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt; and the noise performance of the reference source is less than the laser intensity noise in the space-based gravitational wave frequency band. The developed voltage reference source provides an important technical support for laser intensity noise suppression in gravitational wave detection.

Refined DC and Low-Frequency Noise Characterization at Room and Cryogenic Temperatures of Vertically Stacked Silicon Nanosheet FETs

In this work, two types of gate-all-around (GAA) vertically stacked silicon nanosheet (NS) FETs are investigated, the main difference being the vertical distance between the stacked NSs. Principal electrical parameters are estimated at room and liquid nitrogen temperatures using a refined <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Y}$ </tex-math></inline-formula> -function methodology, the main advantage being that no extra iterative steps are necessary. The results are confirmed using other derivative dc parameter estimation methodologies. Low-frequency noise measurements evidence variability of the flat-band voltage noise and correlation between the noise level and the low field mobility. The dominant flicker noise mechanism is related to the correlated mobility and carrier number fluctuation mechanism with access resistance noise contribution in very strong inversion. The impact of the access resistance on the estimation of the Coulomb scattering coefficient is evidenced.

Method to improve critical current density measurement of superconducting materials

The critical current density Jc is an important indicator of superconducting materials in practical applications. And the third harmonic voltage method is a simple, efficient and damage-free method for measuring Jc of high-temperature superconducting films. In order to more effectively measure the Jc of high-temperature superconducting REBa2Cu3O7-δ films and improve the signal-to-noise ratio based on the third harmonic voltage method, a double-sided measurement method was hereby proposed. By integrating the electromagnetic shielding effect and the 2-coil measurement system, the Meissner effect was used to reduce the harmonic voltage noise in the pickup coil. Comparing the double-sided measurement system using the new method to the 2-coil measurement system, the signal-to-noise ratio increases by 10 dB to 20 dB in the case of a Jc measured in the frequency range from 100 Hz to 1000 Hz. The bullet points of the method can be listed as:•The noise in the pickup coil is reduced and the signal-to-noise ratio is improved in the frequency range from 100 Hz to 1000 Hz by using the Meissner effect.•The measurement bandwidth is increased, making it possible to conduct low-frequency measurement in the future by the double-sided measurement method.•The method provides an improvement direction for superconducting thin films with a high critical current density in the future.

ОПТИМІЗАЦІЯ АНАЛОГОВОГО МОДУЛЮ ЗА ШУМОВИМИ ХАРАКТЕРИСТИКАМИ У БОРТОВОМУ ДЕТЕКТОРІ РЕЄСТРАТОРА-АНАЛІЗАТОРА ДЛЯ ІДЕНТИФІКАЦІЇ ЗАРЯДЖЕНИХ ЧАСТИНОК

In analog amplifiers of weak signals, the question arises of finding the optimal signal/noise ratio based on noise characteristics for further discretization of the signal by digital methods. Using computer simulations is not a solution to this problem. Because the developers of electronics simulators do not reveal the progress of calculations as usual, or provide the opportunity to independently enter formulas for calculation with the unpredictable probability of forecasting results.In current work, a method for calculating and optimizing the noise level has been developed. It is proposed to be used for debugging circuits based on operational amplifiers, which will save time and money during further testing and optimization of the circuit before its manufacture. And the developers in the datasheet specify the noise parameters without taking into account all the cascade (with open feedback loop, etc.). That is why, a method is needed that takes into account the noise parameters of the switching circuit. The key parameters of the cascades, which have an impact on the reliability of sampling, are among other types: inherent noises of operational amplifiers and thermal noises of the elements of the switching circuit, which are optimized by reduction to a single basis and checked for compliance with the research objectives. In addition, the sequence of actions that establishes the accuracy of discretization of the system with the influence of noise voltage is described.As a result, the solution of the noise level minimization problem by simplified computer calculation is accelerated. Signal-to-noise ratio optimization achieved by non-linear programming method.The proposed method can be used both for analysis discrete and integrated circuits. The results of the work have been used for optimization of the existing analog scheme of the small-caliber spectrometer MiRA_ep that is planning to be launched into low near-Earth orbit to study the nature of the high-energy electron and proton microbursts.

The Design of An LDO Regulator

In today’s modern systems on chip (SOCs), a crucial power management circuit is the low-dropout (LDO) regulator. Of course, the need for supply voltage regulation, goes back many years in the past since the circuits have been designed. Today, LDO based voltage regulators are frequently used in a number of mixed-signal systems to produce local supply voltages that feed different building blocks. LDOs try to isolate the noise of the circuit and noise from the global supply and try to reduce their effect on device performance. For the state of desired achievement, each LDO’s architecture is circuited to the specific cell it feeds. An LDO designed to feed a flash analog-to-digital converter, for instance, differs greatly from one designed to input a VCO. In this paper, we direct an LDO for a VCO of 5-GHz LC and point the particulars of 1.2 V as input voltage, produces 1V as output voltage, 5 mA of maximum output current, power supply rejection greater than 40 dB up to 10 MHz and noise voltage present at output that is less than 25nV/√Hz at 1 MHz.

Impact of the channel doping on the low-frequency noise of gate-all-around silicon vertical nanowire pMOSFETs

In this work, the impact of the channel doping density on the low-frequency noise of silicon Gate-All-Around (GAA) Vertical Nanowire (VNW) pMOSFETs on Silicon-on-Insulator (SOI) substrates will be described and discussed. It is demonstrated that the dominant fluctuation mechanism of the 1/f noise in the subthreshold regime changes from number (Δn) to mobility (Δμ) fluctuations with increasing p-type doping density of the silicon nanowires. At the same time, the lowest input-referred voltage noise Power Spectral Density is observed for an intermediate boron concentration in the nanowire of 5 × 1018 cm−3.

Grid-integrated single phase solar PV system employed with single switch high gain boost converter

• This paper deals with a grid-integrated single phase solar photovoltaic system (GISPSPS) employed with a single switched based high gain boost converter. The significant contributions in this paper are; • The dynamic model of HGBC including effective series resistance (ESR) of passive elements is developed for improving accuracy with slight increase in complexity of model. Then its stability analysis is carried out under different solar irradiations (i.e. 300, 500, 800 and 1000 W/m 2 ) using an eigenvalue plot. • The HGBC control is obtained using the sliding mode control (SMC) for PPE under change in solar irradiations. In proposed SMC only two sensing signals PV panel voltage and current (i.e. v pv and i pv ) are needed for PPE in comparison to three sensing signals PV panel voltage, current and DC link voltage (i.e. v pv , i pv and v dc ) require in SMC of ref. [10] . • The control of FBVSC is obtained by a F i OGI controller. The F i OGI provides noise-less extraction of synchronization signal, under presence of DC offset and noise in grid voltage. However, FOGI used in ref. [10] exhibits poor performance under presence of noise in grid supply voltage. This paper presents a grid-integrated single phase solar photovoltaic (PV) system (GISPSPS) with its modeling, design and control. The GISPSPS consists of a single switch based high gain boost converter (HGBC) and full bridge voltage source converter (FBVSC). The HGBC, boost the low PV panel voltage and extracts the optimum PV power. The HGBC allows high voltage conversion ratio and possesses less voltage stresses on power devices. The optimum PV power is extracted via a sliding mode control (SMC) strategy that generates the switching signal for the switch of HGBC. The FBVSC delivers PV power to the single phase utility grid, as well as load connected at point of interfacing (POI). A fifth order generalized integrator (F i OGI) is developed for FBVSC control to ensure harmonic suppression and DC offset rejection capability during extraction of fundamental grid voltage. Experimental validation of proposed GISPSPS and its control is also verified.

Demonstration of High-Performance GaN-Based Hall Sensors on Si Substrate by Simulation and Experiment Verification

This work demonstrates high-performance wide bandgap GaN-based Hall sensors by theoretical simulation and experimental verification on 6-in wafer. Compared with the conventional fourfold rotationally symmetric cross-shaped structure, the twofold symmetric one has more flexible parameter selection and is able to exhibit better overall performances. The effects of different input and output aspect ratios on the device characteristics are investigated in detail. The simulation data show that the geometric factor and sensitivity of the devices are obviously improved with the increase of the aspect ratio of the input and output terminals, which is also demonstrated by the experimental results from the fabricated Hall sensors. The temperature drift coefficient is found to be less than 100 ppm/K in a wide temperature range of 300–675 K, and the minimum offset voltage is only 52 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{V}$ </tex-math></inline-formula> when the input current is kept at 1.0 mA. In addition, the angle- and noise-related characteristics of the devices are also investigated, and the root-mean-square voltage noise is determined to be <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.48~\mu \text{V}$ </tex-math></inline-formula> . Finally, the good uniformity of the 6-in wafer was verified. The low working noise and good temperature stability in a wide temperature range endow the fabricated GaN-based magnetic sensors with promising applications in harsh and high-temperature environments.

Frequency division multiplexing readout of a transition edge sensor bolometer array with microstrip-type electrical bias lines.

We demonstrate multiplexed readout of 43 transition edge sensor (TES) bolometers operating at 90 mK using a frequency division multiplexing (FDM) readout chain with bias frequencies ranging from 1 to 3.5MHz and a typical frequency spacing of 32kHz. We improve the previously reported performance of our FDM system by two important steps. First, we replace the coplanar wires with microstrip wires, which minimize the cross talk from mutual inductance. From the measured electrical cross talk (ECT) map, the ECT of all pixels is carrier leakage dominated. Only five pixels show an ECT level higher than 1%. Second, we reduce the thermal response speed of the TES detectors by a factor of 20 by increasing the heat capacity of the TES, which allows us to bias all TES detectors below 50% in transition without oscillations. We compare the current-voltage curves and noise spectra of the TESs measured in single-pixel mode and multiplexing mode. We also compare the noise equivalent power (NEP) and the saturation power of the bolometers in both modes, where 38 pixels show less than 10% difference in NEP and 5% difference in saturation power when measured in the two different modes. The measured noise spectrum is in good agreement with the simulated noise based on measured parameters from an impedance measurement, confirming that our TES is dominated by phonon noise.