Fig 2 - uploaded by Siming Zuo
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Schematic diagrams of a TMR sensor typical structure and its transfer curve with resistance changes according to the angle of the magnetic field.
Source publication
This paper presents a novel low-noise and high-precision readout circuit for tunnelling magnetoresistive (TMR) array to evaluate the suitability of biomagnetic measurement platform for detection of weak biomagnetic fields. We propose a three operational-amplifier architecture with a high input impedance and an adjustable gain for the fabricated TMR...
Context in source publication
Context 1
... external magnetic field. Tunnelling is a nanoscale effect where electrons can pass through a very thin (sub-nanometre) insulating material under the right condition, exhibiting spinrelated magnetoresistive properties at room temperature. That is called tunnelling magnetoresistance (TMR). The typical structure and its transfer curve are shown in Fig. 2. The TMR sensor comprises two layers of ferromagnetic (FM) material separated by an insulation layer. The top layer is defined as a free layer since its magnetization direction can be changed freely, and the bottom layer is called a pined layer due to its fixed magnetization orientation when the sensor is fabricated. To indicate the ...
Citations
... In a typical Wheatstone bridge system (ex: -Giant magnetoresistance (GMR) [8], [17], [18], Tunneling magnetoresistance (TMR) [10], [11], or pressure sensor [7]) except Hall sensor, the bridge is either composed of two fixed-resistance and two variable resistance [6], or all of the resistance are variable as per Figs. 1(a) and (b) respectively [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. Typically a readout IC for a resistive sensor includes an instrumentation amplifier (IA) or differential difference amplifier (DDA), a filtering stage, and an analogue-to-digital (ADC) for digitizing the output of a bridge sensor [2]. ...
... Post amplification No Yongsu Kwon [5] Ladder, Resistive 12 post amplification Yes Yu-Pin-Hsu [7] Binary weighted, Current Steering 7 before amplification No Sining Pan [9] Seies DAC+ PWM generator 12 before amplification Yes Ayan Mohamed [10], [11] Current steering 11(5) before and No after amplification Siming Zuo [12] -5 between first and Yes second stage amplification From a circuit's perspective, DAC architecture can be binaryweighted [3], binary ladder type [1]. So, there are a lot many possible combinations. ...
Resistive sensors are beneficial for monitoring physical parameters such as temperature, pressure, humidity, or different pressure wave-based biological signals. Traditionally, resistive sensors generate significant low-frequency offset voltage due to their resistance variation with external factors. Offset is responsible for performance degradation and increased power dissipation of the whole system. This brief analyzed the ‘developed offset’ in constant voltage and constant current-based excitation. The programmable current generation technique based on a digital to analog converter (DAC) can eliminate the generated offset effectively. Different variations of DAC and related supporting structures are developed in 0.18µm, 1.8 V process and analyzed for their compensation capability based on parameters like area, power consumption, and ease of implementation. The area of the overall system and no. of bits in DAC are improved by 15% and 2-bit, respectively for the proposed architecture w.r.t state-of-the-art design for an equal amount of offset compensation. However, the complexity of the compensating architecture is increased due to an increase in the supporting architecture of DAC.
... By Combining (4) and (5), we get the magnetic field and GMR element resistance variation relationship in (6). Multiple works are carried out based on the above formulation of resistance variation with incident magnetic field [5]- [9] but combining mathematical modeling, COMSOL simulation, and SPICE-based analysis for AFE design is still in its nascent stage [17]- [18]. Optimizing the GMR sensor probe decreases the complexity and power budget of the signal conditioning electronics. ...
Magnetoplethysmogram (MPG) is typically acquired by placing a giant magnetoresistance sensor (GMR)-magnet system in a blood vessel's (e.g., radial artery) vicinity. This brief analyzed multiple linearizing front ends for the GMR-magnet system. GMR based analog front end's (AFE) gain requirement is derived through COMSOL and MATLAB-based simulation considering the raw signal data. After that, we designed a fully differential difference amplifier (FDDA) in 0.18 µm, 1.8 V process using the SPICE environment for amplification of MPG signals. An automatic calibration method is used for compensating the GMR sensor's offset and lowering it to a few µV level during constant current excitation. This proposed GMR-magnet system is a stepping stone towards non-invasive arterial pulse waveform (APW) detection using the MPG principle, with or without direct skin contact. The DDA achieves open and closed-loop gain of 102 dB and 32 dB, phase margin of 62 • , an IRN of 1.8µV, and a unity-gain frequency of 32kHz, resulting in a closed-loop bandwidth of 800 Hz while dissipating 1.2 µA from a 1.8-V supply.
Biological weak magnetic field detection has gradually become a research hotspot.The miniaturized and high performance magnetic sensor detection system has important application prospects in biomolecular detection, magnetic anomaly detection, aerospace and other fields. Traditional biomolecular detection methods are expensive, time-consuming and low accuracy, and are gradually replaced by new magnetic sensor detection methods. In this study, a biodetection system based on the tunnel magnetoresistive effect sensor is proposed to detect magnetosomes in the following magnetotactic bacteria. The biological detection system is composed of the TMR and the differential amplifier, which is of great significance for the early detection of human cancer in the future. In this paper, a biological detection system is first used to simulate the detection of weak biological magnetic field in energized solenoid. The measurement range of the biological weak magnetic field detection system is ± 30 Oe, and the magnetic induction intensity change of 10nT can be accurately identified. The linear regression equation Y = 0.90926 + 0.00113X (R = 0.99983, P < 0.0001, N = 10) was obtained by amplifying the TMR output signal through a differential amplifier. At the same time, the average number of magnetosomes in magnetotactic bacteria is 22.8, which can satisfy the accurate detection of 103 units of magnetotactic bacteria. By measuring magnetotactic bacteria with different gradient concentrations, the regression equation between magnetotactic bacteria concentration and output voltage is Y = 0.90926 + 0.06732X (R = 0.99838, P < 0.0001, N = 6). This method can detect the biological weak magnetic field quickly and accurately with good recovery and reproducibility.
