scholarly journals Two-Wired Active Spring-Loaded Dry Electrodes for EEG Measurements

Sensors ◽  
2019 ◽  
Vol 19 (20) ◽  
pp. 4572 ◽  
Author(s):  
Seungchan Lee ◽  
Younghak Shin ◽  
Anil Kumar ◽  
Kiseon Kim ◽  
Heung-No Lee
Keyword(s):  
Alpha Rhythm ◽  
Electrical Coupling ◽  
Equivalent Circuit Model ◽  
Critical Issue ◽  
Electrode System ◽  
Low Noise ◽  
Contact Impedance ◽  
Noise Spectral Density ◽  
Input Capacitance ◽  
Dry Electrode

Dry contact electrode-based EEG acquisition is one of the easiest ways to obtain neural information from the human brain, providing many advantages such as rapid installation, and enhanced wearability. However, high contact impedance due to insufficient electrical coupling at the electrode-scalp interface still remains a critical issue. In this paper, a two-wired active dry electrode system is proposed by combining finger-shaped spring-loaded probes and active buffer circuits. The shrinkable probes and bootstrap topology-based buffer circuitry provide reliable electrical coupling with an uneven and hairy scalp and effective input impedance conversion along with low input capacitance. Through analysis of the equivalent circuit model, the proposed electrode was carefully designed by employing off-the-shelf discrete components and a low-noise zero-drift amplifier. Several electrical evaluations such as noise spectral density measurements and input capacitance estimation were performed together with simple experiments for alpha rhythm detection. The experimental results showed that the proposed electrode is capable of clear detection for the alpha rhythm activation, with excellent electrical characteristics such as low-noise of 1.131 μVRMS and 32.3% reduction of input capacitance.

scholarly journals Validation of a wireless dry electrode system for electroencephalography

2015 ◽  
Vol 12 (1) ◽  
Author(s):  
Sarah N Wyckoff ◽  
Leslie H Sherlin ◽  
Noel Larson Ford ◽  
Dale Dalke
Keyword(s):  
Electrode System ◽  
Dry Electrode

scholarly journals Low-Frequency Noise and Microplasma Analysis for c-Si Solar Cell Characterization

2012 ◽  
Vol 2012 ◽  
pp. 1-5 ◽  
Author(s):  
Jiří Vanek ◽  
Jan Dolensky ◽  
Zdenek Chobola ◽  
Mirek Luňák ◽  
Aleš Poruba
Keyword(s):  
Solar Cells ◽  
Solar Cell ◽  
Conversion Efficiency ◽  
Low Frequency ◽  
Low Noise ◽  
Frequency Noise ◽  
Noise Spectral Density ◽  
Selective Emitter ◽  
Noise Spectroscopy ◽  
Cell Conversion

This paper brings the comparison of solar cell conversion efficiency and results from a noise spectroscopy and microplasma presence to evaluate the solar cell technology. Three sets of monocrystalline silicon solar cells (c-Si) varying in front side phosphorus doped emitters were produced by standard screen-printing technique. From the measurements it follows that the noise spectral density related to defects is of 1/ftype and its magnitude. It has been established that samples showing low noise feature high-conversion efficiency. The best results were reached for a group solar cells with selective emitter structure prepared by double-phosphorus diffusion process.

scholarly journals Low Noise, High Input Impedance Digital-Analog Hybrid Offset Suppression Amplifier for Wearable Dry Electrode ECG Monitoring

Electronics ◽  
2020 ◽  
Vol 9 (1) ◽  
pp. 165 ◽  
Author(s):  
Weilin Xu ◽  
Taotao Wang ◽  
Xueming Wei ◽  
Hongwei Yue ◽  
Baolin Wei ◽  
...  
Keyword(s):  
Input Impedance ◽  
Electronic Device ◽  
Gain Control ◽  
Low Noise ◽  
Instrumentation Amplifier ◽  
High Input ◽  
High Input Impedance ◽  
Capacitively Coupled ◽  
Dry Electrode ◽  
Long Time

The portable real-time electrocardiogram (ECG) is a convenient and promising electronic device for cardiovascular diseases patients. However, unlike wet gel electrodes in traditional clinical applications, dry electrodes are competent for comfortable long-time wearing and can prevent skin ulceration. Its ultra-high source impedance and electrode offset (EOS) make traditional chopper amplifiers with low input impedance and limited EOS range difficult to apply to this area. To overcome these challenges, this paper proposes a novel chopper amplifier topology. This architecture includes a gain control loop, a ripple reduction loop, and a DC-servo loop (DSL). The proposed sampling input stage and digital-analog hybrid DSL are employed to boost input impedance and extend the EOS handing range. Designed with a 0.18 µm 1P6M 1.8 V CMOS salicide process, the proposed chopper capacitively coupled instrumentation amplifier achieves an ultra-high input impedance of 120 GΩ (<0.05 Hz) or 2.1 GΩ (0.6~250 Hz), an EOS handing range of ±325 mV and a low noise of 1.9 μVrms at 0.6~250 Hz. It occupies an area of 0.36 mm2 and only consumes a quiescent current of 11 μA.

scholarly journals An efficient design of 45-nm CMOS low-noise charge sensitive amplifier for wireless receivers

2022 ◽  
Vol 12 (2) ◽  
pp. 1274
Author(s):  
Islam T. Almalkawi ◽  
Ashraf H. Al-Bqerat ◽  
Awni Itradat ◽  
Jamal N. Al-Karaki
Keyword(s):  
Power Consumption ◽  
Signal To Noise Ratio ◽  
Cmos Technology ◽  
Channel Length ◽  
Low Noise ◽  
Efficient Design ◽  
Wireless Devices ◽  
Noise Spectral Density ◽  
Wireless Applications ◽  
Amplifier Design

<p>Amplifiers are widely used in signal receiving circuits, such as antennas, medical imaging, wireless devices and many other applications. However, one of the most challenging problems when building an amplifier circuit is the noise, since it affects the quality of the intended received signal in most wireless applications. Therefore, a preamplifier is usually placed close to the main sensor to reduce the effects of interferences and to amplify the received signal without degrading the signal-to-noise ratio. Although different designs have been optimized and tested in the literature, all of them are using larger than 100 nm technologies which have led to a modest performance in terms of equivalent noise charge (ENC), gain, power consumption, and response time. In contrast, we consider in this paper a new amplifier design technology trend and move towards sub 100 nm to enhance its performance. In this work, we use a pre-well-known design of a preamplifier circuit and rebuild it using 45 nm CMOS technology, which is made for the first time in such circuits. Performance evaluation shows that our proposed scaling technology, compared with other scaling technology, extremely reduces ENC of the circuit by more than 95%. The noise spectral density and time resolution are also reduced by 25% and 95% respectively. In addition, power consumption is decreased due to the reduced channel length by 90%. As a result, all of those enhancements make our proposed circuit more suitable for medical and wireless devices.</p>

A closed-loop readout interface for MEMS accelerometer with time-multiplexing electrostatic force feedback

2019 ◽  
Vol 33 (35) ◽  
pp. 1950447 ◽  
Author(s):  
Zhi Yuan Sun ◽  
Liang Yin ◽  
Jian Hai Yu
Keyword(s):  
Closed Loop ◽  
Force Feedback ◽  
Electrostatic Force ◽  
Critical Issue ◽  
Feedback Signal ◽  
Noise Spectral Density ◽  
Mems Accelerometer ◽  
Loop Transfer Function ◽  
Seismic Acquisition ◽  
Voltage Feedback

The noise and linearity performance of a MEMS accelerometer is a critical issue for land seismic acquisition applications. Incorporating closed-loop force feedback is an effective way to enhance those performances. However, additional electrode to exert the electrostatic force is typically not available and residue displacement of proof mass would introduce significant nonlinearity to the closed-loop transfer function, impairing the efficiency of the method. This paper proposes a switched-capacitor closed-loop readout interface for MEMS accelerometer which greatly alleviates those problem. First, the proposed system incorporates a time-multiplexing technique, thus the sensing and force feedback can be realized using the same electrode and get separated in time sequence. Furthermore, the cross-coupling of high-voltage feedback signal and weak sensing signal can be minimized. Second, a correlated double sampling (CDS) technique and a PID control mechanism is introduced in the loop. Thus, the two sources of residue displacement: interface mismatch and insufficient loop gain can be well-suppressed. The test results show that the proposed closed-loop MEMS accelerometer can achieve an SNR better than 120 dB, with an in-band noise spectral density lower than 500 ng/Hz[Formula: see text].

scholarly journals Flexible Multi-Layer Semi-Dry Electrode for Scalp EEG Measurements at Hairy Sites

Micromachines ◽  
2019 ◽  
Vol 10 (8) ◽  
pp. 518 ◽  
Author(s):  
Haoqiang Hua ◽  
Wei Tang ◽  
Xiangmin Xu ◽  
David Dagan Feng ◽  
Lin Shu
Keyword(s):  
Temporal Correlation ◽  
Acquisition Time ◽  
Eeg Monitoring ◽  
Foam Layer ◽  
Contact Impedance ◽  
Lower Electrode ◽  
Scalp Eeg ◽  
Dry Electrodes ◽  
Dry Electrode

One of the major challenges of daily wearable electroencephalogram (EEG) monitoring is that there are rarely suitable EEG electrodes for hairy sites. Wet electrodes require conductive gels, which will dry over the acquisition time, making them unstable for long-term EEG monitoring. Additionally, the electrode–scalp impedances of most dry electrodes are not adequate for high quality EEG collection at hairy sites. In view of the above problems, a flexible multi-layer semi-dry electrode was proposed for EEG monitoring in this study. The semi-dry electrode contains a flexible electrode body layer, foam layer and reservoir layer. The probe structure of the electrode body layer enables the electrode to work effectively at hairy sites. During long-term EEG monitoring, electrolytes stored in the reservoir layer are continuously released through the foam layer to the electrode–scalp interface, ensuring a lower electrode–scalp contact impedance. The experimental results showed that the average electrode–scalp impedance of the semi-dry electrode at a hairy site was only 23.89 ± 7.44 KΩ at 10 Hz, and it was lower than 40 KΩ over a long-term use of 5 h. The electrode performed well in both static and dynamic EEG monitoring, where the temporal correlation with wet electrode signals at the hairy site could reach 94.25% and 90.65%, respectively, and specific evoked EEG signals could be collected. The flexible multi-layer semi-dry electrode can be well applied to scalp EEG monitoring at hairy sites, providing a promising solution for daily long-term monitoring of wearable EEGs.

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