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Yang Z.,University of Hong Kong | Siu S.-L.,University of Hong Kong | Siu S.-L.,Canaan Semiconductor Ltd | Tam W.-S.,Canaan Semiconductor Ltd | And 6 more authors.
IEEE Transactions on Magnetics | Year: 2014

This paper proposed an analytical model on the deterioration of magnetic sensitivity of sectorial split-drain magnetic field-effect transistors (SD-MAGFETs). The deterioration is governed by the trap fill rate at the channel boundary traps, which is geometric dependent. Experimental results are presented which show good consistency with the analytical derivation. The deterioration is the most severe at a sector angle of 54.6°, which shows a design tradeoff with sensing hysteresis. Design guidelines for sectorial SD-MAGFET to obtain high sensitivity hysteresis and slow sensitivity deterioration are also presented which provide important information for efficient design. © 2013 IEEE.


Tam W.-S.,Canaan Semiconductor Ltd | Kok C.-W.,Canaan Semiconductor Ltd | Lai S.-F.,City University of Hong Kong | Wong H.,City University of Hong Kong
IEEE Region 10 Annual International Conference, Proceedings/TENCON | Year: 2016

A compact model of the loss tangent of the vacuum dielectric capacitor (VDC) in terms of the size of the VDC, capacitance, and ratio of the width of the boundary sealant to the width of the top electrode is presented in this paper. An analytical tool that can determine the optimal size of a VDC to achieve the desired trade-off between the capacitance and loss tangent is described. Although the VDC with a single type of sealant was used as an example to illustrate the idea, the presented methodology is general and can be applied for VDCs constructed with other sealant materials. © 2015 IEEE.


Siu S.-L.,University of Hong Kong | Tam W.-S.,Canaan Semiconductor Ltd | Kok C.-W.,Canaan Semiconductor Ltd | Lai S.-F.,City University of Hong Kong | And 2 more authors.
IEEE Region 10 Annual International Conference, Proceedings/TENCON | Year: 2016

In this paper, the sensitivity distortion of Hall plate based and split-drain magnetic field effect transistor (SSD-MAGFET) based magnetic sensors under the alternating magnetic field is investigated. Based on the outputs of the both hall plate based and SSD-MAGFET based sensors are sinusoidal functions of displacement of a rotating magnetic field strength, we propose to analyze the sensitivity of the sensors by spectral analysis. The empirical results show that conventional Hall plate based sensor suffers from greater spectral distortion when compared to that of SSD-MAGFET based sensors, which implies SSD-MAGFET based sensors can achieve better accuracy in high speed application without the needs of charge accumulation. © 2015 IEEE.


Wong O.-Y.,City University of Hong Kong | Wong H.,City University of Hong Kong | Tam W.-S.,Canaan Semiconductor Ltd | Kok C.-W.,Canaan Semiconductor Ltd
International Journal of Circuit Theory and Applications | Year: 2015

A 4× charge pump using exponential topology is proposed and implemented. Comparing to the conventional implementations, the proposed circuit suppresses the reverse current effectively without using different threshold-voltage transistors and additional capacitors. Also, the body effect found in the charge transfer switches is eliminated. The proposed charge pump is analyzed with the state-space method and fabricated using 0.35 μm complementary metal-oxide-semiconductor process. Results show that the output voltages close to the ideal one, and a maximum power efficiency of 95% was recorded. Copyright © 2013 John Wiley & Sons, Ltd.


Wong O.-Y.,City University of Hong Kong | Wong H.,City University of Hong Kong | Tam W.-S.,Canaan Semiconductor Ltd | Kok C.-W.,Canaan Semiconductor Ltd
Electronics Letters | Year: 2014

The loss estimation in a switched-capacitor DC-DC converter has caused much controversy because of the uncertainty of the contribution of device parasitics to the power efficiency of a converter. Beginning from a simple equivalent circuit model, a closed-form solution to the maximum achievable power efficiency of a converter in which both the effects of parasitic resistance and capacitance are taken into account is presented. It has been observed that the peak power efficiency of a Dickson charge pump depends mainly on the equivalent parasitic capacitance of a given technology and its operation mode, which is governed by the choices of the coupling capacitance, onresistance of the switch, as well as the operation frequency of the circuit. © The Institution of Engineering and Technology 2014.

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