Browsing by Author "Hsu, Wei-Chou"

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A novel dilute antimony channel In0.2Ga0.8AsSb/GaAs HEMT
(2007-02-01)
Su, Ke-Hua
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Hsu, Wei-Chou
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Lee, Ching-Sung
;
Wu, Tsung-Yeh
;
Wu, Yue-Han
This letter reports, for the first time, a high-electron mobility. transistor (HEMT) using A dilute antimony In0.2Ga0.8AsSb channel, which is grown by a molecular-beam epitaxy system. The interfacial quality within the InGaAsSb/GaAs quantum well of the HEMT device was effectively improved by introducing the surfactantlike Sb atoms during the growth of the InGaAs layer. The improved heterostructural quality and electron transport properties have also been verified by various surface characterization techniques. In comparison, the proposed HEMT with (without) the incorporation of Sb atoms has demonstrated the maximum extrinsic transconductance g(m,max) of 227 (180) mS/mm, a drain saturation current density I-DSS of 218 (170) mA/mm, a gate-voltage swing of 1.215 (1.15) V, a cutoff frequency f(T) of 25 (20.6) GHz, and the maximum oscillation frequency f(max) of 28.3 (25.6) GHz at 300 K with gate dimensions of 1.2 x 200 mu m(2).
Highly stable thermal characteristics of a novel In0.3Ga0.7As0.99N0.01 (Sb)/GaAs high-electron-mobility transistor
(2007-04-01)
Su, Ke-Hua
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Hsu, Wei-Chou
;
Lee, Ching-Sung
;
Hu, Po-Jung
;
Hsia, Ru-Shang
A novel In0.3Ga0.7As0.99N0.01(Sb)/GaAs high-electron-mobility transistor has been successfully investigated for the first time by incorporating surfactant Sb atoms during the InGaAsN channel growth by molecular beam epitaxy (MBE). Superior stable thermal characteristics, including a thermal threshold coefficient (partial derivative V-th/partial derivative T) of -0.807 mV/K and a high-temperature linearity (partial derivative GVS/partial derivative T) of -0.053 mV/K, were achieved because of the improved crystalline quality and the enhanced carrier confinement capability of the In0.3Ga0.7As0.99N0.01(Sb)/GaAs heterostructure. The device also demonstrated a peak extrinsic transconductance (g(m,max)) of 94 (109) mS/mm at 450 (300) K.
Investigations on highly stable thermal characteristics of a dilute In(0.2)Ga(0.8)AsSb/GaAs doped-channel field-effect transistor
(2008-04-01)
Su, Ke-Hua
;
Hsu, Wei-Chou
;
Lee, Ching-Sung
;
Hu, Po-Jung
;
Wu, Yue-Han
This work reports for the first time a novel In(0.2)Ga(0.8)AsSb/GaAs heterostructure doped-channel field-effect transistor (DCFET) grown by the molecular beam epitaxy system. The interfacial quality within the InGaAsSb/GaAs quantum well of the DCFET device has been effectively improved by introducing surfactant-like Sb atoms during the growth of the Si-doped InGaAs channel layer. The improved device characteristics include the peak extrinsic transconductance (g(m, max)) of 161.5 mS mm(-1), the peak drain-source saturation current density (IDSS, max) of 230 mA mm(-1), the gate-voltage swing (GVS) of 1.65 V, the cutoff frequency (f(T)) of 12.5 GHz and the maximum oscillation frequency (f(max)) of 25 GHz at 300 K with the gate dimensions of 1.2 x 200 mu m(2). The proposed design has also shown a stable thermal threshold coefficient (partial derivative V(th)/partial derivative T) of -0.7 mV K(-1).
Liquid Crystal Display (LCD) Supplied by Highly Integrated Dual-Side Dual-Output Switched-Capacitor DC-DC Converter With Only Two Flying Capacitors
(2012-02-01)
Lin, Yang-Ching
;
Luo, Yean-Kuo
;
Chen, Ke-Horng
;
Hsu, Wei-Chou
;
電控工程研究所
This paper proposes a highly integrated dual-side dual-output (DSDO) switched-capacitor (SC) converter with only two flying capacitors. Generally, a dual-phase voltage doubler and an inverter are used to supply positive and negative voltages for thin film transistor-liquid crystal display (TFT-LCD) gate drivers, respectively. Four flying capacitors, eight pin-outs for the four flying capacitors, and 16 power switches are necessary for their operations in the driver integrated chip (IC). The proposed DSDO SC converter combines both dual-phase voltage doubler and inverter converter in one channel through the use of time multiplexing technique with minimal performance degradation. As a result, the proposed converter not only reduces the number of flying capacitors from four to two, but also removes four IC pin-outs for lower cost and more compact size. Moreover, the 16 required power switches are reduced to 12, resulting in an approximated 27% decrease of the silicon area.
Time-Multiplexing Current Balance Interleaved Current-Mode Boost DC-DC Converter for Alleviating the Effects of Right-half-plane Zero
(2012-09-01)
Luo, Yean-Kuo
;
Su, Yi-Ping
;
Huang, Yu-Ping
;
Lee, Yu-Huei
;
Chen, Ke-Horng
In the present study, a time-multiplexing current balance (TMCB) current-mode boost converter is proposed to improve the transient performance. Generally, the crossover frequency of a conventional boost converter is limited to half or less than the right-half-plane (RHP) zero to ensure the system stability. The transient performance of a conventional boost converter is degraded due to its limited bandwidth. The proposed TMCB boost converter extends its bandwidth and moves the RHP zero to a higher frequency to improve the transient performance using two inductors in one channel. Besides, the small signal model of dual phase system which considers cross-couple effect and offset correction is presented. The proposed converter requires an extra inductor and a slight increase in the size of the printed circuit board layout and die size. Using time multiplexing, two inductors were operated in an interleaved phase at a switching frequency of 5 MHz rather than a single inductor system operated at a switching of 10 MHz for the same ripple required. Experimental results show that the TMCB technique is effective in correcting the mismatch in the current of the inductors even if the difference between the inductors is large. Furthermore, the proposed converter can improve the settling time from 52 to 22 mu s due to an extended bandwidth.
Transient Improvement by Window Transient Enhancement and Overshoot Suppression Techniques in Current Mode Boost Converter
(2011-10-01)
Luo, Yean-Kuo
;
Chiou, Chao-Chang
;
Wu, Chun-Hsien
;
Chen, Ke-Horng
;
Hsu, Wei-Chou
In this paper, a current mode boost converter using window transient enhancement (WTE) and overshoot suppression (OSS) technique is presented for digital still camera (DSC) applications. The peak-to-peak transient overshoot voltage demand of a DSC motor driver is generally within 4%-5% of the regulated value. However, conventional boost converters usually fail to pass this criterion during large load transient. The OSS technique reduces the overshoot voltage when load current changes from heavy to very light. Experimental results show that compared with the use of a conventional current mode boost converter, the use of the technique reduces drop voltage about 62% and overshoot voltage about 51% when the load current has a load step of 400 mA. Moreover, the settling time improves to 43%, which is better than in the conventional case of a 400 mA load current step. The overhead of the silicon area is about 4.5% to achieve the overshoot reduction. The estimated high performance demonstrates that it is suitable for DSC applications.