• Title/Summary/Keyword: Negative Capacitance

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A PLL with loop filter consisted of switch and capacitance (커패시턴스와 스위치로 구성된 루프필터를 가진 PLL)

  • Ahn, Sung-Jin;Choi, Young-Shig
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • 2016.05a
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    • pp.154-156
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    • 2016
  • In this paper, the proposed small size PLL works stable with the discrete loop filter which is controlled by voltage controlled oscillator's output signal. Sampling and a small size capacitor functioned negative feedback with switch does make it possible to integrate the PLL into a single chip. The proposed PLL is designed by 1.8V 0.18um CMOS process.

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An OTA with Positive Feedback Bias Control for Power Adaptation Proportional to Analog Workloads

  • Kim, Byungsub;Sim, Jae-Yoon;Park, Hong-June
    • JSTS:Journal of Semiconductor Technology and Science
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    • v.15 no.3
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    • pp.326-333
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    • 2015
  • This paper reports an adaptive positive feedback bias control technique for operational transconductance amplifiers to adjust the bias current based on the output current monitored by a current replica circuit. This technique enables operational transconductance amplifiers to quickly adapt their power consumption to various analog workloads when they are configured with negative feedback. To prove the concept, a test voltage follower is fabricated in $0.5-{\mu}m$ CMOS technology. Measurement result shows that the power consumption of the test voltage follower is approximately linearly proportional to the load capacitance, the signal frequency, and the signal amplitude for sinusoidal inputs as well as square pulses.

Dielectric Constant with $SiO_2$ thickness in Polycrystalline Si/ $SiO_2$II Si structure (다결정 Si/ $SiO_2$II Si 적층구조에서 $SiO_2$∥ 층의 두께에 따른 유전특성의 변화)

  • 송오성;이영민;이진우
    • Journal of the Korean institute of surface engineering
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    • v.33 no.4
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    • pp.217-221
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    • 2000
  • The gate oxide thickness is becoming thinner and thinner in order to speed up the semiconductor CMOS devices. We have investigated very thin$ SiO_2$ gate oxide layers and found anomaly between the thickness determined with capacitance measurement and these obtained with cross-sectional high resolution transmission electron microscopy. The thicknesses difference of the two becomes important for the thickness of the oxide below 5nm. We propose that the variation of dielectric constant in thin oxide films cause the anomaly. We modeled the behavior as (equation omitted) and determined $\varepsilon_{bulk}$=3.9 and $\varepsilon_{int}$=-4.0. We predict that optimum $SiO_2$ gate oxide thickness may be $20\AA$ due to negative contribution of the interface dielectric constant. These new results have very important implication for designing the CMOS devices.s.

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Deposition $Ba_{1-x}Sr_xTiO_3$Thin Films and Electrical Properties with Various Materials Top Electrodes (강유전체$Ba_{1-x}Sr_xTiO_3$ 박막의 제조 및 상부전극재료에 따른 전기적 특성)

  • Park, Choon-Bae;Kim, Deok-Kyu;Jeon, Jang-Bae
    • The Transactions of the Korean Institute of Electrical Engineers C
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    • v.48 no.6
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    • pp.410-415
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    • 1999
  • $Ba_{1-x}Sr_xTiO_3$ thin films with various ratio of Sr (X = 0.4, 0.5, 0.6) were grown $Pt/TiN/SiO_2/Si$ subastrate by RF magnetron sputtering deposition. As, Ag, and Cu films were deposited on $Ba_{1-x}Sr_xTiO_3$ thin films as top electrodes by using a thermal evaporator. The electrical properties of $Ba_{1-x}Sr_xTiO_3$ thin films for various compositions were characterized and the physical properties at interface between $Ba_{1-x}Sr_xTiO_3$ thin films and top electrodes were evaluated in terms of the work function difference. At x =0.5, the degradation of capacitance is lower to the other compositions. As negative biasapplied, the specimen with Cu top electrode has board saturation region and low leakage current since work function of Cu is bigger than other electrodes.$ Ba_{0.5}Sr_{0.5}TiO_3$ thin films with Cu top electrode, the dielectric constant was measured to the value of 354 at 1 kHz and the leakage current was obtained to the value of $5.26\times10^{-6}A/cm2$ at the forward bias of 2 V.

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PEDOT:PSS Enhanced Electrochemical Capacitive Performance of Graphene-Templated δ-MnO2

  • Sinan, Neriman;Unur, Ece
    • Journal of Electrochemical Science and Technology
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    • v.11 no.1
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    • pp.50-59
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    • 2020
  • Birnessite-type manganese dioxide (δ-MnO2) with hierarchical micro-/mesoporosity was synthesized via sacrificial graphene template approach under mild hydrothermal conditions for the first time. Graphene template was obtained by a surfactant (cetyltrimethylammonium bromide, CTAB) assisted liquid phase exfoliation (LPE) in water. A thin PEDOT:PSS (poly (3,4-ethylene dioxythiophene): poly (styrene sulfonate)) layer was applied to improve electrical conductivity and rate capability of MnO2. The MnO2 (535 F g-1 at 1 A g-1 and 45 F g-1 at 10 A g-1) and MnO2/PEDOT:PSS nanocomposite (550 F g-1 at 1 A g-1 and 141 F g-1 at 10 A g-1) delivered electrochemical performances superior to their previously reported counterparts. An asymmetric supercapacitor, composed of MnO2/PEDOT:PSS (positive) and Fe3O4/Carbon (negative) electrodes, provided a maximum specific energy of 18 Wh kg-1 and a maximum specific power of 4.5 kW kg-1 (ΔV= 2 V, 1M Na2SO4) with 85% capacitance retention after 1000 cycles. The graphene-templated MnO2/PEDOT:PSS nanocomposite obtained by a simple and green approach promises for future energy storage applications with its remarkable capacitance, rate performance and cycling stability

Asymmetric Supercapacitors Based on Co3O4@MnO2@PPy Porous Pattern Core-Shell Structure Cathode Materials

  • Wang, Zihan;Pan, Shuang;Wang, Bing;Qi, Jingang;Tang, Lidan;Liu, Liang
    • Journal of Electrochemical Science and Technology
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    • v.12 no.3
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    • pp.346-357
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    • 2021
  • In recent years, supercapacitors have been developed rapidly as a rechargeable energy storage device. And the performance of supercapacitors is depending on electrode materials, the preparation method and performance of electrode materials have become the primary goal of scientific development. This study synthesizes Co3O4@MnO2@PPy cathode material with porous pattern core-shell structure by hydrothermal method and electrodeposition. The result samples are characterized by X-ray diffraction transmission/scanning electron microscope, and X-ray photoelectron spectroscopy. Electrochemical evaluation reveals that electrochemical performance is significantly enhanced by PPy depositing. The specific capacitance of Co3O4@MnO2@PPy is 977 F g-1 at 1 A g-1, the capacitance retention rate of 105%. Furthermore, the electrochemical performance of Co3O4@MnO2@PPy//AC asymmetric supercapacitor assembles with AC as the negative electrode material is significantly better than that of MnO2//AC and Co3O4@MnO2//AC. The capacity of Co3O4@MnO2@PPy//AC is 102.78 F g-1. The capacity retention rate is still 120% for 5000 charge-discharge cycles.

Analysis on the Noise Factors of Static Induction Photo-Transistor (SIPT) (1) - The SIPT's Equivalent Circuits for the Analysis on the Noise Factors - (정전유도(靜電誘導) 포토 트랜지스터의 잡음(雜音) 원인(原因) 분석(分析) (1) - 잡음(雜音) 원인(原因) 분석(分析)을 위한 SIPT 등가회로(等價回路) -)

  • Kim, Jong-Hwa
    • Journal of Sensor Science and Technology
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    • v.4 no.4
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    • pp.29-40
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    • 1995
  • In this paper, the noise equivalent cicuits that is necessary to the formulation of D.C. and noise characteristics, residual component and input capacitance so as to analyze on the noise factors of the SIT is proposed. The simplest noise equivalent circuit is the model representing the mechanism of the SIT and the measured values in this model were found as small as the values of the shot-noise. In the source resistance inserted equivalent circuit is conformed that the shot-noise will be reduced by the negative-feedback effect of the source resistance. In oder to analyze the correct noise reduction factor, I proposed the equivalent circuit which the formulas of the source and drain resistance was induced. In the experiment which affirm the equivalent circuits, the influence of the signal source resistance and output load resistance on the residual component is small and the residual component can be expressed by the equivalent input noise resistance. Moreover, the input capacitance is 13.6 pF when the load resistance is $0{\Omega}$ and the capacitance which does not concern with the SIT operation directly, that is, gate wire etc, is 10pF or so.

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Preparation of Heated Tobacco Biomass-derived Carbon Material for Supercapacitor Application (궐련형 담배 바이오매스 기반의 슈퍼커패시터용 탄소의 제조 및 응용)

  • Kim, Jiwon;Jekal, Suk;Kim, Dong Hyun;Yoon, Chang-Min
    • Journal of the Korea Organic Resources Recycling Association
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    • v.30 no.2
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    • pp.5-15
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    • 2022
  • In this study, heated tobacco biomass was prepared as an active material for supercapacitor device. Retrieved tobacco leaf from the heated tobacco was carbonized at various temperature(800/850/950℃). Carbonized tobacco leaf material synthesized at 850℃ exhibited the highest C/O ratio, indicating the finest carbon quality. In addition, polypyrrole was coated onto the carbonized leaf material for increasing the electrochemical performance via low-temperature polymerization method. As-synthesized carbonized leaf material at 850℃(CTL-850)-based electrode and polypyrrole-coated carbonized leaf material(CTL-850/PPy)-based electrode displayed outstanding specific capacitances of 100.2 and 155.3F g-1 at 1 A g-1 with opertaing window of -1.0V and 1.0V. Asymmetric supercapacitor device, assembled with CTL-850 as the negative electrode and CTL-850/PPy as the positive electrode, manifested specific capacitance of 31.1F g-1(@1 A g-1) with widened operating voltage window of 2.0V. Moreover, as-prepared asymmetric supercapacitor device was able to lighten up the RED Led (1.8V), suggesting the high capacitance and extension of operating voltage window. The result of this research may help to pave the new possibility toward preparing the effective energy storage device material recycling the biomass.

Growth and Electrical Characteristics of Ultrathin $SiO_2$ Film Formed in an Electron Cyclotron Resonance Oxygen Plasma (ECR 산소 플라즈마에 의한 $SiO_2$ 박막의 성장 거동 및 전기적 특성)

  • 안성덕;이원종
    • Journal of the Korean Ceramic Society
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    • v.32 no.3
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    • pp.371-377
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    • 1995
  • Silicon oxide films were grown on single-crystal silicon substrates at low temperatures (25~205$^{\circ}C$) in a low pressure electron cyclotron resonance (ECR) oxygen plasma. The growth rate of the silicon oxide film increased as the temperature increased or the pressure decreased. Also, the thickness of the silicon oxide film increased at negative bias voltage, but not changed at positive bias voltage. The growth law of the silicon oxide film was approximated to the parabolic form. Capacitance-voltage (C-V) and current density-electric field (J-E) characteristics were studied using Al/SiO2/p-Si MOS structures. For a 10.2 nm thick silicon oxide film, the leakage current density at the electric field of 1 MVcm-1 was less than 1.0$\times$10-8Acm-2 and the breakdown field was higher than 10 MVcm-1. The flat band voltage of Al/SiO2/p-Si MOS capacitor was varied in the range of -2~-3 V and the effective dielectric constant was 3.85. These results indicate that high quality oxide films with properties that are similar to those of thermal oxide film can be fastly grown at low temperature using the ECR oxygen plasma.

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Design and Implementation of X-Band Oscillator Using Compact Hairpin Resonator (소형화된 헤어핀 공진기를 이용한 X-대역 발진기의 설계 및 구현)

  • Kim, Gi-Rae
    • The Journal of the Korea institute of electronic communication sciences
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    • v.9 no.10
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    • pp.1131-1137
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    • 2014
  • In this paper, oscillator with compact hairpin resonator is used to design the local oscillator of X-band radar system. The proposed hairpin resonator is minimized by increasing capacitance of line end of conventional one. By this method, size can be minimized about 40% compared with the conventional resonator and also can improve phase noise characteristic. The result of oscillator using proposed hairpin resonator is measured in oscillating frequency of 9.05 GHz, output power of 2.47 dBm, and phase noise of -101.4 dBc/Hz. The fabricated oscillator in this paper can minimize design and it's planar structure makes it easy to design MMIC.