• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제50권3호
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• pp.144-148
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• 2001

For the purpose of developing capacitive humidity sensor having interdigit electrodes, interdigit electrode was modeled and simulated to obtain capacitance and sensitivity as a function of geometric parameters like the structural gap and thichness. For the development of ASIC, switched capacitor signal conditioning circuits for capacitive humidity sensor were designed and simulated by cadence using 0.25um CMOS process parameters. The signal conditioning circuits are composed of amplifier for voltage gain control, and clock generator for sensor driving and switch control The characteristics of the fabricated sensors are; 1) sensitivity is 9fF/%R.H., 2) temperature coefficient of offset(TCO) is 0.4%R.H./$^{\circ}C$, 3) nonlinearity is 1.2%FS, 4) hysteresis is 1.5%FS in humidity range of 3%R.H. ${\sim}$ 98%R.H.. The response time is 50 seconds in adsorption and 70 seconds in desorption. Fabricated process used in this capacitive humidity sensor having interdigit electrode are just as similar as conventional IC process technology. Therefore this can be easily mass produced with low cost, simple circuit and utilized in many applications for both industrial and environmental measurement and control system, such as monitoring system of environment, automobile, displayer, IC process room, and laboratory etc..

• Journal of Magnetics
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• 제15권4호
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• pp.194-198
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• 2010

In our present work, we developed a GMI (giant magnetoimpedance) sensor system to detect magnetic fields in the milli gauss range based on the asymmetric magnetoimpedance (AGMI) effect in Co-based amorphous ribbon with self bias field produced by field-annealing in open air. The system comprises magnetoimpedance sensor probe, signal conditioning circuits, A/D converter, USB controller, notebook computer, and program for measurement and display. Sensor probe was constructed by wire-bonding the cobalt based amorphous ribbon with dimensions $10\;mm\;{\times}\;1\;mm\;{\times}\;20\;{\mu}m$ on a printed circuit board. Negative feedback was used to remove the hysteresis and temperature dependence and to increase the linearity of the system. Sensitivity of the milli gauss meter was 0.3 V/Oe and the magnetic field resolution and environmental noise level were less than 0.01 Oe and 2 mOe, respectively, in an unshielded room.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1997년도 추계학술대회 논문집
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• pp.21-24
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• 1997

Ferroeletric LiNbO$_3$ thin films hale been prepared directly on Si(100) substrates by conventional RF magnetron spurttering system for nonvolatile memory applications. As-deposited films were performed RTA(Rapid Thermal Annealing) treatment in an oxygen atmosphere at 600 $^{\circ}C$ for 60 s. The rapid thermal annealed films were changed to poly-crystalline ferroelectric nature from amorphous of as-deposition. The resistivity of the ferroelectric LiNbO$_3$ film was increased from a typical vague of 1~2$\times$10$^{8}$ $\Omega$.cm before the annealing to about 1$\times$10$^{13}$ $\Omega$.cm at 500 kV/cm and reduce the interface state density of the LiNbO$_3$/Si(100) interface to about 1$\times$10$^{11}$ cm$^2$ . eV. Ferroelectric hysteresis measurements using a Sawyer-Tower circuit yielded remanent polarization (Pr) and coercive field (Ec) values of about 1.2 $\mu$C/cm$^2$ and 120 kV/cm, respectively.

• 전기전자학회논문지
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• 제14권2호
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• pp.51-57
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• 2010

대형 TFT LCD 판넬의 감마보정전압을 구동하기 위한 레일-투-레일 고전압 CMOS 완충 증폭기를 제안하였다. 이 회로는 단일 전압하에서 동작하고 18V 전압원에서 0.5mA 의 전류소비특성을 나타내며 8비트/10비트 고해상도 TFT LCD 판넬의 감마보정 전압 구동을 위하여 설계하였다. 이 회로는 높은 slew rate, 0.5mA의 정적 전류특성을 나타내며 1k$\Omega$의 저항성/용량성 부하구동 능력을 가지고 있다. 또한 넓은 출력 공급범위를 지니며, 5mA의 출력 정전류를 내보낼 경우 50mV미만의 옵셋전압 특성을 가진다. 또한, 용량성 부하 구동시 입력기준 옵셋전압이 2.5mV 미만인 좋은 특성을 나타낸다. 본 논문에서는 넓은 스윙입력범위와 출력 동작 범위을 얻기 위해 전류미러형 n-채널 차동증폭기, p-채널 차동증폭기, AB-급 푸쉬-풀 출력단, 히스테리시스 비교기를 사용한 입력레벨 검출기 등을 사용하였다. 제안된 회로는 고전압 디스플레이 구동 IC에 사용하기 위해 0.18um 18V 고전압 CMOS 공정기술에 의해 제작되었다. 제안된 회로는 8~18V의 공급 전압 범위에서 동작한다.

• 한국산학기술학회논문지
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• 제17권6호
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• pp.715-720
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• 2016

본 논문에서는, 휴대기기를 위한 PWM(Pulse Width Modulation), 전압모드 DC-DC 승압형 컨버터를 제안한다. 제안하는 컨버터는 현재 소형화 되어가고 있는 휴대기기 시장에 적합하도록 1 MHz의 스위칭 주파수를 사용하여 칩 면적을 줄였다. 제안하는 DC-DC 컨버터는 전력단과 제어단으로 이루어지며 전력단은 인덕터, 출력 커패시터, MOS 트랜지스터 등으로 구성되며 제어단은 연산증폭기, 밴드갭 회로, 소프트 스타트 블록, 히스테리시스 비교기와 비겹침 드라이버로 구성된다. 설계된 회로는 히스테리시스 비교기와 논오버랩 드라이버를 사용하여 낮은 전압에서 구동되는 휴대기기의 잡음의 영향을 줄이고 출력전압 리플을 감소시켰다. 제안하는 회로는 1-poly 6-metal CMOS 매그나칩/하이닉스 $0.18{\mu}m$ 공정을 사용하여 레이아웃을 진행하였다. 설계된 컨버터는 입력 전압 3.3 V, 출력전압 5 V, 출력전류 100 mA 출력전압 대비 1%의 출력 전압 리플과 1 MHz의 스위칭 주파수의 특성을 갖는다. 본 논문에서 제안하는 승압형 DC-DC 컨버터는 PDA, 휴대폰, 노트북 등 휴대용 전자기기 시장에 맞는 고효율, 소형화 컨버터로서 유용하게 사용 될 것으로 사료된다.

• 대한의용생체공학회:의공학회지
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• 제37권5호
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• pp.168-177
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• 2016

In this paper we present an implantable pressure sensor to measure real-time blood pressure by monitoring mechanical movement of artery. Sensor is composed of inductors (L) and capacitors (C) which are formed by microfabrication and direct bonding on two biocompatible substrates (quartz). When electrical potential is applied to the sensor, the inductors and capacitors generates a LC resonance circuit and produce characteristic resonant frequencies. Real-time variation of the resonant frequency is monitored by an external measurement system using inductive coupling. Structural and electrical simulation was performed by Computer Aided Engineering (CAE) programs, ANSYS and HFSS, to optimize geometry of sensor. Ultrafast laser (femto-second) cutting and MEMS process were executed as sensor fabrication methods with consideration of brittleness of the substrate and small radial artery size. After whole fabrication processes, we got sensors of $3mm{\times}15mm{\times}0.5mm$. Resonant frequency of the sensor was around 90 MHz at atmosphere (760 mmHg), and the sensor has good linearity without any hysteresis. Longterm (5 years) stability of the sensor was verified by thermal acceleration testing with Arrhenius model. Moreover, in-vitro cytotoxicity test was done to show biocompatiblity of the sensor and validation of real-time blood pressure measurement was verified with animal test by implant of the sensor. By integration with development of external interrogation system, the proposed sensor system will be a promising method to measure real-time blood pressure.

• 전자공학회논문지A
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• 제32A권7호
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• pp.77-84
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• 1995

We studied the effects of the Zr/Ti ration and the bottom electrode (Pt or ITO) on the electrical properties of PZT thin films prepared by sol-gel method. Their permittivities and tagent losses with the variation of frequencies were measured by the LCR meter and their maximum polarizations, remanent polarizations, and coercive fields were obtained from the hysteresis loops measured by the Sawyer-Tower circuit. For the PZT thin film of the Zr/Ti ration of 53/47, permittivity at 10kHz, coercive field, maximum and remanent polarizations ere measured as 952, 20.7kV/cm, 10.43${\mu}C/cm^{2}$ and 4.3${\mu}C/cm^{2}$, respectively. For the film of the Zr/Ti ration of 25/75, coercive field, maximum and remanent polarizations were measured as 33.12kV/cm, 5.59${\mu}C/cm^{2}$ and 1.5${\mu}C/cm^{2}$, respectively. For the film of the Zr/Ti ratio of 75/25, they were measured as 23.8kV/cm, 7.45${\mu}C/cm^{2}$, and 3.5${\mu}C/cm^{2}$, repectively. Our investigation into the effects of the lower electrode on the electrical properties of PZT films showed the following results. The permittivities of the PZT films deposited on the ITO electrode decreased more quickly than those of the PZT films on the Pt electrode. The tangent losses of the former films increased more quickly than those of the latter. These may be due to the degradation of the quality of the interface between the electrode and the film, which results from the diffusion of Pb. It is also noticeable that permittivities and tangent losses of the PZT films deposited on the ITO electrode varied differently with the Zr/Ti ratio. This may indicate that the quality of the interface between the electrode and the film changes with the Zr/Ti ration of the PZT film.

• E2M - 전기 전자와 첨단 소재
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• 제10권2호
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• pp.134-140
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• 1997

PbTiO$_{3}$-PbZrO$_{3}$-Pb(Ni$_{1}$3/Nb $_{2}$3/O$_{3}$)(PZT-PNN) thin films were prepared from corresponding metal organics partially stabilized with diethanolamine by the sol-gel spin coating method. Each mol rates of PT:PZ:PNN solutions were #1(50:40:10), #2(50:30:20), #3(45:35:20) and #4(40:40:20), respectively. The spin-coated PZT-PNN films were sintered at the temperature from 500.deg. C to 600.deg. C for crystallization. The P-E hysteresis curve was drawn by Sawyer-Tower circuit with PZT-PNN film. The coercive field and the remanent polarization of #4(40:40:20 mol%) PZT-PNN film were 28.8 kV/cm and 18.3 .mu.C/cm$^{2}$, respectively. Their dielectric constants were shown between 128 and 1120, and became maximum value in MPB(40:40:20 mol%). The leakage currents of PZT-PNN films were about 9.4x 10$^{-8}$ A/cm$^{2}$, and the breakdown voltages were about 0.14 and 1.1 MV/cm. The Curie point of #3(45:35:20 mol%, sintered at 600.deg. C) film was 330.deg. C.

• 한국산학기술학회논문지
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• 제16권8호
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• pp.5541-5549
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• 2015

본 논문은 반도체 웨이퍼 공정 배기가스 수분제어장치에 적용하기 위하여 인덕션 히터를 사용해서 안전하고 효율적인 전력을 사용하는 히터에 대한 설계방법을 제안한다. 수분을 제거하기 위해서 질소 가스의 흡열 반응을 발생하는 필라멘트 히터를 이용하여 배기가스 제거 시스템이 만들어진다. 이론적인 최적화와 전기적인 구현을 통해서 인덕션 이론은 반도체 웨이퍼 공정 배기가스 시스템을 위한 인덕션 히터 설계과정에 적용되어진다. 제안한 인덕션 히터 설계는 에너지 측면에서 비효율적이고 신뢰성이 떨어지며 안전하지 못한 현재의 설계문제에 대한 해결책을 제시한다. 인덕션 히터의 강인성과 미세조정 설계기법이 질소 히터의 사양내에서 에너지 소모를 최적화한다. 최적화는 배기 파이프의 공진주파수에 의해서 특성화된 ZVS(Zero Voltage Switching)를 기초로 이루어진다. 시스템에서 끼어진 고장 안전(fail-safe) 에너지 리미터는 MOSFET의 궤환 제어를 통하여 전압 레귤레이터를 사용하고 N2 히터 유닛의 사양이내에서 작동하기 위한 성능을 만족하도록 한다. 수치 해석과 설계의 우수성을 위한 기존의 필라멘트 히터와 미세조정한 인덕션 히터 설계의 사양과 성능비교는 제안한 인덕션 히터 설계방법이 우수함을 보여준다.