• 센서학회지
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• 제18권1호
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• pp.95-101
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• 2009

A simple and new CMOS potentiostat circuit for amperometric sensor is described. To maintain a constant potential between the reference and working electrodes, only one differential difference amplifier (DDA) is needed in proposed design, while conventional potentiosatat requires at least 2 operational amplifiers and 2 resistors, or more than 3 operational amplifiers and 4 resistors for low voltage CMOS integrated potentiostat. The DDA with rail-to-rail design not only enables the full range operation to supply voltage but also provides simple potentiostat system with small hardwares and low power consumption.

• 전기학회논문지
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• 제67권12호
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• pp.1641-1647
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• 2018

In this paper, we describe a portable potentiostat which is capable of cyclic voltammetry(CV) and amperometry for electrochemical dissolved oxygen sensor. In addition, this portable potentiostat can also transmit the measured data wirelessly to android devices such as smart phone, tablet, etc. through Bluetooth. The potentiostat system consists of three parts; a voltage generator circuit which is controlled by Arduino nano and 12-bit DAC(digital to analog converter) to generate necessary electric potential for operating the electrochemical sensor, an oxidation/reduction current measurement circuit, and a Bluetooth module to transmit data wirelessly to an android device. Once measurements are carried out with the android application, the measured data is transmitted to the android device via Bluetooth and displayed using the android app. in real time. In this paper, we report the measured reduction current with a fabricated dissolved oxygen sensor in both saturated-oxygen state and zero-oxygen states. The results of the developed portable potentiostat system are in good agreement with those of the commercial portable potentiostat (${\mu}stat200$, Dropsens inc.). The measured peak reduction currents using the developed potentiostat and the commercial ${\mu}stat200$ potentiostat were $-0.755{\mu}A$ and $-0.724{\mu}A$, respectively. The reduction currents measured at zero-oxygen state were $-0.005{\mu}A$ and $-0.004{\mu}A$. The discrepancy between those two systems seems very small, which implies successful development of a portable and wireless potentionstat.

• 센서학회지
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• 제3권3호
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• pp.22-27
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• 1994

마이크로 산소분압센서의 특성에 맞는, CMOS op-amp로 구성된 potentiostat 및 I-V converter용 op-amp를 설계하였다. 시뮬레이션 결과, 설계된 potentiostat는 $l.1k{\Omega}$의 낮은 출력저항을 나타냈으며, 산소분압센서의 등가회로와 연결한 경우 $-3{\sim}2.5V$범위의 전압을 선형적으로 인가할 수 있었고 안정한 주파수 특성을 보였다. 또한 I-V converter의 입력 저항은 약 $30{\Omega}$으로 작았으며 좋은 직선성을 나타내었다.

• 전기학회논문지
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• 제65권4호
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• pp.622-627
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• 2016

This paper describes the development of a portable potentiostat which can perform square wave voltammetry on electrochemical sensors and wireless transmission of the measured data to a smartphone using Bluetooth. The potentiostat consists of a square wave potential pulse generation circuit for applying the potential pulse to the electrochemical sensor, a reduction/oxidation (or redox) current measurement circuit, and Bluetooth for wireless data transmission to an Android-based smartphone. The measured data are then processed to show the output graph on the smart phone screen in real time. This data transformation into a graph is carried out by developing and installing a simple transformation application software in the Android-based smartphone. This application software also enables the user to set and change the measurement parameters such as the applied voltage range and measured current range at user's convenience. The square voltammetry output data measured with the developed portable potentiostat were almost same as the data of the commercial potentiostat. The measured oxidation peak current with the commercial potentiostat was $11.35{\mu}A$ at 0.26 V and the measured oxidation peak current with the developed system was $12.38{\mu}A$ at 0.25 V. This proves that performance of the developed portable measurement system is comparable to the commercial one.

• Transactions on Electrical and Electronic Materials
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• 제14권5호
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• pp.273-277
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• 2013

A unified potentiostat circuit for both $O_2$- and $H_2O_2$- based electrochemical glucose sensors was proposed and its function was verified by circuit simulations and measurement results of a fabricated chip. This circuit consisted of an operational amplifier, a comparator and current mirrors. The proposed circuit was fabricated with a $0.13{\mu}m$ thick oxide CMOS process and an active area of $360{\mu}m{\times}100{\mu}m$. The measurements revealed an input operation range from 0.5 V to 1.6 V in the $H_2O_2$- based bio-sensor and from 1.7 V to 2.6 V in the $O_2$- based bio-sensor with a supply voltage of 3.3 V. The evaluation results showed that the proposed potentiostat circuit is suitable for measuring the electrochemical cell currents of both $O_2$- and $H_2O_2$- based glucose sensors.

• 한국정보통신학회논문지
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• 제21권2호
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• pp.345-352
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• 2017

본 논문에서는 전원전압 1V에서 동작하는 산소 및 과산화수소 기반의 혈당전류를 측정할 수 있는 통합형 정전압분극장치를 설계하고 제작하였다. 정전압분극장치는 저전압 OTA, 캐스코드 전류거울 그리고 모드 선택회로로 구성되어 있다. 정전압분극장치는 산소 및 과산화수소 기반에서 혈당의 화학반응으로 발생하는 전류를 측정할 수 있다. OTA의 PMOS 차동 입력단의 바디에는 순방향전압을 인가하여 문턱전압을 낮추어 낮은 전원전압이 가능하도록 하였다. 또한 채널길이변조효과로 인한 전류의 오차를 줄이기 위해 캐스코드 전류거울이 사용되었다. 제안한 저전압 정전압분극장치는 Cadence SPECTRE를 이용하여 설계하였으며, 매그나칩 $0.18{\mu}m$ CMOS 공정을 이용하여 제작되었으며 회로의 크기는 $110{\mu}m{\times}60{\mu}m$이다. 전원전압 1.0V에서 소모전류는 최대 $46{\mu}A$이다. 페리시안화칼륨($K_3Fe(CN)_6$)을 사용하여 제작된 정전압분극장치의 성능을 확인하였다.

• Restorative Dentistry and Endodontics
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• 제19권2호
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• pp.534-548
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• 1994

The purpose of this study is to observe the corrosion characteristics of seven dental amalgams (CAULK FINE CUT, CAULK SPHERICAL, OPTALLOY II, DISPERSALLOY, HI VERALOY, TYTIN, VALIANT) through the anodic polarization curve obtained by using a potentiostat. After each amalgam alloy and Hg being triturated, the triturated mass was inserted into the cylindrical metal mold, and condensed by hydrolic pressure(160 kg/$cm^2$). Each specimen was removed from the metal mold. 24 hours after condensation, specimens were polished with the emery paper and stored at room temperature for 1 week. The anodic polarization curves were employed to compare the corrosion behaviours of the amalgam in 0.9% saline solution, Fusayama's artificial saliva, and stimulated parotid saliva at $37^{\circ}C$ with 3-electrode potentiostat. After the immersion of specimen in electrolyte for 1 hour, the potential scan was begun. The potential scan range was. -1700m V ~ + 400m V(vs. S. C. E) in the working electrode and the scan rate was 50m V /sec. The results were as follows, 1. The corrosion potential, the potential of anodic current peak, and transpassive potential in the stimulated parotid saliva shifted to more anodic direction than those in saline solution, and the current density in the stimulated parotid saliva was lower than that in saline solution. Those in Fusayama's artificial saliva was similar to those in stimulated parotid saliva. 2. The anodic polarization profiles in Fusayama's artificial saliva and stimulated parotid saliva indicated a region of slow slope current density, which is extending from the corrosion potential to the potential of anodic current peak, but that in 0.9% saline solution indicated no region of slow slope. 3. The corrosion potentials for CAULK FINE CUT, CAULK SPHERICAL, and OPT ALLOY II had the similarity in 0.9% saline solution, Fusayama's artificial saliva and stimulated parotid saliva, but those for high coper amalgam and VALIANT had no similarity. 4. The current density for TYTIN amalgam in stimulated parotid saliva was the lowest among the others. 5. As for current density, there was no significant difference between palladium enriched VALINAT and other high copper amalgams.

• 마이크로전자및패키징학회지
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• 제24권4호
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• pp.59-63
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• 2017

n-type GaN 반도체는 광전극으로서 우수한 성질을 가지고 있지만, 표면에서 일어나는 산소반응으로 인한 광부식으로 신뢰성이 저하되는 큰 단점이 있다. 이를 근본적으로 억제하기 위하여 표면에서 수소 발생 반응이 일어나는 p-type GaN를 광전극으로 사용함으로써 광부식을 피하고자 하는 연구가 진행되고 있다. 하지만 p-type GaN은 비저항이 높고 정공 이동도가 낮기 때문에 효율이 낮다는 단점을 가지고 있다. 본 연구에서는 이러한 문제를 p-type GaN의 activation 공정을 통해 개선하고자 한다. 전극으로 사용될 p-type GaN을 $N_2$ 분위기의 $500^{\circ}C$에서 1 분 동안 annealing을 하였다. Hall effect 측정을 통하여 전기적 특성을 확인하였으며, potentiostat (PARSTAT4000) 측정을 통하여 광전기화학적 (photoelectrochemical, PEC) 특성을 분석하였다. 그 결과 annealing 공정을 통하여 광전류밀도가 1.5배 이상 향상되었으며, 3시간 동안 안정적인 광전류 값을 확인하였다.

• Restorative Dentistry and Endodontics
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• 제22권1호
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• pp.396-412
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• 1997

The purpose of this study is to observe the corrosion characteristics of five dental amalgams(CAULK FINE CUT, OPTALLOY II, DISPERSALLOY, TYTIN, and VALIANT) in the solutions with fluoride compound through the anodic polarization curve obtained by using a potentiostat. After each amalgam alloy and Hg being triturated, the triturated mass was inserted into the cylindrical metal mold, and condensed by hydraulic pressure(160 kg/$cm^2$). Each specimen was removed from the metal mold. Specimens were polished with the silicone carbide grinding paper 24 hours after condensation and stored at room temperature for 1 week. The anodic polarization curves were employed to compare the corrosion behaviours of the amalgams in 0.9 % saline solution and in the saline solutions with 2.2 ppm, 0.05 %, 2 % NaF, and 8 % $SnF_2$ at $37^{\circ}C$ with 3-electrode potentiostat. After the immersion of specimen in electrolyte for 30 minutes, the potential scan was begun. The potential scan range was -1500m V to + 800m V(vs. S.C.E.) in the working electrode and the scan rate was 50 mV/sec. The results were as follows, 1. The corrosion potential, the potential of anodic current peak, and transpassive potential in the saline solutions with NaF shifted to lower direction than those in normal saline solution, and the current density in the saline solutions with NaF was higher than that in normal saline solution. The differences were increased as the concentrations of NaF became higher. 2. The corrosion potential and transpassive potential in the saline solution with $SnF_2$ shifted to higher direction than those in normal saline solution, and the current density in the saline solution with $SnF_2$ was higher than that in normal saline solution after the corrosion potential. The anodic polarization curves in the saline solution with $SnF_2$ had no outstanding anodic current peak. 3. The corrosion potentials for high-copper amalgams were much higher than those for CAULK FINE CUT and OPTALLOY II in normal saline solution, but, as the concentrations of fluoride compound became higher, the differences in corrosion potentials between them were decreased. The corrosion potentials had the similarity in the saline solution with 2% NaF or 8% $SnF_2$. 4. The current density for TYTIN was the lowest among the others in normal saline solution and in the saline solution with 2.2 ppm or 0.05 % NaF. 5. There was no significant difference in current density between Pd-enriched VALIANT and other high-copper amalgams.

• 한국표면공학회지
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• 제37권2호
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• pp.119-127
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• 2004

In order to develop the corrosion and wear resistance of stainless steels, effects of plasma-nitriding on the surface characteristics of stainless steels containing Nb were investigated by utilizing a potentiostat. It was found that plasma nitriding at $350^{\circ}C$, compared with $500^{\circ}C$, produced a good corrosion resistance as nitriding time increased, whereas stainless steel containing low Nb content showed that pitting potential and corrosion potential decreased.