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14 비트 분해능을 갖는 2차 Sigma-Delta 변조기 설계를 위한 구성요소의 최대에러 허용 범위 조사
조병욱,최평,손병기,Cho, Byung-Woog,Choi, Pyung,Sohn, Byung-Ki 한국통신학회 1998 한국통신학회논문지 Vol.23 No.5
Sigma-delta converter is frequently used for conyerting low-frequency anglog to digital signal. The converter consists of a modulator and a digital filer, but our work is concentrated on the modulator. In this works, to design second-order sigma-dalta modulator with 14bit resolution, we define maximumerror limits of each components (operational smplifier, integrator, internal ADC, and DAC) of modulator. It is first performed modeling of an ideal second-order sigma-delta modulator. This is then modified by adding the non-ideal factors such as limit of op-amp output swing, the finit DC gain of op-amp slew rate, the integrator gian error by the capacitor mismatch, the ADC error by the cmparator offset and the mismatch of resistor string, and the non-linear of DAC. From this modeling, as it is determined the specification of each devices requeired in design and the fabrication error limits, we can see the final performance of modulator.
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14 비트 분해능을 갖는 2차 Sigma-Delta 변조기 설계 및 검증
조병욱,최평,손병기,Cho, Byung-Woog,Choi, Pyung,Sohn, Byung-Ki 대한전자공학회 1999 전자공학회논문지SC (System and control) Vol.s36 No.5
저주파의 아날로그 신호를 디지털 신호로 변환하기 위해 sigma-delta 아날로그-디지털 변환기의 이용이 용이하다. 이 변환기는 변조기와 디지털 필터로 구성되는데 본 논문에서는 변조기에 대해서만 언급한다. 모델링을 통해 14비트 분해능을 갖는 2차 sigma-delta 변조기를 설계하기 위한 변조기의 구성요소 즉 연산 증폭기, 적분기, 내부 ADC 및 DAC의 최대 허용 에러 범위를 규정하였으며, 이를 토대로 연산증폭기, 2비트 ADC 및 DAC 등을 설계·검증하고, 이들을 서로 연결하여 2차 sigma-delta 변조기를 구성하였다. 3비트 ADC의 기준전압을 조절하여 변조기 성능 향상을 도모하였으며, 내부 DAC를 축전기 및 간단한 제어회로로 구성하여 비선형성 에러를 최소화하였다. 설계된 각각의 구성요소들은 모델링에서 정의된 에러 범위를 모두 만족하였으며, 전체 변조기는87㏈의 입력범위와 87㏈의 최대 신호 대 잡음 비를 가졌다.
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조병욱,김영진,김창수,최평,손병기 ( Byung Woog Cho,Young Jin Kim,Chang Soo Kim,Pyung Choi,Byung Ki Sohn ) 한국센서학회 1998 센서학회지 Vol.7 No.1
Multi-channel sensors can be used to increase the reliability and remove the random noise in ion-sensitive field effect transistors(ISFETs). Multi-channel sensors is also an essential step toward potential fabrication of sensors for several ionic species in one device. However, when the multi-channel sensors are separately biased, the biasing problems become difficult, that is to say, the bias circuit is needed as many sensors. In this work, a circuit for biasing the four pH-ISFETs in null-balance method, where bias voltages are switched, was proposed. The proposed concept is need only one bias circuit for the four sensors. Therefore it has advantages of smaller size and lower power consumption than the case that all sensors are separately biased at a time. The proposed circuit was tested with discrete devices and its performance was investigated. In the recent trend, sensor systems are implemented as portable systems. So the verified measurement circuit was integrated by using the CMOS circuit. Fortunately, ISFET fabrication process can be compatible with CMOS process. Full circuit has a mask area of 660㎛ x 500㎛. In the future, this step will be used for developing the smart sensor system with ISFET.
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백금전극과 감광성 고분자를 이용한 ISFET 포도당 및 자당센서의 감지성능 개선
조병욱,장원덕,김창수,박이순,손병기 ( Byuhng Woog Cho,Won Duk Jang,Chang Soo Kom,Lee Soon Park,byung Ki Sohn ) 한국센서학회 1995 센서학회지 Vol.4 No.4
The ISFET glucose and sucrose sensors containing platinum electrode and photopolymeric enzyme membrane were fabricated. The platinum working electrode was used for the electrolysis of hydrogen peroxide, which was the other product of the enzyme reaction, to improve sensing characteristics of the sensors. In order to improve response time, photo-crosslinkable polymer(PVA-SbQ) was used to the matrix for the enzyme immobilized membrane. The characteristics of glucose and sucrose sensors were investigated according to the variation of platinum electrode area. The response time was about 3∼5 minutes and determinations of glucose and sucrose in the range of about 30∼300mg/dl could be possible.
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사진식각기술을 이용한 FET 형 반도체 요소 및 포도당센서의 제조와 그 특성
조병욱,김창수,서화일,손병기 ( Byung Woog Cho,Chang Soo Kim,Hwa Il Seo,Byung Ki Sohn ) 한국센서학회 1992 센서학회지 Vol.1 No.1
pH-ISFETs, the semiconductor pH sensors, were combined with immobilized enzyme membranes to prepare FET type urea and glucose sensors and its operational characteristics were investigated. Photolithography techniques wore applied to immobilize enzymes on the H^+ sensing membrane of the pH-ISFET with photo-sensitive polymers, PVA-SbQ. Fabricated urea and glucose sensors could determine 0.5∼50 mg/dl urea concentrations and 10∼1000 mg/dl glitdbse concentrations, respectively.
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