• KSBB Journal
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• v.13 no.5
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• pp.477-482
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• 1998

A biosensor with PZT piezoelectric ceramic crystal was developed for the detection of formaldehyde gas. Poled PZT piezoelectric ceramic disk was made from ZrO2, TiO2 and Nb2O5, together with the addition of PbO and polyvinyl alcohol, through various processes of mixing, calcination drying, crushing, forming, sintering, polishing, ion coating and poling. Oscillator circuit of sensor was made of operational amplifier(AD811AN). Formaldehyde dehydrogenase was immobilized onto a piezoelectic ceramic crystal, together with the cofactors, reduced glutathione and nicotinamide adenine dinucleotide. The effect of flow rate on the sensitivity was determined by varing the flow rate of carrier gas from 24.7mL/min to 111.7mL/min through detector cell. The results indicated that as the flow rate was increased, the recovery rate was increased. And a significant increase in the sensitivity was observed in enhanced flow rate of carrier gas. Frequency difference(ΔF) of immobilized PZT piezoelectic disk increased proportionally to the concentration gas and reproduced to repeated exposures of formaldehyde gas(28ppm, Δ68Hz).

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.2 s.173
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• pp.355-361
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• 2000

In this study, active control magnetic actuator for reducing vibration of rotor system is performed. Identification, modeling, simulation, control system design, and evaluation of active magnetic damper system have been researched. Power amplifier modeling, connected magnetic actuator and augmented by system identification, is included to establish a magnetic damper simulation which provides close performance correspondence to the physical plant. A magnetic actuator, digital controller using DSP(Digital Signal Processor), and bipolar operational power supply/amplifiers are developed to show the effectiveness of reducing rotor vibration. Also the curve fitting procedure to obtain the transfer function of frequency dependent components is developed. Two kinds of test are executed as sliding and oil bearing. Results presented in this paper will provide a well-defined technical parameters in designing magnetic damper system for the proposed rotor.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.10
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• pp.1448-1453
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• 2012

In this study, we carried out transient radiation test for identify failure situation by a transient radiation effect on operational amplifier devices. This experiments were carried out using a 60 MeV electron beam pulse of the LINAC(Linear Accelerator) facility in the Pohang Accelerator Laboratory. In this test, we has found that a serious failure as a burn-out effect due to overcurrent on the partial electronic devices.

• Journal of information and communication convergence engineering
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• v.6 no.3
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• pp.275-278
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• 2008

In this paper, I propose the full CMOS FLL(frequency locked loop) circuit. The proposed FLL circuit has a simple structure which contains a FVC(frequency-to-voltage converter), an operational amplifier and a VCO(voltage controlled oscillator). The operation of FLL circuit is based on frequency comparison by the two FVC circuit blocks. The locking time of FLL is short compared to PLL(phase locked loop) circuit because the output signal of FLL is synchronized only in frequency. The circuit is designed by 0.35${\mu}m$ process and simulation carried out with HSPICE. Simulation results are shown to illustrate the performance of the proposed FLL circuit.

• Proceedings of the KIEE Conference
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• 1999.11c
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• pp.693-696
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• 1999

This paper describes a new voltage recorder for the voltage management of a power distribution line by using a new voltage measurement technique. The RMS(Root Mean Square) voltage measurement for the power line under the assumption of a sinusoidal input voltage is taken by the full-wave rectifier, half-adder utilizing operational amplifier(OP) circuit. A/D converter utilizing a dual slope converter converts an analog voltage signal into a serial pulse. The pulse is counted with a single chip micro-controller, converted with the RMS voltage, and saved into a flash memory. In the last, a new voltage recorder with compact size and multifunction is developed. Also, Voltage Management System that can analyze the stored data via RS-232C cable is developed based on Windows 95 and Visual C++.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.8
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• pp.1260-1264
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• 1990

A voltage controlled CMOS operational transconductance amplifier (OTA), whose transconductance is directly proportional to the DC bias voltage, has been designed for many electronic circuit applications. It consists of a differential pair and three ourrent mirrors. The SPICE simulation shows that the conversion sensitivity of the OTA is 41.817 \ulcornerho/V and the linearity error is less than 0.402% over a bias voltage range from -2. OV to 1. OV. Electrically tunalble filters based on voltage controlled impedances, which are realized with OTA's, also have been designed. The SPICE simulation shows that a second-order bandpass filter, whose center frequency is 23KHz at -1. OV, has the conversion sensitivity 6.6KHz/V and the linearity error less than 0.822% over a voltage range from -2.OV tp 1.OV, Tne OTA has been laid out with the 3\ulcorner n-well CMOS design rule adopted in ISRC (inter-university semiconductor research center). The chip size was about $0.756x0.945mm^2$.

• Journal of Industrial Technology
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• v.22 no.B
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• pp.133-139
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• 2002

In precision instrumentation system, an A/D conversion of signal conditioning has been always suffered from some problems ; offset and drift voltage with environmental situation. This paper suggests a method of reducing the offset voltage and the drift error from the A/D conversion hardware using analog signal switching technique with specific operational amplifier circuits. Also, we have designed a hardware active filter and a software digital filter with Auto Zero Tracking algorithm for better dignal process of the our proposed weighing system. Software technique was performed to obtain the stable data from A/D converter. As a result of our experimental works, the proposed system is expected to be used in the industrial field where a high precision measurement is required.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.72-75
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• 2003

For the analog output buffer in the data driver for large size and high resolution TFT-LCDs, we proposed operational amplifier (op-amp) which contains newly developed transconductance-boosted input stage which enables the low-power consumption and the high slew-rate. The slew-rate and the quiescent current of the proposed op-amp are $6.1V/{\mu}sec$ and $8{\mu}A$, respectively.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.686-689
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• 2003

This paper describes two kind of new concept for low power consumption for small area TFT-LCDs. First, the proposed analog buffer could reduce the static current by adopting new scheme. Second, new data driver structure reduced DC power consumption by reducing the number of operational amplifier (op-amp). As simulation results of Hspice, the quiescent current of proposed analog buffer is less than $0.8{\mu}A$ and the DC power consumption is reduced about $40{\sim}50%$ compared with conventional ones.

• Proceedings of the KIEE Conference
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• 2001.11c
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• pp.38-41
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• 2001

To reduce the wasted power with using an OP-AMP, 3 circuit supplying the same amount of power to load through overall voltage range can able proposed. With this type of design, the power that induced to the devices in the circuit will be reduced, we can also develope a small size power supply with the OP-AMP developed using this design. If we need a OP-AMP needed to handle higher power than usual, another design technique can be proposed. With substituting one device with the devices connected in series, the power loaded to each devices in the series devices can be reduced. This thesis contents the design of an OP-AMP to use in high power fields with small thermal dissipation.