• 대한전자공학회논문지
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• 제26권9호
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• pp.1308-1316
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• 1989

A simplified 10-element GaAs MESFET equivalent circuit model has been presented which is suitable for the design of ultrabroad-band microwave small-signal amplification, the these circuit element values are extracted from measured S-parameters using complex-curve fitting algorithm. Packaged GaAs MESFET equivalent circuits are composed of intrinsic \ulcornermodel and several extrinsic elements at microwave frequencies, of which the largest effects are caused by package lead inductances. If these are eliminated from measured S-parameters, newly obtained S-parameters are closed to intrinsic \ulcornermodel, and the rest element values can be easily extracted. The modeling results applied to the packaged GaAs MESFET NE71083 are almost equal between the measure S-parameters and the mideled S-parameters within b 2% errors from DC to 8GHz, and errors are increased to \ulcorner% upto 12GHz wide bandwidth.

• 대한전자공학회논문지
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• 제26권9호
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• pp.1359-1368
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• 1989

In this paper, the composite BiCMOS transistor which combines a bipolar transistor and a MOS transistor in a cascade type, is analyzed in terms of I-V characteristics and small signal equivalent circuit. As a result, it has a larger driving capability than MOS transistor and a more extended rante of input voltage than bipolar transistor. Next, a BiCMOS differential amplifier as its application example is designed and compared with the CMOS one and the bipolar one. It increases the driving capability of the CMOS differential amp and improves the linear operation region of the bipolar differential amp.

• Journal of Power Electronics
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• 제19권5호
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• pp.1326-1335
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• 2019

Common mode (CM) chokes are a crucial part in EMI filters for mitigating the electromagnetic interference (EMI) of switched-mode power supplies (SMPS) and for meeting electromagnetic compatibility standards. However, the parasitic capacitances of a CM choke deteriorate its high frequency filtering performance, which results in increases in the design cycle and cost of EMI filters. Therefore, this paper introduces a negative capacitance generated by a negative impedance converter (NIC) to cancel the influence of equivalent parallel capacitance (EPC). In this paper, based on a CM choke equivalent circuit, the EPCs of CM choke windings are accurately calculated by measuring their impedance. The negative capacitance is designed quantitatively and the EPC cancellation mechanisms are analyzed. The impedance of the CM choke in parallel with negative capacitances is tested and compared with the original CM choke using an impedance analyzer. Moreover, a CL type CM filter is added to a fabricated NIC prototype, and the insertion loss of the prototype is measured to verify the cancellation effect. The prototype is applied to a power converter to test the CM conducted noise. Both small signal and EMI measurement results show that the proposed technique can effectively cancel the EPCs and improve the CM filter's high frequency filtering performance.

• 대한전자공학회논문지SD
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• 제43권10호
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• pp.10-21
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• 2006

850nm oxide VCSEL의 저전류 동작 가능성을 확인하기 위하여 off 전류와 on 전류를 최대한 낮춘 상태에서 VCSEL의 특성을 살펴보았다. Oxide VCSEL의 모델링을 위해 비율 방정식을 이용하여 대신호 등가회로를 만들었고, 실험 결과와 시뮬레이션 결과의 비교를 통해 각각의 계수와 특성변수를 추출하였다. 동특성에 큰 영향을 주는 커패시턴스 성분은 C-V 미터로 측정, 분석하였다. 완성된 대신호 등가회로 모델을 이용하여 커패시턴스 성분, 그리고 on 전류와 off 전류가 turn-on 특성과 turn-off 특성, eye-diagram에 미치는 영향을 분석하였다. 그 결과 지금까지는 무시해왔던 요소인 depletion 커패시턴스가 turn-on 특성에 큰 영향을 미치고, eye-diagram에도 큰 영향을 준다는 사실을 확인하였다. 그러므로 VCSEL의 고속 동작과 저전류 동작을 동시에 구현하기 위해서는 depletion 커패시턴스를 감소시키는 공정이 필요하다.

• 한국정보통신학회논문지
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• 제11권2호
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• pp.330-336
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• 2007

본 논문에서는 디지털 의료 영상 및 진단 분야 그리고 산업용으로도 활용 가능한 싱글 포톤 계수형 영상센서를 $0.18{\mu}m$ triple-well CMOS(Complementary Metal Oxide Semiconductor) 공정을 사용하여 설계하였다. 설계된 Readout 칩용 싱글 픽셀은 디지털 X-ray 이미지 센서모듈을 간단화 하기 위해 단일 전원전압을 사용하였으며, Preamplifier의 출력 전압인 signal voltage(${\Delta}Vs$)를 크게 하기 위해 Folded Cascode CMOS OP amp를 이용한 Preamplifier를 설계하였으며, 기존의 Readout 칩 외부에서 인가하던 threshold voltage를 Readout 칩 내부에서 생성해 줄 수 있도록 Externally Tunable Threshold Voltage Generator 회로를 새롭게 제안하였다. 그리고, Photo Diode에서 발생하는 Dark Current Noise를 제거하기 위한 Dark Current Compensation 회로를 제안하였으며, 고속 counting이 가능하고, layout 면적이 작은 15bit LFSR(Linear Feedback Shift Resister) Counter를 설계하였다.

• Journal of Power Electronics
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• 제18권3호
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• pp.853-862
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• 2018

Frequency coupling in the phase domain is a recently reported phenomenon for phase locked loop (PLL) based three-phase grid-inverter systems. This paper investigates the mechanism and stabilization method for the frequency coupling to the stability of grid-inverter systems. Self and accompanying admittance models are employed to represent the frequency coupling characteristics of the inverter, and a small signal equivalent circuit of a grid-inverter system is set up to reveal the mechanism of the frequency coupling to the system stability. The analysis reveals that the equivalent inverter admittance is changed due to the frequency coupling of the inverter, and the system stability is affected. In the end, retuning the bandwidth of the phase locked loop is presented to stabilize the three-phase grid-inverter system. Experimental results are given to verify the analysis and the stabilization scheme.

• 한국전자파학회지:전자파기술
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• 제2권2호
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• pp.30-37
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• 1991

GaAs MESFET의 소신호 등가 모델에서 외부 푀로 성분들을 결정하는 개선된 방법을 제시하였다. 정화간 내부 회로 성분값들을 구하기 위하여 외부 회로 성분들을 제거하는 것이 중요하다. 전송선로를 포함한 기생 인덕터와 커패시터로 이루어지 ㄴ외부 회로를 정립하고, 산란 행렬로부터 이들의 값을 구한 후에 내부 회로 성분을 구하였다. 특히 기생 인덕턴스와 커패시턴스값들은 주파수에 따라 거의 일정한 변화를 보였다.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2005년도 춘계학술대회논문집
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• pp.467-472
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• 2005

In this paper, design and control of the novel SEPIC-Flyback converter(SF converter) is developed as a possible converter for fuel cell system. This output characteristic of SF converter is similar to Buck-Boost converter in that it can step-up or step-down the voltage. With the small signal equivalent circuit modeling of SF converter, control-to-output transfer function is obtained. SF converter couples up the inductive type converter to capacitive type converter with one transformer, which has less ripple current than its respective one does. To verify the validity of the proposed converter, 500W, 100kHz converter is designed and tested. ZVS switching and active clamping are also tested in practice.

• 전자공학회논문지A
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• 제32A권1호
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• pp.129-137
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• 1995

AlGaAs/GaAs HBTs have been fabricated using SABM (Self-Aligned Base Metal) process technique. The mesa type HBTs were fabricated through following steps: isolation implant, wet etching, metal lift-off, and airbridge interconnection process. The fabricated HBTs with 2umx10um size emitter showed a common emitter current gain of 10 at a collector current density of Jk=100kA/cm$^{2}$, a breakdown volgate BVCEO of 8V, and the ideality factors of base and collector junctions of 1.6 and 1.1, respectively. On-wafer S-Parameter measurement at 0.5~18GHz has been made for the characterization of the common emitter HBTx with a 2umx10um size emitter. The extrapolated current gain cut-off frequency of ft=30GHz and maximum oscillation frequency of fmax=23 GHz were obtained at a collector current density of Jc=70kA/cm$^{2}$. Small signal HBT equivalent circuit was extracted from the S-Parameter data.

• Transactions on Electrical and Electronic Materials
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• 제7권3호
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• pp.103-107
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• 2006

In this paper, a CMOS complementary bridge rectifier for driving RFID transponder chips is presented. The proposed RFID CMOS complementary bridge rectifier is designed with two NMOSs at the input, which are configured by cross-connected gate structures, and two PMOSs and two NMOSs at the output, which are configured by diode-connected MOS structures. Output characteristics of the proposed rectifier are analyzed with the high frequency small-signal equivalent circuit and verified with SPICE for RFID operating frequencies of 13.56 MHz HF for ISO 18000-3, 915MHz UHF for ISO 18000-6, and 2.45 GHz microwave for ISO 18000-4. Simulation results show well-rectified and high enough DC output voltages for driving the low power microchip in the RFID transponder for the frequency range from HF to microwave. DC output voltages are dropped by only around 0.7 V from the input peak-to-peak voltages.