• Progress in Superconductivity
• /
• v.4 no.1
• /
• pp.37-41
• /
• 2002

In this work. we have designed two different kinds of Rapid Single Flux Quantum (RSFQ) OR-gates. One was based on the already developed RSFQ cells and the other was aimed to develop a more compact version. In the first circuit, we used a combination of two D Flip-Flops and a merger and in the other circuit we used a combination of RS Flip-Flops and Confluence Buffer. We tested the circuit performance by using the simulation tools, Xic and Wrspice. We obtained the operation margins of the circuit elements by a margin calculation program, and we obtained the minimum operation margins of $\pm$30%. The circuits were laid out, aimed to fabricate by using the existing KRISS Nb process. KRISS Nb process includes the $Nb／Al_2$$O_3$／Nb trilayer fabricated by DC magnetron sputtering and the reactive ion etching technique for the definition of the features. The major tools used in the layouts were Xic and L-meter.

• Journal of the Optical Society of Korea
• /
• v.13 no.3
• /
• pp.386-391
• /
• 2009

PSPICE circuit parameters of the blue laser diodes grown on wurtzite AlGaInN multiple quantum well structures were extracted directly from the three level rate equations. The relevant optical gain parameters were separately calculated from the self-consistent multiband Hamiltonian. The resulting equivalent circuit model for a blue laser diode was schematically presented, and its modulation characteristics, including the pulse response and the frequency response, have been demonstrated by using a conventional PSPICE.

• ETRI Journal
• /
• v.36 no.1
• /
• pp.89-98
• /
• 2014

The integration of digital circuits has a tight relation with the scaling down of silicon technology. The continuous scaling down of the feature size of CMOS devices enters the nanoscale, which results in such destructive effects as short channel effects. Consequently, efforts to replace silicon technology with efficient substitutes have been made. The carbon nanotube field-effect transistor (CNTFET) is one of the most promising replacements for this purpose because of its essential characteristics. Various digital CNTFET-based circuits, such as standard logic cells, have been designed and the results demonstrate improvements in the delay and energy consumption of these circuits. In this paper, a new CNTFET-based 5-input XOR gate based on a novel design method is proposed and simulated using the HSPICE tool based on the compact SPICE model for the CNTFET at the 32-nm technology node. The proposed method leads to improvements in performance and device count compared to the conventional CMOS-style design.

• Progress in Superconductivity and Cryogenics
• /
• v.20 no.4
• /
• pp.6-10
• /
• 2018

Low-noise amplifiers in the radio-frequency (RF) band based on the direct current (DC) superconducting quantum interference device (SQUID) can be used for quantum-limited measurements in precision physics experiments. For the prediction of peak-gain frequency of these amplifiers, we need a reliable design formula for the resonance frequency of the microstrip circuit. We improved the formula for the resonance frequency, determined by parameters of the DC SQUID and the input coil, and compared the design values with experimental values. The proposed formula showed much accurate results than the conventional formula. Minor deviation of the experimental results from the theory can be corrected by using the measured geometrical parameters of the input coil line.

• Applied Chemistry for Engineering
• /
• v.30 no.4
• /
• pp.499-503
• /
• 2019

Characteristics of solar cells employing a lattice matched GaInP/GaAs quantum well (QW) structure in a single N-AlGaInP/p-InGaP heterojunction (HJ) were investigated and compared to those of solar cells without QW structure. The epitaxial layers were grown on a p-GaAs substrate with $6^{\circ}$ off the (100) plane toward the <111>A. The heterojunction of solar cell consisted of a 400 nm N-AlGaInP, a 590 nm p-GaInP and 14 periods of a 10 nm GaInP/5 nm GaAs for QW structure and a 800 nm p-GaInP for the HJ structure (control cell). The solar cells were characterized after the anti-reflection coating. The short-circuit current density for $1{\times}1mm^2$ area was $9.61mA/cm^2$ for the solar cell with QW structure while $7.06mA/cm^2$ for HJ control cells. Secondary ion mass spectrometry and external quantum efficiency results suggested that the significant enhancement of $J_{sc}$ and EQE was caused by the suppression of recombination by QW structure.

• Progress in Superconductivity
• /
• v.7 no.1
• /
• pp.36-40
• /
• 2005

The problem of fluctuation-induced digital errors in a rapid single flux quantum (RSFQ) circuit has been a very important issue. In this work, we calculated the bit error rate of an RSFQ switch used in superconductive arithmetic logic unit (ALU). RSFQ switch should have a very low error rate in the optimal bias. Theoretical estimates of the RSFQ error rate are on the order of $10^{-50}$ per bit operation. In this experiment, we prepared two identical circuits placed in parallel. Each circuit was composed of 10 Josephson transmission lines (JTLs) connected in series with an RSFQ switch placed in the middle of the 10 JTLs. We used a splitter to feed the same input signal to both circuits. The outputs of the two circuits were compared with an RSFQ exclusive OR (XOR) to measure the bit error rate of the RSFQ switch. By using a computerized bit-error-rate test setup, we measured the bit error rate of $2.18{\times}10^{-12}$ when the bias to the RSFQ switch was 0.398 mA that was quite off from the optimum bias of 0.6 mA.

• Journal of international Conference on Electrical Machines and Systems
• /
• v.3 no.3
• /
• pp.317-324
• /
• 2014

The forces involved in the firing of the electromagnetic rail gun may be analyzed from Amperian, Maxwellian and Einsteinian approaches. This paper discusses these different paradigms with regard to rail gun performance modeling relating to the generation and balance of the forces caused by the currents and their induced magnetic fields. Recent experimental work on model rail guns, where the armature is held static, shows very little recoil upon the rails, thereby indicating a possible violation of Newton's Third Law of Motion. Dynamic testing to show this violation, as suggested by the authors in an earlier paper, has inherent technical difficulties. A purpose-built finite element C/C++ simulator that models that suspended rail gun firing action shows a net force acting upon the entire rail gun system. A new effect in physics, universal in scope, is thus indicated: a current circulating in an asymmetric and rigid circuit causes a net force to act upon the circuit for the duration of the current. This conclusion following from computer simulation based upon Maxwellian electrodynamics as opposed to the more modern relativistic quantum electrodynamics needs to be supported by unambiguous experimental validation.

• Journal of Radiation Industry
• /
• v.6 no.1
• /
• pp.31-40
• /
• 2012

There are two methods to fabricate the readout electronic to a large-area CMOS image sensor (LACIS). One is to design and manufacture the sensor part and signal processing electronics in a single chip and the other is to integrate both parts with bump bonding or wire bonding after manufacturing both parts separately. The latter method has an advantage of the high yield because the optimized and specialized fabrication process can be chosen in designing and manufacturing each part. In this paper, LACIS chip, that is optimized design for the latter method of fabrication, is presented. The LACIS chip consists of a 3-TR pixel photodiode array, row driver (or called as a gate driver) circuit, and bonding pads to the external readout ICs. Among 4 types of the photodiode structure available in a standard CMOS process, $N_{photo}/P_{epi}$ type photodiode showed the highest quantum efficiency in the simulation study, though it requires one additional mask to control the doping concentration of $N_{photo}$ layer. The optimized channel widths and lengths of 3 pixel transistors are also determined by simulation. The select transistor is not significantly affected by channel length and width. But source follower transistor is strongly influenced by length and width. In row driver, to reduce signal time delay by high capacitance at output node, three stage inverter drivers are used. And channel width of the inverter driver increases gradually in each step. The sensor has very long metal wire that is about 170 mm. The repeater consisted of inverters is applied proper amount of pixel rows. It can help to reduce the long metal-line delay.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
• /
• 2003.10a
• /
• pp.127-130
• /
• 2003

An RSFQ (Rapid Single Flux Quantum) counter can be used as a frequency divider that was an essential part of a programmable voltage standard chip. The voltage standard chip is composed of two circuit parts, a counter and an antenna Analog signal of tens to hundreds ㎓ may be applied to a finline antenna part. This analog signal can be converted to the stream of SFQ voltage pulses by a DC/SFQ circuit. The number of voltage pulses can be reduced by 2n times when they pass through a counter that is composed of n T Flip-Flops (Toggle Flip-Flop). Such a counter can be used not only as a frequency divider, but also to build a programmable voltage standard chip. So, its application range can be telecommunication, high speed RAM, microprocessor, etc. In this work, we have used Xic, WRspice, and L-meter to design an RSFQ counter. After circuit optimization, we could obtain the bias current margins of the T Flip-Flop circuit to be above 31％ Our RSFQ counter circuit designs were based on the 1 ㎄/$\textrm{cm}^2$ niobium trilayer technology.

• Journal of Sensor Science and Technology
• /
• v.31 no.2
• /
• pp.115-119
• /
• 2022

A readout circuit for a mercury-cadmium-telluride (MCT)-amplified mid-wave infrared (IR) photodetector was realized and applied to noncontact chemical agent detectors based on a quantum cascade laser (QCL). The QCL emitted 250 times for each wavelength in 0.2-㎛ steps from 8 to 12 ㎛ with a frequency of 100 kHz and duty ratio of 10%. Because of the nonconstant QCL emission power during on-duty, averaging the photodetector signals is essential. Averaging can be performed in digital back-end processing through a high-speed analog-to-digital converter (ADC) or in analog front-end processing through an integrator circuit. In addition, it should be considered that the 250 IR data points should be completely transferred to a PC during each wavelength tuning period of the QCL. To average and minimize the IR data, we designed a readout circuit using the analog front-end processing method. The proposed readout circuit consisted of a switched-capacitor integrator, voltage level shifter, relatively low-speed analog-to-digital converter, and micro-control unit. We confirmed that the MCT photodetector signal according to the QCL source can be accurately read and transferred to the PC without omissions.