• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.7
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• pp.44-51
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• 2008

A stereo audio digital-to-analog converter (DAC) with a power amplifier using asymmetric pulse-width modulation (PWM) is presented. To adopt class-D amplifier mainly used in high-power audio appliances for head-phones application, this work analyzes the noise caused by the inter-channel interference during the integration and optimizes the design of the sigma-delta modulator to decrease the performance degradation caused by the noise. The asymmetric PWM is implemented to reduce switching noise and power loss generated from the power amplifier. This proposed architecture is fabricated in 0.13-mm CMOS technology. The proposed audio DAC including the power amplifier with single-ended output achieves a dynamic range (DR) of 95-dB dissipating 4.4-mW.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.3
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• pp.1700-1706
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• 2014

In this paper, a step down converter for LED backlight of mobile application has been proposed. The converter which is operated with 4 MHz high switching frequency is capable of reducing mounting area of passive devices consists of a power stage and a control block. Circuit elements of the power stage are inductor, output capacitor, MOS transistors and feedback resistors. The control block consists of pulse width modulator, error amplifier and oscillator etc. Proposed step down converter has been designed and verified using a $0.35{\mu}m$ 1-poly 4-metal BCD process technology. Simulation results show that the output voltage is 1.8 V in 3.7 V input voltage, output current 100 mA which is larger than 25 ~ 50 mA in conventional 500 KHz driven converter when the duty ratio is 0.4.

• Korean Journal of Optics and Photonics
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• v.10 no.2
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• pp.146-151
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• 1999

We demonstrated a harmonic mode locking scheme that used regeneratie phase modulation to get a high and stable repetition rate in a figure-of-eight fiber soliton laser. From the detected beat spectra of the laser output, a sinusoidal clock freguency tone of 400 MHz, the 96th harmonics of the fundamental mode locking frequency, was extracted with a high Q filter and was used to drive the phase modulator, resulting in stable output of soliton pulse train synchronized with the modulation signal. Generated soliton pulses had FWHM pulsewidth of 930 fs and 3.1 nm linewidth, yielding pulsewidth-bandwidth product of 0.359 that was close to the transform limit. As the modulation frequency always followed the beat frequency of laser modes, stable harmonic mode locking was achieved without the adjustment of the cavity length, which has been commonly required in actively mode-locked lasers.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.3
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• pp.517-526
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• 2008

A one-chip DC-DC converter circuit for OLED(Organic Light-Emitting Diode) display module of automotive clusters is newly proposed. OLED panel driving voltage circuit, which is a charge-pump type, has improved characteristics in miniaturization, low cost and EMI(Electro-Magnetic Interference) compared with DC-DC converter of PWM(Pulse Width Modulator) type. By using bulk-potential biasing circuit, charge loss due to parasitic PNP BJT formed in charge pumping, is prevented. In addition, the current dissipation in start-up circuit of band-gap reference voltage generator is reduced by 42% and the layout area of ring oscillator is reduced by using a logic voltage VLP in ring oscillator circuit using VDD supply voltage. The driving current of VDD, OLED driving voltage, is over 40mA, which is required in OLED panels. The test chip is being manufactured using $0.25{\mu}m$ high-voltage process and the layout area is $477{\mu}m{\times}653{\mu}m$.

• Development and Reproduction
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• v.12 no.3
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• pp.267-274
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• 2008

Differentiation of blastocyst is critical step for implantation and is under the control of regulation factors originated from embryo or reproductive tracts. The sequential communication with those factors is suspected as critical events for differentiation. It has been suggested that intracellular signaling pathways activated by calcium is essential in differentiation of blastocyst. Previously, it was known that concanavalin A (Con A) increase the levels of free calcium in blastocyst stage. However, Con A can not accelerate the hatching, although heparin-binding epidermal growth factor-like growth factor (HB-EGF), a modulator of calcium level, accelerate the hatching of blastocyst. In this study, it was investigated whether Con A or prostaglandin $E_2$ ($PGE_2$) can modulate the differentiation of blastocyst. Con A accelerated the expansion of blastocyst in both 1 hr pulse treatment group and continuous treatment group. However, Con A significantly suppressed the hatching in both groups. The inhibition was significantly strong in continuous treatment group compared with 1 hr pulse treatment group. On the other hand, $PGE_2$ induced the increase the free calcium level, but did not accelerate the expansion. In addition $10{\mu}m\;PGE_2$ inhibited hatching. However, $PGE_2$ could accelerate hatching in Con A pretreated blastocyst. $PGE_2$ also caused the increase of free calcium level in Con A pretreated blastocyst. From these results, it is suggested that changes of the free calcium level induce a different calcium-mediated signaling pathways. In addition, sequential stimulation by signal molecules may triggers the cellular mechanisms for the differentiation of blastocyst.

• Journal of the Korean Society for Nondestructive Testing
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• v.24 no.5
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• pp.499-507
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• 2004

We have studied tile detection techniques, which can determine the location and the weight of an intruder into infrastructure, by using fiber-optic ROTDR (Rayleigh optical time domain reflectometry) sensor and fiber-optic BOTDA (Brillouin Optical time domain analysis) sensor, which can use an optical fiber longer than that of ROTDR sensor Fiber-optic sensing plates of ROTDR sensor, which arc buried in sand, were prepared to respond the intruder effects. The signal of ROTDR was analyzed to confirm the detection performance. The constructed ROTDR could be used up to 10km at the pulse width of 30ns. The location error was less than 2 m and the weight could be detected as 4 grades, such as 20kgf, 40kgf, 60kgf and 80kgf. Also, fiber optic BOTDA sensor was developed to be able to detect intrusion effect through an optical fiber of tells of kilometers longer than ROTDR sensor. fiber-optic BOTDA sensor was constructed with 1 laser diode and 2 electro-optic modulators. The intrusion detection experiment was peformed by the strain inducing set-up installed on an optical table to simulate all intrusion effect. In the result of this experiment, the intrusion effort was well detected as the distance resolution of 3m through the fiber length of about 4.81km during 1.5 seconds.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.6
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• pp.2747-2753
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• 2011

In this paper, a PWM current-mode DC-DC boost converter for mobile phone flash application has been proposed. The converter which is operated with 5 Mhz high switching frequency is capable of reducing mounting area of passive devices such as inductor and capacitor, consequently is suitable for compact mobile phones. This boost converter consists of a power stage and a control block. Circuit elements of the power stage are inductor, output capacitor, MOS transistors and feedback resistors. Meanwhile, the control block consists of pulse width modulator, error amplifier, oscillator etc. Proposed boost converter has been designed and verified in a $0.5\;{\mu}m$ 1-poly 2-metal CMOS process technology. Simulation results show that the output voltage is 4.26 V in 3.7 V input voltage, output current 100 mA which is larger than 25 ~ 50 mA in conventional 500 Khz driven converter when the duty ratio is 0.15.