• Journal of the Institute of Electronics Engineers of Korea SC
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• v.37 no.2
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• pp.29-36
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• 2000

The principle and design of two-stage CMOS operational amplifier with rail-to-rail input and class-AB output stage is presented. The rail-to-rail input stage shows almost constant transconductance independent of the common mode input voltage range in global transistor operation region. This new technique does not make use of accurate current-voltage relationship of MOS transistors. Hence it was achieved by using simple linear relationship of currents. The simulated transconductance variation using SPICE is less the 4.3%. The proposed global two-stage opamp can operate both in strong inversion and in weak inversion. Class AB output stage proposed also has a full output voltage swing and a well-defined quiescent current that does not depend on power supply voltage. Since feedback class- AB control is used, it is expected that this output stage can be operating in extremely low voltage. The variation of DC-gain and unity-gain frequency is each 4.2% and 12%, respectively.

• Journal of electromagnetic engineering and science
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• v.14 no.4
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• pp.393-398
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• 2014

A highly efficient dual-mode linear CMOS stacked-FET power amplifier (PA) is implemented for 3G UMTS and 4G LTE handset applications. High efficiency is achieved at a backed-off output power ($P_{out}$) below 12 dBm by employing an active-bypass amplifier, which consumes very low quiescent current and has high load-impedance. The output paths between high- and low-power modes of the PA are effectively isolated by using a bypass switch, thus no RF performance degradation occurs at high-power mode operation. The fabricated 900 MHz CMOS PA using a silicon-on-insulator (SOI) CMOS process operates with an idle current of 5.5 mA and shows power-added efficiency (PAE) of 20.5%/43.5% at $P_{out}$ = 12.4 / 28.2 dBm while maintaining an adjacent channel leakage ratio (ACLR) better than -39 dBc, using the 3GPP uplink W-CDMA signal. The PA also exhibits PAE of 35.1% and $ACLR_{E-UTRA}$ of -33 dBc at $P_{out}$ = 26.5 dBm, using the 20 MHz bandwidth 16-QAM LTE signal.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.1
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• pp.80.1-80.1
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• 2015

We present a study of outflows on 24 embedded young stellar objects selected from the source list of the Dust, Ice, and Gas in Time (DIGIT) Herschel key program. To study the relation between the CO outflows observed in low-J transitions and the properties of protostars more consistently with a homogeneous data set, we mapped the CO outflows of the selected targets in the J = 1-0 and J = 2-1 lines with two Korean telescopes (SRAO and TRAO). We compare CO outflow force ($F_{CO}$) with the bolometric luminosity, ($L_{bol}$) bolometric temperature, and the FIR molecular line luminosities of CO, $H_2O$, OH, and [O I] detected by the Herschel-PACS observations. We find that $F_{CO}$ of J = 1-0 is greater than that of 2-1 by a factor of ~ 2. The well known correlation between $F_{CO\;2-1}$ and $L_{bol}$ is not very evident in our sample as a whole, but they show a rather strong correlation when IRAM 04191+1522 is excluded. IRAM 04191+1522 has relatively high $F_{CO\;2-1}$ in spite of its low $L_{bol}$. This object is a well-known VeLLO, which is believed in the quiescent phase of the episodic mass accretion in the embedded stage. $L_{bol}$ traces a current accretion, but $F_{CO\;2-1}$ traces accretion happened long ago. Therefore, the low-$L_{bol}$ with the high-$F_{CO\;2-1}$ can be explained by the episodic accretion. $F_{CO\;2-1}$ shows little correlation with individual FIR line luminosities of CO, $H_2O$, OH, while [O I] and total FIR line luminosity seem to have correlations with $F_{CO\;2-1}$. This result is interpreted as the accretion energy deposits on species differently depending on shock properties, but the total FIR line luminosity sums the total accretion energy dispersed to different species.