A monolithic microwave integrated circuit （MMIC） power amplifier （PA） is proposed. It adopts a new on-chip bias circuit, which not only avoids the instability of the direct current bias caused by the change in the...A monolithic microwave integrated circuit （MMIC） power amplifier （PA） is proposed. It adopts a new on-chip bias circuit, which not only avoids the instability of the direct current bias caused by the change in the power supply and temperature, but also compensates deviations caused by the increase in input power. The bias circuit is a current-mirror configuration, and the feedback circuit helps to maintain bias voltage at a constant level. The gain of the feedback circuit is improved by the addition of a non-inverting amplifier within the feedback circuit. A shunt capacitor at the base node of the active bias transistor enhances the linearity of the PA. The chip is fabricated in an InGaP/GaAs heterojunction bipolar transistor （HBT） process. Measured results exhibit a 26. 6-dBm output compression point, 33.6% power-added efficiency （PAE） and - 40.2 dBc adjacent channel power ratio （ACPR） for wide-band code division multiple access （W-CDMA） applications.展开更多
We theoretically investigate the wave-vector and temperature-dependent electron transport in a magneticnanostructure modulated by an applied bias.The large spin-polarization can be achieved in such a device,and the de...We theoretically investigate the wave-vector and temperature-dependent electron transport in a magneticnanostructure modulated by an applied bias.The large spin-polarization can be achieved in such a device,and the degreeof spin-polarization strongly depends on the transverse wave-vector and the temperature.These interesting propertiesmay be helpful to spin-polarize electrons into semiconductors,and this device may be used as a spin filter.展开更多
The general analysis of the forward AC behavior of a semiconductor diode under series mode is pre- sented for the first time.A new method without any particular assumption to characterize a diode was developed. This m...The general analysis of the forward AC behavior of a semiconductor diode under series mode is pre- sented for the first time.A new method without any particular assumption to characterize a diode was developed. This method can accurately measure the dependence of series resistance, junction capacitance, junction vol- tage, ideality factor, and interfacial layer impedance on forward biases. The measurements confirm that the ne- gative capacitance (NC) of Schottky diode is an effect of the junction, and the interfacial layer can be consi- dered as a layer structure with nonlinear resistance and capacitance.展开更多
We propose a scheme for the effective polarization and manipulation of electron spin by using a quantum dot with both charge and spin bias. Using the equation of motion for Keldysh nonequilibrium Green function, we st...We propose a scheme for the effective polarization and manipulation of electron spin by using a quantum dot with both charge and spin bias. Using the equation of motion for Keldysh nonequilibrium Green function, we study the spin accumulation and polarization for the system. Through analytical analysis and a few numerical examples, it is demonstrated that fairly large spin accumulation and polarization can be produced due to the breaking symmetry of the chemical potential for different electron spin in the leads. Moreover, the direction and the strength of the spin polarization can be conveniently controlled and tuned by varying the charge bias or the gate voltage.展开更多
基金The National High Technology Research and Development Program of China(863 Program)(No.2009AA01Z260)
文摘A monolithic microwave integrated circuit （MMIC） power amplifier （PA） is proposed. It adopts a new on-chip bias circuit, which not only avoids the instability of the direct current bias caused by the change in the power supply and temperature, but also compensates deviations caused by the increase in input power. The bias circuit is a current-mirror configuration, and the feedback circuit helps to maintain bias voltage at a constant level. The gain of the feedback circuit is improved by the addition of a non-inverting amplifier within the feedback circuit. A shunt capacitor at the base node of the active bias transistor enhances the linearity of the PA. The chip is fabricated in an InGaP/GaAs heterojunction bipolar transistor （HBT） process. Measured results exhibit a 26. 6-dBm output compression point, 33.6% power-added efficiency （PAE） and - 40.2 dBc adjacent channel power ratio （ACPR） for wide-band code division multiple access （W-CDMA） applications.
基金the USTC Research Funds of the Double First-Class Initiative(YD3420002002)the Youth Innovation Promotion Association CAS(2020451)Fundamental Research Funds for the Central Universities(WK3420000011).
基金Supported by Hubei Province Key Laboratory of Systems Science in Metallurgical Process (Wuhan University of Science and Technology) under Grant No.C201018 the National Natural Science Foundation of China under Grant No.10805035
文摘We theoretically investigate the wave-vector and temperature-dependent electron transport in a magneticnanostructure modulated by an applied bias.The large spin-polarization can be achieved in such a device,and the degreeof spin-polarization strongly depends on the transverse wave-vector and the temperature.These interesting propertiesmay be helpful to spin-polarize electrons into semiconductors,and this device may be used as a spin filter.
文摘The general analysis of the forward AC behavior of a semiconductor diode under series mode is pre- sented for the first time.A new method without any particular assumption to characterize a diode was developed. This method can accurately measure the dependence of series resistance, junction capacitance, junction vol- tage, ideality factor, and interfacial layer impedance on forward biases. The measurements confirm that the ne- gative capacitance (NC) of Schottky diode is an effect of the junction, and the interfacial layer can be consi- dered as a layer structure with nonlinear resistance and capacitance.
基金Supported by the Guizhou Province Governor Foundation for Excellent Talents in Science and Education under Grant No.200847the Research Found of Qiannan Normal College for Nationalities under Grant No.2008Y19
文摘We propose a scheme for the effective polarization and manipulation of electron spin by using a quantum dot with both charge and spin bias. Using the equation of motion for Keldysh nonequilibrium Green function, we study the spin accumulation and polarization for the system. Through analytical analysis and a few numerical examples, it is demonstrated that fairly large spin accumulation and polarization can be produced due to the breaking symmetry of the chemical potential for different electron spin in the leads. Moreover, the direction and the strength of the spin polarization can be conveniently controlled and tuned by varying the charge bias or the gate voltage.
