4 research outputs found

    Synthesis of a Complex Prototype Ladder Filter Excluding Inductors with Finite Transmission Zeros Suitable for Fully Differential Gm-C Realization

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    In this letter, an active complex filter with finite transmission zeros is proposed. In order to obtain a complex prototype ladder filter including no inductors, a new circuit transformation is proposed. This circuit is classified into the RiCR filter. It is shown that it includes no negative capacitors when it is obtained through a frequency transformation. The validity of the proposed method is confirmed through computer simulation

    Evolution of the Fe-3dd impurity band state as the origin of high Curie temperature in p-type ferromagnetic semiconductor (Ga,Fe)Sb

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    (Ga1x_{1-x},Fex_x)Sb is one of the promising ferromagnetic semiconductors for spintronic device applications because its Curie temperature (TCT_{\rm C}) is above 300 K when the Fe concentration xx is equal to or higher than ~0.20. However, the origin of the high TCT_{\rm C} in (Ga,Fe)Sb remains to be elucidated. To address this issue, we use resonant photoemission spectroscopy (RPES) and first-principles calculations to investigate the xx dependence of the Fe 3dd states in (Ga1x_{1-x},Fex_x)Sb (xx = 0.05, 0.15, and 0.25) thin films. The observed Fe 2pp-3dd RPES spectra reveal that the Fe-3dd impurity band (IB) crossing the Fermi level becomes broader with increasing xx, which is qualitatively consistent with the picture of double-exchange interaction. Comparison between the obtained Fe-3dd partial density of states and the first-principles calculations suggests that the Fe-3dd IB originates from the minority-spin (\downarrow) ee states. The results indicate that enhancement of the interaction between ee_\downarrow electrons with increasing xx is the origin of the high TCT_{\rm C} in (Ga,Fe)Sb
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