With todays knowledge, the usage of a MOSFETs in the front stage of an active e-field impedance converter is not really a good idea. Even if some professional active-monopoles like the Eastern German KAA1000 with its made-in-Russia KP902A Power-MOSFET went this way in the past. The noise of as MOSFET is much higher compared to a JFET.? You should also avoid a series resistors to the gate or keep it as small as possible, its thermal noise voltage adds to the signal and degrades the noise figure. That 's why i would not recommend the fig.2 circuit in this article.
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regards
Fred
