An extended fukui‐like formula for the minimum‐noise figure of microwave fets

摘要

AbstractThe article presents an extension of the well‐known Fukui formula for the minimum noise figure of microwave FETs, based on a complete small‐signal equivalent circuit including parasitic elements, the feedback capacitance Cgd, and the output admittance (Gdsand Cds). We show that the simplified circuit neglecting all of the above elements, on which most Fukui‐like expressions are based, overestimates NFmin, mainly because Cgdis discarded; moreover, the linear approximation of NFmin(f) from the complete circuit is more accurate than the quadratic one, while parasitic inductances affect the terms of the series expansion of NFminin powers of f from the third order only. © 1994 John WileySon