Hello Uwe,
power-FETs do have rather large gate-source capacitances that can differ
from FET to FET. For the popular IRF450 Cgs is about 2nF, variations
between FET's can easily be a few 100pF. If the FETs are driven from a
rather high-Z source the variations in Cgs might cause a phase shift,
although 10 degrees look very much to me.
How did you measure this phase shift ? In the past I have noticed that
measuring waveforms at the gate of a FET with the drain open can give very
strange results ...
73, Rik ON7YD
Hi all,
guess many of you built the G0MRF-Quarter-Kilowatt-Amplifier.
I did. the PSU is not finished yet.
got some trouble with the phase of the 137kHz sines
(es triangular and rectangular) measured at the gates of the MOSFETs.
there is a diff btwn the two channels of estimated 10degr.
that means parasitic oscillation if operating the PA, doesn`t it.
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