Rik Strobbe schrieb:
Hello Uwe,
.........
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
Dear Rik, Alberto, Jim es all,
tks for the responses.
yes Rik, the drains were open. the PSU was not finished.
but today I connected in a first step 50V operating voltage to the PA.
I can`t belief it: the phase shift has diminished to abt 2dgr.
I know from my other PA, a two channel N-/P-MOSFET equipment, that the
scope is ok. but I didn`t measure without the PA operating voltage
connected.
yes, the Cgs of the IRFP450/451 is vy high. that is the reason I use in
the other PA many of the weaker MOSFETs IRF620 for the one channel
and IRF9622 for the other. you don`t need the high input power.
tks Alberto es Jim that you do not blame on me or my (in)ability doing the
things right but suspecting the scope.
regards
Uwe/dj8wx
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