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Re: LF: push/pull

To: [email protected]
Subject: Re: LF: push/pull
From: "jannsen" <[email protected]>
Date: Tue, 14 Jan 2003 18:17:28 +0100
References: <[email protected]> <[email protected]> <[email protected]> <[email protected]>
Reply-to: [email protected]
Sender: <[email protected]>
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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