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Date: Fri, 10 Aug 2012 08:21:35 +1000
Message-ID: <CAKvcm2fPh08z2jFiBEvOXzvr1pO8SX=qbxA21SFvSNUqhXc4cw@mail.gmail.com>
From: Dimitrios Tsifakis <dtsifakis@gmail.com>
To: rsgb_lf_group@blacksheep.org
Subject: Re: LF: Caps for Class-E amp
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> Well, that's why I thought the monster IXYS FET I used, which is
> obviously an overkill, will probably be hard to kill. I can't possibly
> exceed the 55 A current limit (it's fused to much less than that)
>
> However the peak current in the class E is much higher than the average DC
> current of the supply/battery. 55A peak current at 12V DC supply voltage and
> 100W RF power is not to unrealistic, if the load impedance is a bit
> sub-optimal ;-)

The simulator tells me that the peak to peak current across the FET
(at 200 W output)  is about 24 A. Long way from 55 A, so we should be
fine.

When /p, I will be probably using a single 12 V battery which will
result in about 50 W output. The FET will be half asleep at that power
level ;-)

> What type of IXYS FET do you use?

IXFN55N50. That's what I was given. By the way, I like the screw
terminal FETs, if I ever blow this up, I can easily replace it
in-situ! ;-)

> For a 24V 200W class E is would use a IRFP260N. Just for fun, that one would
> be nice too: IRFP4568 Check out that data sheet. May be a bit hard to drive
> the gate at 137 kHz, maybe to hard for a ICL7667 but a IXDD614 will have no
> problem at all.
>
> Sorry, i just like the topic. Of course your concept will work too!

The Ciss is quite similar to the one I am using now - ~10 nF, so I am
thinking that the TC4420 will probably be OK to drive the IRFP4568,
but if not, I would use a TC4422. Both these FET drivers are cheap on
eBay.

I like the topic too! It's like being in a candy store, which FET
should you use first! I like them all ;-)

73, Dimitris