MIME-Version: 1.0
In-Reply-To: <ec69cc87-0d8e-7877-1d31-a4ee25fc06ad@n1bug.com>
References: <ec69cc87-0d8e-7877-1d31-a4ee25fc06ad@n1bug.com>
From: Andy Talbot <andy.g4jnt@gmail.com>
Date: Mon, 23 Apr 2018 08:24:13 +0100
Message-ID: <CAA8k23TqoN7dACbCu9t-X5R6J9dD4Z220yuHEUwuk7dXFXZ69Q@mail.gmail.com>
To: LineOne <rsgb_lf_group@blacksheep.org>
Subject: Re: LF: W1VD amp help - MY FINAL POST
Content-Type: multipart/alternative; boundary="f403043e1920b71843056a7eec53"
Sender: owner-rsgb_lf_group@blacksheep.org
Precedence: bulk
Reply-To: rsgb_lf_group@blacksheep.org

--f403043e1920b71843056a7eec53
Content-Type: text/plain; charset="UTF-8"

The irony here is that class-E does not mandate a short sharp gate drive.
As it is tuned and adjusted for zero Drain volts at the transition, the
shape of the drive is less critical.

So says Fred Raab, the guru of using low cost mosfets at HF.   It may not
be quite so true for LF, but I went to a talk given by Fred many years ago
on this subject, and have seen several papers by him.

However, my 400 Watt 475kHz amp does have a nice meaty driver chip.
http://www.g4jnt.com/QRO_500kHz_PA_Breadboard.pdf

(Yes I know it's the 500kHz version - somehow never got round to updating
the write up after retuning for 475kHz)

Andy  G4JNT

On 22 April 2018 at 18:23, N1BUG <paul@n1bug.com> wrote:

> Since I am considering an upscaled version of my current class E
> amplifier, I put that back on the bench and was taking some
> measurements. It uses a single 34N20 FET. In particular I looked at
> the gate waveform with the same scope, probes, and settings I've
> been using with the W1VD deck. I was shocked at how steep the rise
> and fall times are and how it seems to 'power through' the FET
> turn-on anomaly. This stands in stark contrast to the W1VD deck with
> its slow gate rise/fall and long hiccup at FET turn on. At least I
> know the scope is capable of displaying a 'crisp' gate waveform. ;-)
>
> Paul N1BUG
>
>
>
>
>

--f403043e1920b71843056a7eec53
Content-Type: text/html; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

<div dir=3D"ltr">The irony here is that class-E does not mandate a short sh=
arp gate drive.=C2=A0 As it is tuned and adjusted for zero Drain volts at t=
he transition, the shape of the drive is less critical.<div><br></div><div>=
So says Fred Raab, the guru of using low cost mosfets at HF.=C2=A0 =C2=A0It=
 may not be quite so true for LF, but I went to a talk given by Fred many y=
ears ago on this subject, and have seen several papers by him.</div><div><b=
r></div><div>However, my 400 Watt 475kHz amp does have a nice meaty driver =
chip.=C2=A0 =C2=A0<a href=3D"http://www.g4jnt.com/QRO_500kHz_PA_Breadboard.=
pdf">http://www.g4jnt.com/QRO_500kHz_PA_Breadboard.pdf</a></div><div><br></=
div><div>(Yes I know it&#39;s the 500kHz version - somehow never got round =
to updating the write up after retuning for 475kHz)</div><div><br></div><di=
v>Andy=C2=A0 G4JNT=C2=A0<br><div class=3D"gmail_extra"><br><div class=3D"gm=
ail_quote">On 22 April 2018 at 18:23, N1BUG <span dir=3D"ltr">&lt;<a href=
=3D"mailto:paul@n1bug.com" target=3D"_blank">paul@n1bug.com</a>&gt;</span> =
wrote:<br><blockquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8=
ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Since I am cons=
idering an upscaled version of my current class E<br>
amplifier, I put that back on the bench and was taking some<br>
measurements. It uses a single 34N20 FET. In particular I looked at<br>
the gate waveform with the same scope, probes, and settings I&#39;ve<br>
been using with the W1VD deck. I was shocked at how steep the rise<br>
and fall times are and how it seems to &#39;power through&#39; the FET<br>
turn-on anomaly. This stands in stark contrast to the W1VD deck with<br>
its slow gate rise/fall and long hiccup at FET turn on. At least I<br>
know the scope is capable of displaying a &#39;crisp&#39; gate waveform. ;-=
)<br>
<br>
Paul N1BUG<br>
<br>
<br>
<br>
<br>
</blockquote></div><br></div></div></div>

--f403043e1920b71843056a7eec53--