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Date: Fri, 8 Jan 2016 21:45:23 +0000
Message-ID: <CAA8k23T6k1D1xssvY0wNeLik8JxKcYPaTcG9=OUZ6TMm+Zz2YA@mail.gmail.com>
From: Andy Talbot <andy.g4jnt@gmail.com>
To: rsgb_lf_group@blacksheep.org, rsgb_lf_group@yahoogroups.co.uk
Subject: LF: Linear Amp for LF
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Are there any proven reliably designed LF amplifier designs power
amplifiers  for 137 / 475?   Wideband, covering both ideally    Rated for
at least 300 Watts output, and ideally a lot more.

I saw G3YXM's low-HF design, and it looks promising for low frequency use,
but he appears to have not gone that way and went for a switchmode version
at LF/MF

Of course, I could just redesign that, or something similar, using suitable
ferrite and a bit of feedback ,but it would be nice to avoid reinventing
too many wheels.

Using switching MOSFETs as linear amps still doesn't feel quite right, but
enough people seem have managed it now (including my own design for a low
power one) that it looks a sound-enough route to follow up.    The one
thing that does bother me about the technique is bias compensation with
temperature.   It is really asking for active bias control, but in a
class-B or -AB design, where bias just affects standing current, that gets
more-than a bit tricky as a concept.

Andy  G4JNT

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<div dir=3D"ltr">Are there any proven reliably designed LF amplifier design=
s power amplifiers=C2=A0=C2=A0for 137 / 475? =C2=A0 Wideband, covering both=
 ideally =C2=A0 =C2=A0Rated for at least 300 Watts output, and ideally a lo=
t more.<div><br></div><div>I saw G3YXM&#39;s low-HF design, and it looks pr=
omising for low frequency use, but he appears to have not gone that way and=
 went for a switchmode version at LF/MF</div><div><br></div><div>Of course,=
 I could just redesign that, or something similar, using suitable ferrite a=
nd a bit of feedback ,but it would be nice to avoid reinventing too many wh=
eels.</div><div><br></div><div>Using switching MOSFETs as linear amps still=
 doesn&#39;t feel quite right, but enough people seem have managed it now (=
including my own design for a low power one) that it looks a sound-enough r=
oute to follow up. =C2=A0 =C2=A0The one thing that does bother me about the=
 technique is bias compensation with temperature. =C2=A0 It is really askin=
g for active bias control, but in a class-B or -AB design, where bias just =
affects standing current, that gets more-than a bit tricky as a concept.</d=
iv><div><br></div><div>Andy =C2=A0G4JNT</div></div>

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