[AMRadio] Can you have Class D and Class E tube amps?


Alan Victor amvictor at ncsu.edu
Tue Dec 27 11:19:44 EST 2016


(sent to Chris in an earlier mail, did not post to the group)...

Hi Chris. I have investigated both D and E designs based on FET, MOSFET,
HEMT devices and there is nothing sacred about the designs which forces
them to be linked to solid state units. The success of these designs is
based on the ability to provide properly shaped current and voltage
waveforms across the device and at the load. As one figure of merit,  the
FT or FMAX of the device applied to FETs can be applied to tubes and in a
similar manner compute a gain/frequency  figure of merit. Bottom line high
gain at high frequency compared to the operating frequency is a place to
start. So a tube with significant gain at 136 MHz would be a good start.

Alan W4AMV

On Tue, Dec 27, 2016 at 11:15 AM, Jim Candela <jcandela at prodigy.net> wrote:

> The classes of operation, a,b,c,d,e, etc. can be applied to solid state or
> tubes. The Retro75 and Retro40 transceivers made by Small Wonder labs used
> a class D RF output stage using a power FET followed by a LPF. Both class D
> and E can use sine wave drive, or preferably a single polarity pulse that
> is about 40-45% the width of a half cycle. The output circuit for class D
> is a LPF, and for class E, it is a resonant tank. Class E is usually a
> little more efficient, but class D is simpler in that no tuning is required.
> For 137Khz, if the old 1 watt DC input rule is still in effect, you want
> the highest efficiency possible. Therefore class E would be desired. Should
> be able to get 95% or higher efficiency.
>
> JimWd5JKO
>
>
>     On Tuesday, December 27, 2016 8:32 AM, Rob Atkinson <
> ranchorobbo at gmail.com> wrote:
>
>
>  That's right, Bob in Penn Yan and the other guy is I think John K5PRO?
>  I think he has one.
>
> Rob
> K5UJ
>
> On Tue, Dec 27, 2016 at 6:16 AM, Mike Sawyer <w3slk at verizon.net> wrote:
> > I think W2ZM uses one of those on 160M frequently. I remember seeing
> one. If
> > memory serves me the plate is actually kept at 0VDC potential and the
> > cathode is where the HV is applied. Audio input is fed via fiber optic to
> > maintain isolation(?). I'm just going from a one-time explanation from 25
> > years ago.
> >
> > Mod-U-Lator,
> > Mike(y)/W3SLK
> >
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