Dear Mal, LF Group,
> Hi all
> Class D and E amplifiers are supposed to give around 80/90 % efficiency.
Has
> anyone actually achieved these figures. It seems anything above 60% is
hard
> to arrive at using normal coils/capacitors.
>
> 73 de Mal/G3KEV
>
Certainly you should be getting better than 80% for a reasonable class D or
E design at LF or MF. I find about 90% is typical for a "good" design - it
is actually quite hard to get an accurate figure due to the small difference
between DC input and RF output powers.
In my designs I have used silver-mica or polypropylene capacitors, which
have very low losses at these frequencies. For inductors, I have used
air-wound coils and Micrometals -2 mix iron-dust toroid cores - the rule
here is if doesen't get excessively hot with the key down, the power loss is
probably ok! For most class D and E designs, which have quite low loaded-Q
tank circuits (<5, say) an inductor Q of 100 or more is probably adequate
and fairly easy to achieve. If you want to use a high loaded-Q tank circuit,
it might be another story...
Cheers, Jim Moritz
73 de M0BMU
|
