Because of the high maintenance needed to monitor and filter spammers from the RF Cafe Forums, I decided that it would
be best to just archive the pages to make all the good information posted in the past available for review. It is unfortunate
that the scumbags of the world ruin an otherwise useful venue for people wanting to exchanged useful ideas and views.
It seems that the more formal social media like Facebook pretty much dominate this kind of venue anymore anyway, so if
you would like to post something on RF Cafe's
page, please do.
Below are all of the forum threads, including all
the responses to the original posts.
Post subject: Nonlinear wideband (power) amplifier Posted: Tue May 16, 2006 5:21 am
Joined: Tue Dec 13, 2005 2:42 am
Location: Czech Rep.
I just want
to ask you.
I would like to build a wideband 'power' amplifier working let's say in C Class. (I'm speaking
about 150-450MHz band approximately, 0.5-1W out.)
Does the nonlinear wideband amplifier even exists?
...Because I haven't found anything about it.
Do you have some design recommendation?
Thank you for
Post subject: Broadband Class C amplifierPosted: Tue May 16,
2006 6:33 pm
Joined: Wed Feb 22, 2006 3:51 pm
amplifiers are unfortunately inherently not wideband. Here's why
Class C amplifiers are defined by having a
conduction angle of less than 180 degrees. This results in a pulse of current being applied to the output network,
which resonates at the operating frequency. This resonance reduces the harmonics which are necessarily generated
with less than 180 degrees conduction angle. The Q may vary, but the resonance is critical to the proper operation
of the circuit.
Because the current pulse is not symmetrical, both even and odd harmonics are generated. So
in your specifications, a 150 MHz input signal would result in 300 and 450 MHz spurious signals, which would not
be filtered out - not so good.