SM0VPO Half Watt Amp

This amp comes from Harry Lythall who has a web page at
SM0VPO Half watt amp

I built built one myself and made a couple minor modifications to stop
the clipping I had seen when I built mine.

This is a cool little amplifier. It uses all 2n2222's in a parallel push-pull two state layout.
It has about 30 dB of gain and can be driven from oscillator levels. (-4dBm). I had to
add about 16dB of attenuation to the output of my MFJ analyzer to keep it from clipping
and then got between a quarter and a half watt thru the HF range.

I changed the biasing resistors of the input amplifier to keep the preamp from clipping
at drive levels necessary to drive the push-pull amps up 250-500 mW. I determined
the values of the biasing resistors by fiddling with LTSpice until I was able to drive the
preamp with 400mVPP without clipping and still get decent drive to the final transistors.

The output is pretty clean - the scope wave forms look sinusoidal - but I would still
use a low pass filter with it unless you run it at low drive levels. ( a difference of a few
dB of drive made a big difference in the level of the second harmonic.)

Here is the LTSpice file
SM0VPO half watt amp LTSpice file

Here is the Schematic
SM0VPO half watt amp Schematic

Here is the Photo
SM0VPO half watt amp Photo