Space Varmint
New Member
Thought you guys might to look at this new power amp I just finished up. It's a 200 watter for the HF bands. The finals are 2SC2879's. They are an up grade from some Motorola transistor that is 100 watts. I have heard stories that you can get 150 watts from each. The drivers are MRF475's and the other TO220 packages in the center of the board are LM317's for the bias to the class A linear finals. Anyway I wanted to share this because of course I'm always gonna look for sample designs and could not find anything that looked like a real push-pull at these frequencies and or power levels. I found one or two designs that used an LR network to shift the phase but this would be a poor broadband amplifier because the inductance would change with frequency so I drafted this up off the cuff and had to do very little to change it once put together. All cores are Amidon number 43 mix. The signal paths use balun cores and the toroid cores are just chokes used to clean up the power bus along with various size filter caps. I put .01uf caps all around the board from power to ground.
edit*
I thought I should mention the symbols for the final power transistors. They are custom and I had to do them with two emitters in Eagle or it would not pick them both up in the board Gerber file. The finals are SOE (Silicon Opposed Emitter) which are the big round pill looking transistors with gold plated fins and it has 4 of these flat fins because two of them are emitters which are usually grounded and so they make a nice ground plane when soldered to the PC board ground plane. You always know the pin configuration because the collector is cut at a slant and the opposing emitter means they are straight across from each other so that leaves the base across from the collector.
edit*
I thought I should mention the symbols for the final power transistors. They are custom and I had to do them with two emitters in Eagle or it would not pick them both up in the board Gerber file. The finals are SOE (Silicon Opposed Emitter) which are the big round pill looking transistors with gold plated fins and it has 4 of these flat fins because two of them are emitters which are usually grounded and so they make a nice ground plane when soldered to the PC board ground plane. You always know the pin configuration because the collector is cut at a slant and the opposing emitter means they are straight across from each other so that leaves the base across from the collector.
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