I've done a redesign of the distribution amplifier without transformers or other ferrite (apart of dc filters). This required 2 transistor chains in parallel or 96 mA at 24V / Channel. It runs quite hot but looks like it could work from KHz to 600 MHz+. Harmonics are down 40 dB at 250 MHz/13 dBm including SMPD signal generator and the 54846B scope digitizers. AF decoupling is in again as well as Bruce's base divider caps.
http://www.hoffmann-hochfrequenz.de/downloads/IMG_0499__Q73.jpg I had quite a lot of stability problems in the last stage; it liked to oscillate at 1.5 to 3 GHz. I had to use 33R base stoppers for the pnp transistors and tried a week's evenings with Genesys to get rid of them to no avail. I even tried 0603 base decoupling caps right _through_ the board from the base pad to the ground plane 0.5mm / 20 mil away. There is still a lot to do optimizing the voltage drops per stage and characterizing that thing. Any idea of more harmless pnp wideband transistors with Ptot = 1W? Maybe I could run this with -24V and use more NPNs and the pnp only in the CC stage. The efficiency might be improved with a 10 uH choke from the final collectors to gnd. That could be accomplished without ferrite or at least with a large air gap. regards, Gerhard dk4xp _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.