PMA CFA - current feedback power amplifier
This project has started in the beginning of 2016 for the reason that I was interested in a current feedback topology behavior. The current feedback concept is well described in Intersil company application notes. For those who are interested, I recommend to download the AN that I linked. I could hardly add anything more to it.
Amplifier schematics is as follows. The circuit is complete, the only missing parts are a DC servo and 15V stabilizers for the input transistors.
Output devices are robust OnSemi MJL21194/93. Drivers are MJE15030/03. Similarly as in case of my PA4 amplifier, the rugged and reliable amplifier was my goal.
The amplifier is strictly dual-mono, channels do not share any common ground point, so no ground loops are created.
Output DC protection is made with 94A IRFP90N20D MOSFETs, driven through opto-couplers. This was chosen after bad experience with mechanical relay at this position.
Photos of the amplifier
Frequency spectrum at 50Hz/72W/4ohm
THD vs. frequency at 60W and 4ohm load
THD(+N) vs. output voltage, at 1kHz and for 4 ohm, 10 ohm load and no load
Pavel Macura 09/2017