DC Protection for the IGBT Power Amp

Some time ago, the author built a copy of the IGBT Power Amp, a final amplifier design described in the June 1995 issue of Elektor Electronics that has since become a classic. The sound quality provided by the amplifier was more than superb, but it was evident that the output transistors became quite hot during full-power testing (at 140 W). This is not uncommon, of course, but it set an alarm bell ringing, and it was deemed a good idea to at least add DC protection to safeguard the (expensive) amplifier and equally expensive speakers.