4 Pairs of VMOS output stage for the modular high end audio amplifier

Project presentation

Abstract

The amplifier output stage presented here is part of my modular audio amplifier system. It is designed to be equipped with four pairs of vertical MOSFETs in TO-247 package, for example IRFP240 and IRFP9240. Of course, different pin compatible transistors can be used as well.

This output stage is basically like the four pairs BJT output stage, just with different transistors and some minor adaptions.

Since I also have designed an output stage featuring six pairs of vertical MOSFETs, I likely never will build the one presented here. For now, this is merely a study.

Schematic

Assembly

The mounting holes fit on the 20mm grid, the whole modular system is based on. The transistors in TO-247 package can be mounted to the 20mm grid as well and this results in a very compact placement of the circuitry. The modules overall dimension is smaller by only one grid unit (20mm) than the BJT output stage module or the MOSFET output stage with six pairs of transistors.

Summary

The higher safe operating area of the vertical MOSFETs allows much higher output power than the 4 pair BJT output stage allows. For even higher power, I have designed an output stage featuring six pairs of vertical MOSFETs.