Project 11 is a descendant of Project 5, which uses standard building blocks of a conventional power amplifier circuit with power MOSFETS output stage. The circuit is as simple as it can get to build an audio power amplifier, but reproduces excellent audio fidelity. Project 11 was the result of revisiting the original circuit and replacing the power MOSFETs and drivers with less expensive and readily available parts while still retaining its sound quality reproduction.

Project 11 uses the same schematic diagram as in Project 5 except for the T0220 version. The T0220 version have 3 pairs of power MOSFETs. I have revised Project 5’s PCB layout to match with the change in the power MOSFETs' pinouts for both T0247 and T0220 versions. D1 was also replaced with a Fairchild Semiconductors’ FDH444 which has a forward voltage of 1.2V at 300mA and readily available during the time I built the models for both versions. The power MOSFETs for T0220 version are IRF640 and IRF9640 and for the T0247 version FQA36P15 and FQA28N15.

The test procedure for this project is identical with Project 5. In both T0220 and T0247 versions the idle current must be adjusted at 10mA. The idle current is measured by removing the F+ fuse and replacing it with a milliammeter. Readjust the idle current after a warm up period of about 30 minutes.  As usual the schematic diagram for T0220 version, Project11 BOM and PCB layouts of both versions are provided for free, as is, no warranty. Enjoy!

Schematic Diagram of Project 11 - T0220 package version.

 

Bottom Copper Layer - T0220 Version of Project 11

 

Silkscreen Parts Placement Layer - T0220 Version of Project 11

 

Bottom Copper Layer - T0247 Version of Project 11

Silkscreen Parts Placement Layer - T0247 Version of Project 11