First go at SMD pcb for 300 watt mosfet amplifier.

The output mosfets are IRFP240/9240.
The rest of the circuit is based on an old Hitachi lateral mosfet application note.
I added a Vbe multiplier and vertical mosfets to the design.
I added some decoupling to the front end and this cuts out any residual hum from the power supply
I was surprised to find I could solder something so small, my hands are shaky at the best of times.
A decent pair of tweezers helps with grips on them.
Some of the components arent spot on but the pcb works OK.
I made the SMD pads are little larger than the component to make it easier to hand solder.
looks good nigel,
i rest my hand against the bench when using the tweezers to place a part, helps with the shaking and alignment. use a 10x jewelers loup for mag/inspection. also 15mil glow core no clean eutectic solder works the best for me.
what are you using for small sig devices, sot-23 pkg I assume. no, it looks like you are using to-92 and thru-hole ecaps in a mixed tech layout.
have you discovered the fairchild fjv992/1845 devices? if you want to go away from to-92
Last edited:
i am sure you have lots of those mpsa parts to use, so why not use them if you have them. to-92 do not take up much room.
fjv992/1845 are 120V devices and really low noise too, great for the input stages, even good for a MM phono amp. that is if you ever decide to use more smt instead of to-92.
i am so near sighted I can read the numbers on a 0603 resistor :)
good luck with your ckt.