Has anyone tried these? It is a mosfet module similar looking to a Maplin amp with an L bracket. The main difference is that it uses IRFP240 / 9240 vertical fets. There is a temp compensation thermistor built in. I have two which I bought recently. They seem to work quite good. £30 it costs for the bigger of the two boards which has 4 fets.
The trouble with the Maplin circuit is that it is only suitable for Lateral Mosfets which have a negative thermal coefficient. Using vertical FETS like the IRFP240 etc will need the 1k variable bias adjust pot replacing with a bias transistor mounted on the heatsink, otherwise if used hard, thermal runaway could occur destroying the output transistors.
These modules are still available and I've used several without any issues. As has been said, they are basically the Maplin design but with transistor current source for the differential pair and a NTC thermistor in parallel with the bias resistor.
I've used several in audio applications and also modified a few for DC operation to operate as a servo amplifier and as a piezo actuator driver.
I'm sure the module design would be shot down in some respects but I recommend them.
I've used several in audio applications and also modified a few for DC operation to operate as a servo amplifier and as a piezo actuator driver.
I'm sure the module design would be shot down in some respects but I recommend them.
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