Completely homebrew cheap MOSFET amplifier 300W

[mw0uzo]

Beyond matching the transistors from the same batch, I was concerned about matching the phase inputs to the transistors as well. I am not sure what the schematic looks like on this thing, but the phase delays that occur will naturally be more obvious at the higher frequencies.

I don't know. It's not really usable above 18Mhz. I have been trying to increase the frequency response but not got further than that. Any tips would be most welcome!!

Is it Linear? If so, is it class E?

Its class AB, linearity seems to be ok - it transmits SSB nice and clean with no splatter :)

[ab1ga]

I don't know. It's not really usable above 18Mhz. I have been trying to increase the frequency response but not got further than that. Any tips would be most welcome!!

The IRF MOSFETS were intended for use in switching applications like motor control or power supplies, where operating frequencies are low. Also, it was important to keep the channel resistance low when on to minimize waste heat, which limits lifetime and requires expensive heat sinking or a larger package design.

The high-current capability required a fairly wide channel, even for VMOS, TMOS, etc. designs. Put a metal gate across that, and you have a nice capacitor. That capacitance forms an RC circuit with any gate series resistance which limits frequency response. A related parameter, gate charge, provides a useful guide. The bigger it is, the harder it is to move it back and forth to vary channel conductance. The larger the gate charge, the higher the gate current (i.e., drive) required to modulate the channel conductance.

73,