Heatsink for DC electronic load

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BJTs are a very good option for a current sink, under the following conditions:

- required minimal compliance voltage is >2 V
- required currents are not very high (which would lead to a lot of control current and power)
- note second breakdown at higher Uce. It gives similar limits to DC operation to BJTs as the Spirito effect gives to FETs.

- not planning to go below 2.5-3V
- up to 2A per transistor
- not going to exceed SOA, MCU will adjust max current depending on the voltage to keep it within the SOA. I know more about BJTs than I know about MOSFETs

After I do some math to see if I don't exceed the junction temperature I'll know how many devices I need for a 100W module.

See my teardown of a 1200W 240A that uses MOSFETS, posted it today in the test equipment board.

Nice! 37.5W/MOSFET (1200W/32). Using IRFP250N which is what I was planning to use. It seems they might be able to survive 40W continuous each in my design, although 50W is kind of pushing it. Thing is there'll be one temperature sensor for each MOSFET to measure case temperature and I've got only 8 I²C addresses available which means a max of 4 modules per bus...

What do you think? Some thermal calculations can be found here.