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| Example of why people say you sholdn't use MOSFETs in parrallel as dummy load |
| (1/4) > >> |
| SpottedDick:
Nothing much to say here. Six MOSFETs in parallel as a dummy load. Due to variance you can see two in particular are taking most of the load. This was just before I put the heat sink on. (I already had the thermal paste on them, otherwise I would have used back tape to make the image a bit more accurate, but it gets the idea across). |
| ebclr:
Some small resistor will help to equalize |
| TimFox:
--- Quote from: ebclr on June 18, 2022, 11:42:33 pm ---Some small resistor will help to equalize --- End quote --- Best to install equalization resistors in series with the source terminal of each device. |
| fourfathom:
The source resistors are a good idea, but remember that the MOSFET RDSON has a positive tempco, so the imbalance you are seeing will not be as bad when the transistors are all sharing the same heatsink. |
| nctnico:
--- Quote from: ebclr on June 18, 2022, 11:42:33 pm ---Some small resistor will help to equalize --- End quote --- Not small. You'll need a considerable resistor value to equalize the currents. MOSFETs have a large variation. And you'll want to use MOSFETs for analog (audio amplifier) applications in order to have a reasonable SOA at DC. I very much prefer to use transistors mainly because the collector already acts as a current sink by definition. At DC you only need to have a slow loop to compensate for temperature drift effects. |
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