Yes, 12 ohms is nice. But it'd take Vgs about -2.25V to limit the current to 25mA, so R4 = 91 ohms. That's 115 ohms total, 1.4nV, not too much worse than 87 ohms. It's a 300V part, DN2530N3 in convenient TO-92 package, and the DN2530N8 is a 1.6-watt SOT-89 SMT package.
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Thanks,
- Win
We use the SOT-89.
Looks good for 3 watts, properly copper-poured.
It makes a nice linear cap bleeder. Saves time.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
Hey, John, 3W very nice, yes, but 15 square inches!?! How about only 1 square inch, which is still a lot to give up. Is that the 1.6W spec?
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Thanks,
- Win
One could via down to an internal plane and/or a copper patch on the bottom of the board.
I wouldn't actually use it at 3 watts, but the specified 1.6 looks conservative.
More copper area has diminishing returns, due to thermal spreading resistance. An infinite sheet doesn't have zero theta. The patch area of the device matters a lot. Vias to other spreading layers helps. 2 oz copper would cut theta a lot.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
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