What's with the 2sk3018 MOSFET?

The 2sk3018 MOSFET is an unusual animal. It holds the top 30V spot, in my giant MOSFSET table. Its Crss = 4pF at 5V is the lowest, and its Ron(max) = 8 ohms, with 4V drive, is the highest, giving it the top spot. It's likely the ideal part for my fast programmable current source.

But oops, Rohm says it's NRND. However, it's 2nd sourced by MCC, and Invac and HTsemi. And Kexin, distributed by LCSC.

Whoa, five different sources! Is / was this a jellybean? What are / were its big applications? Anybody hear of it?

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 Thanks, 
    - Win
Reply to
Winfield Hill
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which will run cascode into a HV MOSFET.

More claims to fame: specified for 2.5V gate drive, small SC-70 package, $0.05 from Future. And a sixth manufacturer!!, Changjiang, also stocked and sold by LCSC.

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 Thanks, 
    - Win
Reply to
Winfield Hill

Price, 1.5 cents.

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 Thanks, 
    - Win
Reply to
Winfield Hill

HV cascodes can have some interesting hazards when they turn off fast. You can blow out the gate of the top fet, or the drain of the little one below. An analog current controller isn't so scary as a fast switch.

We considered a GaN+SiC cascode for fast HV pulsing but decided it was better to just build a monster gate driver for the SiC.

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John Larkin         Highland Technology, Inc 

lunatic fringe electronics
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Reply to
John Larkin

Sure, but easily handled with a gate-source TVS, e.g. see Figures 3x.56 and 4x.147 in my x-Chapter handouts.

I haven't seen trouble with cascode MOSFETs, even fast switched ones, but worry about HV supply being suddenly shorted, or applied.

I've been using Diodes' D1213A-01, with a 5A 8/20μs pulse rating, 1.2 pF, in SOD323 package. Happy to spend more capacitance on the TVS, for a higher current rating, but haven't found one.

--
 Thanks, 
    - Win
Reply to
Winfield Hill

I thought the whole point of part numbers was that any device that met its specs could get the part number. Other specs may differ certainly, but not those defining ones.

NT

Reply to
tabbypurr

WARNING. Be advised that every manufacturer of a given part (the

2SK3018 in this case) runs their fab differently, and you may find that those particular specs may be WIDELY different - enough to make the part virtually useless.
Reply to
Robert Baer

Or not. Of course, one must fully evaluate a second-source manufacturer's parts, before committing it to manufacturing.

But in the specific case of the 2sk3018, there are several distinguishing features that most of the 2nd-source providers will probably meet:

(1) The high 4-volt Ron spec. This insures a small die, which a manufacturer will cling too, to insure higher profits. It's most important to me, because it goes with very low capacitance. Capacitance is the primary parameter I'll check.

(2) The 2.5-volt logic-drive capability. Along with low cost, and the tiny SC70 package, this is probably the spec that's most responsible for the popularity of this part. It's not important to me, but may help to insure interchangeability.

The very existance of these alternate sources, each with active stocking distributors, helps to ameliorate Rohm's NRND. I've also ordered 100 of the MCC parts, to evaluate with Rohm. Maybe I'll also order strips of Changjiang and Kexin parts from LCSC, they're dirt cheap. A full 3000-piece reel of Changjiang's part is $40.

--
 Thanks, 
    - Win
Reply to
Winfield Hill

I've found wide variation in switching speed on 2N7002s and BSS123s. We sole-source spec the Fairchild parts. And hope they don't change.

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John Larkin         Highland Technology, Inc 

lunatic fringe electronics
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Reply to
John Larkin

But now that Fairchild is part of ON Semi, and ON Semi has conglomerated pretty much everything, how can you be sure that you won't get the ON Semi version of the 2N7002? You should order a lifetime supply. They're not very expensive.

--
 Thanks, 
    - Win
Reply to
Winfield Hill

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