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From: liz@poppyrecords.invalid.invalid (Liz Tuddenham)
Newsgroups: sci.electronics.design
Subject: Re: dumping a lot of heat
Date: Sun, 8 Dec 2024 17:34:56 +0000
Organization: Poppy Records
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john larkin <JL@gct.com> wrote:

> On Sun, 8 Dec 2024 16:36:25 +0000, liz@poppyrecords.invalid.invalid
> (Liz Tuddenham) wrote:
> 
> >Jan Panteltje <alien@comet.invalid> wrote:
> >
> >> On a sunny day (Sun, 8 Dec 2024 13:33:39 +0000) it happened
> >> liz@poppyrecords.invalid.invalid (Liz Tuddenham) wrote in
> >> <1r490yz.1xraied16vto76N%liz@poppyrecords.invalid.invalid>:
> >> 
> >> >john larkin <JL@gct.com> wrote:
> >
> >[...]>RL
> >> >> 
> >> >> Tubes were awful. Still are.
> >> >
> >> >The techniques for designing with them are quite different from
> >> >transistors and ICs, you have to think a different way; they aren't just
> >> >poor transistors, they have a different lifestyle altogether.  They also
> >> >have some advantages over semiconductors:
> >> >
> >> >1)  Withstanding short term overloads without damage.
> >> 
> >> Thermal overloads depend on teh heatsink.
> >
> >Only slow overloads.  Fast ones depend on the thermal time constant of
> >the bit being heated by the overload.  Some time later the energy
> >reaches the heat sink but but then the damage is done.
> >
> >I've just accidentally mixed up the anode and grid pins of one of the
> >triodes in an ECC91.  It drew about 100 mA for a few seconds with no
> >damage.  That's equivalent to mixing up the Base and Collector
> >connections on a transistor and subjecting the Base-Emitter junction to
> >about 10 times the rated maximum Collector current.  How many
> >transistors would survive that, even with the biggest heatsink
> >available?
> 
> Mosfet data sheets usually have SOAR curves.
> 
> IXFH400N075T2 is rated for 1000 amps and 1000 watts (with astericks)
> and 30 kilowatts for 25 uSec. 

Into the gate?

-- 
~ Liz Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk