TO220--thin leads--high current--How?
in [Design]
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From: MooseFET on 4 May 2010 23:07 On May 3, 11:28 pm, "JosephKK"<quiettechb...(a)yahoo.com> wrote: > On Mon, 3 May 2010 18:09:56 -0700 (PDT), MooseFET <kensm...(a)rahul.net> > wrote: > > > > >On May 3, 10:24 am, "Tim Williams" <tmoran...(a)charter.net> wrote: > >> "MooseFET" <kensm...(a)rahul.net> wrote in message > > >>news:a255d645-99e3-4207-8aad-dbe3d49c2988(a)h20g2000prn.googlegroups.com.... > > >> > There is some poorly documented impedance between the gate leg > >> > and the actual controlling gate element. > > >> In other words, gate spreading resistance. And maybe some inductance, and > >> other squirrelies, depending on how detailed you want to get. More > >> important also is the source lead inductance (which is sometimes specified > >> at 5nH or so). > > >> I get the impression that spreading resistance has dropped over the years. > >> Back in the day, you didn't see FETs spec'd for very impressive rise/fall > >> times. But they also used fairly large Rg's, so is it just that they didn't > >> try? > > >Way back when there was little point in going below a 20 Ohm gate > >driver. > >Today that is very much no longer the case. > > >The funny thing is that the Siliconix parts of the past had low gate > >resistance can worked as very nice class D RF stages at 16MHz. I > >could > >get a couple of watts out of a VN88 with good efficiency. > > Class D or class S? Really class S at 16MHz. The "D" ness was a duty cycle control to dial the power up and down a little. I was experimenting with a servo regulated discharge lamp idea.
From: JosephKK on 5 May 2010 00:34 On Tue, 04 May 2010 09:44:00 -0700, John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >On Mon, 03 May 2010 22:59:36 -0700, >"JosephKK"<quiettechblue(a)yahoo.com> wrote: > >>On Sun, 02 May 2010 14:45:25 -0700, John Larkin >><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >> >>>On Sun, 2 May 2010 14:18:25 -0700 (PDT), "oparr(a)hotmail.com" >>><oparr(a)hotmail.com> wrote: >>> >>>>>Be safe, don't buy IR. >>>> >>>>My MOSFETs of choice and I have no "Once bitten, twice shy" rants. >>>> >>>>On May 2, 3:44 pm, John Larkin wrote: >>>>> >>> >>>I've never been "bitten" by IR specs, because they looked absurd to me >>>at first glance. >>> >>>Do I sound shy to you? >>> >>>John >> >>Jerk. See the placement of the quotes in the original. > >I think the quotes indicate that the writer didn't originate the text. >But even cliches have meaning. > >Tell us about your recent design experiences with power mosfets. Or >even your ancient design experiences with power mosfets. > >John > > Ancient but it was fun at the time. Had to produce current pulses and ship them into a vacuum chamber and be able to prove their shape. The smaller current pulses were 20 and 30 A for 75 and 100 microseconds. Not too bad. The higher current pulses were 120 and 300 A for 900 and 300 nanoseconds respectively. Those were somewhat challenging back then (25+ years ago). Car batteries worked pretty well for the bulk source. Wound some hefty current transformers for that one too. Different fuses (the DUT) for each test case.
From: JosephKK on 5 May 2010 00:45 On Tue, 04 May 2010 08:33:59 -0700, John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >On Tue, 4 May 2010 09:22:00 -0500, "Tim Williams" ><tmoranwms(a)charter.net> wrote: > >>"JosephKK" <quiettechblue(a)yahoo.com> wrote in message >>news:1gdvt5hg195np1oo7f3kj4t72ir37q1btt(a)4ax.com... >>> IF you can bother to read the datasheet and app notes correctly they use >>> an _infinite heat sink_ powered by large flow of LN2. They know the >>> spec is bullshit, but the marketeers (who will never know anything of >>> reality) insist on the specmanship games. >> >>That wouldn't work. >>http://en.wikipedia.org/wiki/Critical_heat_flux >> >>Tim > >Where can I buy one of those infinite heat sinks? The scrap metal >value alone would be ... calculates furiously ... infinite! > >But where would I store it? I already have an almost-infinite heat >sink > >ftp://jjlarkin.lmi.net/Infinite_Sheet.jpg > >and it's a nuisance already. > > >John > Tim, John, Read the relevant App Notes, etc. Look at the pictures. It is possible to do interesting things at 77 K. And vaporizing many SCF of LN2 per second transports a lot of heat.
From: JosephKK on 5 May 2010 00:48 On Tue, 04 May 2010 07:05:08 -0700, John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >On Mon, 03 May 2010 23:06:40 -0700, >"JosephKK"<quiettechblue(a)yahoo.com> wrote: > >>On Sun, 2 May 2010 14:12:13 -0700 (PDT), "oparr(a)hotmail.com" >><oparr(a)hotmail.com> wrote: >> >>>> 429?!!! The most ludicrous IR claim I've seen for a D2PAK was 340. >>> >>>The spec states that 429A is; >>> >>>"Calculated continuous current based on maximum allowable junction >>>temperature. Package limitation current is 160A." >>> >>>The only thing that makes sense is the packaged limited current IMO. >>>This D2PAK has 6 source leads and the entire tab is the drain lead. >>> >>>On May 2, 3:46 pm, John Larkin wrote: >>>> >> >>Again an infinite heatsink driven by copious amounts of LN2. > >Gp they use LN2? The appnote cited here said "nucleated boiling >liquid." > >John Are you proposing that LN2 cannot boil in the normal (nucleate) way?
From: JW on 5 May 2010 06:02
On Tue, 04 May 2010 08:33:59 -0700 John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote in Message id: <n9f0u5ptvtt5ucebjtj721oq7esku70lr0(a)4ax.com>: >On Tue, 4 May 2010 09:22:00 -0500, "Tim Williams" ><tmoranwms(a)charter.net> wrote: > >>"JosephKK" <quiettechblue(a)yahoo.com> wrote in message >>news:1gdvt5hg195np1oo7f3kj4t72ir37q1btt(a)4ax.com... >>> IF you can bother to read the datasheet and app notes correctly they use >>> an _infinite heat sink_ powered by large flow of LN2. They know the >>> spec is bullshit, but the marketeers (who will never know anything of >>> reality) insist on the specmanship games. >> >>That wouldn't work. >>http://en.wikipedia.org/wiki/Critical_heat_flux >> >>Tim > >Where can I buy one of those infinite heat sinks? The scrap metal >value alone would be ... calculates furiously ... infinite! > >But where would I store it? A black hole? (retrieval could be a problem...) |