Reply by Piotr Wyderski July 20, 20192019-07-20
Winfield Hill wrote:

> OK, depletion mode wasn't mentioned in the saga > section, but it was plenty elsewhere, and cross- > referenced.
It is impossible to overpraise these niche parts. Could you please just mention that their high-power variants do exist and let the reader google the details? ;-)
> Piotr, have you used it for anything interesting?
Once upon a time I badly wanted to use a pair of them as an AC current limiter, but they turned out to be expensive unobtainium back then. They would have had many advantages (e.g. they require no external power to start operation, while the enhancement-mode approach has the usual chicken-and-egg problem), but due to the empty stock I had to chose a more standard path. I have 3 successfull applications you might find interesting enough: 1. Normally closed micropower "bleeder resistor" equivalent based on an IXTP08N100D2. This is to discharge the bus capacitor charged to 600V by a PFC stage. The current is set to the max level allowed by the thermal capabilities of TO220 under continuous operation. If the powered device (an FPGA, to be specific) fails for some reason, the bleeder steps in, otherwise it powers a tiny RF transformer wound on a 6mm core with a 1MHz square wave that produces the negative gate voltage, turning the bleeder off. 2. Active clamp transistor in a forward SMPS which operated at voltage just within the allowed VGS ratings. Extremely simple gate drive, the same PWM signal used to drive the main switch and the depletion-mode FET. Maybe patentable, I don't really care. 3. Phase-sensitive AC zero-crossing detector made of two LND150 and a coupled choke wound on an amorphic metal core. This is basically an AC current source powering a coil with 1mA, so nothing spectacular happens there. Unless the polarity reverses and the "current source" is no longer capable of providing constant current. Then the magnetic field collapses and bang! -- there is a very narrow voltage spike indicating the zero crossing. The second coil wound on the same core transforms this rapidly changing magnetic field into a desired voltage spike, say +/-2.5V. If the polarity information is a problem, just add a full-wave rectifier to the output. The choke can be wound with a TIW, so a substantial insulation level can be achieved. The LND150s in TO92 can be put together along the flat part of the casing and then inserted into the hole of the 12.7mm core. Then the entire isolated zero crossing detector would be composed of just 4 parts (2x the FET, a 1mA-setting shared source resistor and the "transformer" can fit within a circle of diameter ~14mm. Best regards, Piotr
Reply by Phil Hobbs July 20, 20192019-07-20
On 7/19/19 5:53 PM, Winfield Hill wrote:
> John Larkin wrote... >> >> On 19 Jul 2019 09:56:28 -0700, Winfield Hill <winfieldhill@yahoo.com> >> wrote: >> >>> A new section from the AoE x-Chapters book, >>> for you to read, enjoy, and make comments. >>> >>> A 30-Year MOSFET Saga, The next 15 years, >>> and Four kinds of power MOSFETs. >>> >>> https://www.dropbox.com/s/0qh8dxgielrkqvq/chap-3x.11_MOSFET-saga_2019-07-19.pdf?dl=0 >> >> Who was it that made medium-power VMOS fets >> before the IRF things? > > I think, Siliconix. I have an old Siliconix > databook someplace, couldn't locate it just now. > Hardcover Siliconix MOSPOWER Applicatiosns book > is dated 1984, features IRF part numbers for > the more beefy parts.
Siliconix it was. I went to a conference talk by one of their apps guys in early 1982. They were really emphasizing the (then) good current sharing of parallelled FETs vs. bipolars. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
Reply by Winfield Hill July 20, 20192019-07-20
Piotr Wyderski wrote...
> >Winfield Hill wrote: > >> A new section from the AoE x-Chapters book, >> for you to read, enjoy, and make comments. > > Very interesting, but no depletion-mode power > MOSFET like the IXTH20N50D is even mentioned? > That's a pity.
OK, depletion mode wasn't mentioned in the saga section, but it was plenty elsewhere, and cross- referenced. It's also reasonably-well covered in the main book, with Table 3.6 as well, where the IXTH20N50D is at the bottom of the table; the biggest, baddest part, the top of the heap. Piotr, have you used it for anything interesting? -- Thanks, - Win
Reply by Piotr Wyderski July 20, 20192019-07-20
Winfield Hill wrote:

> A new section from the AoE x-Chapters book, > for you to read, enjoy, and make comments.
Very interesting, but no depletion-mode power MOSFET like the IXTH20N50D is even mentioned? That's a pity. Best regards, Piotr
Reply by John Larkin July 20, 20192019-07-20
On Fri, 19 Jul 2019 19:46:52 -0400, Martin Riddle
<martin_ridd@verizon.net> wrote:

>On 19 Jul 2019 09:56:28 -0700, Winfield Hill <winfieldhill@yahoo.com> >wrote: > >> A new section from the AoE x-Chapters book, >> for you to read, enjoy, and make comments. >> >> A 30-Year MOSFET Saga, The next 15 years, >> and Four kinds of power MOSFETs. >> >>https://www.dropbox.com/s/0qh8dxgielrkqvq/chap-3x.11_MOSFET-saga_2019-07-19.pdf?dl=0 > >No mention of RF Mosfets? > >New radio designs are moving to Mosfet PA's. > >Cheers
GaN fets are wildly better than any mos parts. -- John Larkin Highland Technology, Inc lunatic fringe electronics
Reply by John Larkin July 20, 20192019-07-20
On 19 Jul 2019 14:53:46 -0700, Winfield Hill <winfieldhill@yahoo.com>
wrote:

>John Larkin wrote... >> >>On 19 Jul 2019 09:56:28 -0700, Winfield Hill <winfieldhill@yahoo.com> >>wrote: >> >>> A new section from the AoE x-Chapters book, >>> for you to read, enjoy, and make comments. >>> >>> A 30-Year MOSFET Saga, The next 15 years, >>> and Four kinds of power MOSFETs. >>> >>>https://www.dropbox.com/s/0qh8dxgielrkqvq/chap-3x.11_MOSFET-saga_2019-07-19.pdf?dl=0 >> >> Who was it that made medium-power VMOS fets >> before the IRF things? > > I think, Siliconix. I have an old Siliconix > databook someplace, couldn't locate it just now. > Hardcover Siliconix MOSPOWER Applicatiosns book > is dated 1984, features IRF part numbers for > the more beefy parts.
I think VMOS was a v-shaped notch etched through n-p-n layers, with the gate deposited in the notch, so the current flow was vertical. IR extended that idea to many cells, like an IC. That was the hexfet, with 6-sided cells. Then as I recall Motorola or someone did the same thing, but with square cells. -- John Larkin Highland Technology, Inc lunatic fringe electronics
Reply by Cursitor Doom July 20, 20192019-07-20
On Fri, 19 Jul 2019 19:04:49 -0700, Winfield Hill wrote:

> Yep, that's beyond the scope of our book.
In detail I've no doubt it would be! But just a summary overview in passing wouldn't hurt, shirley? -- This message may be freely reproduced without limit or charge only via the Usenet protocol. Reproduction in whole or part through other protocols, whether for profit or not, is conditional upon a charge of GBP10.00 per reproduction. Publication in this manner via non-Usenet protocols constitutes acceptance of this condition.
Reply by boB July 20, 20192019-07-20
On Fri, 19 Jul 2019 19:46:52 -0400, Martin Riddle
<martin_ridd@verizon.net> wrote:

>On 19 Jul 2019 09:56:28 -0700, Winfield Hill <winfieldhill@yahoo.com> >wrote: > >> A new section from the AoE x-Chapters book, >> for you to read, enjoy, and make comments. >> >> A 30-Year MOSFET Saga, The next 15 years, >> and Four kinds of power MOSFETs. >> >>https://www.dropbox.com/s/0qh8dxgielrkqvq/chap-3x.11_MOSFET-saga_2019-07-19.pdf?dl=0 > >No mention of RF Mosfets? > >New radio designs are moving to Mosfet PA's. > >Cheers
DMOS I think are those RF ones. Siliconix and I think Toshiba both made early VMOS FETs I think. Tried them in a class AB audio amplifier in the late 1970s when they were first available. Worked OK. Haffler made amps from those early FETs too.
Reply by Winfield Hill July 19, 20192019-07-19
Cursitor Doom wrote...
> > On Fri, 19 Jul 2019 19:46:52 -0400, Martin Riddle wrote: > >> New radio designs are moving to Mosfet PA's. > > THAT would be interesting. How about it, Win?
Yep, that's beyond the scope of our book. -- Thanks, - Win
Reply by Cursitor Doom July 19, 20192019-07-19
On Fri, 19 Jul 2019 19:46:52 -0400, Martin Riddle wrote:

> New radio designs are moving to Mosfet PA's.
THAT would be interesting. How about it, Win?