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Old 11th March 2015, 12:32 AM   #1
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Default STMicroelectronics SCT20N120 and SCT30N120

I have a good memory and when I saw the datasheets of new Silicon-Carbide Power MOSFETs after opening a link in a Digikey mailing it triggered something. I thought I had seen similar curves in Nelson's FIRST WATT SIT INTRO paper!

I know very little about electronics (blessed are the ignorant!) and have no idea if this MOSFET would be suitable for power amp building. The curves in figure 4 of the datasheets just seemed so similar to those in Nelson's paper (and so different to those of the IRFP240 I looked up for comparison) that I thought this might be interesting.

http://www.st.com/web/en/resource/technical/document/datasheet/DM00118513.pdf
http://www.st.com/web/en/resource/technical/document/datasheet/DM00053079.pdf
http://www.vishay.com/docs/91210/91210.pdf

As you might imagine, I am curious if all those hours of reading threads on diyaudio.com have miraculously resulted in a spark of understanding

So, I would like to ask a question to those who understand these things
Am I right to conclude that with curves like those shown in figure 4 of the datasheet, this MOSFET is more triode than pentode?

Perhaps I will read about someone designing an amp for these (or similar) MOSFETs in the future. If so, it is nice to know I was able to figure out they might be suitable, although I have no real understanding why!

Albert
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Old 11th March 2015, 12:46 AM   #2
Zen Mod is offline Zen Mod  Serbia
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not really

to know that with some certainty , one need graphs in area interesting to us - up to,say, 40-50-60-ish voltage and up to ,say,5-10A max

those expanded graphs ( up to 50-ish amps) are same as you are watching your pc screen from 3cm distance , trying to read ......... and somehow you superglued your forehead to screen

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Old 11th March 2015, 12:58 AM   #3
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Thanks Zen Mod. Back to reading more threads it is for me.There is still much I have to learn!
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Old 11th March 2015, 03:04 AM   #4
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Both ST SiC devices shown here are depletion mode (normally off) mosfets (probably eminently suitable for a "Fake SIT"), but not a SIT by nature (a normally-on depletion mode device with triodish characteristics). Nelson is probably sitting on one of the larger stashes of SiC SITs on the planet.

The emergence of these devices from ST is probably going to put even more price pressure on "premium" vendors like Cree, as ST is notorious (among others) for bombing prices. It remains to be seen whether they can get away with this practice for SiC devices, which are still rather immature and eat up money in fab costs (yield? how many/how bizarre process steps).
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Old 11th March 2015, 06:50 AM   #5
EUVL is offline EUVL  Europe
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> Both ST SiC devices shown here are depletion mode (normally off) mosfets

I would have thought depletion mode is normally ON, not true ?

Depletion and enhancement modes - Wikipedia, the free encyclopedia
http://ww1.microchip.com/downloads/e...%20B060313.pdf

There is no direct association between SiC and SIT.
There are SiC devices which are not SIT, and there are SIT's which are silicon based.
One does not imply the other.

Static induction transistor - Wikipedia, the free encyclopedia
http://www.firstwatt.com/pdf/art_sit_intro.pdf


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Old 11th March 2015, 05:31 PM   #6
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I goofed - I meant enhancement mode. I wish they were depletion mode, they might be more interesting to play with.

Having said that,I still haven't really begun to plumb the possibilities of "fake SITs" using Si enhancement mode devices, or what can be done with the Si depletion mode devices available from folks like Supertex (now part of Microchip) and Ixys. What I need is more time, not more playthings.

Since the SiC mosfet prices have come way, way down, I'll eventually end up buying some SiC mosfets to investigate how well they work in "fake SIT" mode -( read partial feedback to impart "triode-like" characteristics). The voltage ratings make them attractive for use at vacuum tube voltages. However, I'll need to finish quite a few other works in progress before I even think of getting around to something like that.
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Old 20th April 2015, 12:36 AM   #7
vilfort is offline vilfort  United States
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Hmm... there seems no reason why we could not grab two of the SCT20N120's and run them as a Circlotron. Make them source followers... Then, for the tube fans, we then run the voltage amplification section with tubes.

I am currently running a hybrid Circlotron with 4 X 2SK1058. Sounds good - but perhaps the SiC's could take this to the next level. Digikey sells the SCT20N120 at ~$20/SiC.

D.
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