Power JFETs in production

[Kosst Amojan]

I'm pretty much a nube here, so I'm not exactly sure what makes for a good audio power JFET, but I got bored last night and found that Mouser is stocking and selling UnitedSiC power JFETs in TO-247 packages. They're making these things rated up to 85 amp and 650V. I'm too green to read the data sheet and really understand it, but I wanted to toss it out there for the crowd and see what I can learn.

SiC JFETs | United Silicon Carbide Inc.

 

[Lingwendil]

P-channel? Hmmmm. Gate capacitance seems pretty high, so it would probably need a beefy driver stage. Expensive too.

 

[MOER]

Power Jfet

No such thing as a POWER JFET!
Jfets are small signal devices, MOSFETs are power devices.

 

[djmiddelkoop]

No such thing as a POWER JFET!

Look at the data sheets, it is a power FET, in fact, it looks like a VFET.

 

[vdi_nenna]

No such thing as a POWER JFET!
Jfets are small signal devices, MOSFETs are power devices.

That's not correct. SemiSouth made power Jfets and they are used in the First Watt J2. I used them in a First Watt F6.

SemiSouth in no longer in business, but there are other power jfets out there. Sometimes the descriptions are misleading, so it's best to ask someone who understands the specifications and manufacturing process for power jfets.

SemiSouth SiC Power JFETs

SiC JFETs target high-end audio | Elektor Magazine

 

[Elvee]

They are actually jFETs, not MOSFETs, and they are N-channel......

 

[vdi_nenna]

Reasonable price at mouser. Anyone want to build something?

UJ3N065080K3S UnitedSiC | Mouser

The gate capacitance on a IFRP240 is 1300 typical.
630pF on this jfet.

The IRFP240 and UJ3N065080K3S are a pin to pin match. Doesn't prove anything but...

 

[JMFahey]

Very reasonable price for such a beast.

Might order a pair and see what can I do with them.

 

[Soundhappy]

Anyone want to build something?

Always!
Thanks Vdi_nenna for the link of Your jfet interesting discovery

 

[vdi_nenna]

Always!
Thanks Vdi_nenna for the link of Your jfet interesting discovery

I didn't find it. Original poster found it, although this jfet has been talked about in other threads. I have a couple of these jfet spec sheets in my parts folder from 2017.

 

[Mr Evil]

Interesting, but is there any reason to prefer these over depletion MOSFETs? Small signal JFETs are useful for low noise, but that isn't important for the sort of use big devices like these would be put to. It would be a different matter if they were available in complementary pairs...

 

[Kosst Amojan]

So something like that could feasibly be used in an amplifier output stage?

 

[Zen Mod]

I believe Pa said something useful about some of SICs from regular production ... but I simply didn't remember where and when

 

[vdi_nenna]

Nelson Pass said that power jfets used in simple circuits provide less distortion than a mosfet in the same circuit.

PassDiy

 

[Kosst Amojan]

He talked about JFET topologies at BA 2016. I'd seen UnitedSiC was working towards these a few months ago, but this is the first I've seen of them on sale. If I recall he said he expected to see some eventually because they're more efficient than MOSFETs in switching power supplies like those used in solar installations and electric cars.

Like I said, I don't know a whole lot, but the ratings on those things look pretty impressive.

 

[Zen Mod]

yeah ..... but we are always looking what's transfer characteristic like in 20-30Vdc and ~2Adc region

practically - either U-I graph , or table as vdi_ posted

 

[yoaudio]

SiC Sissy amp.

 

[vdi_nenna]

It's all good and we can still build a lot of nice circuits with just a N-Ch JFET.
Just ask the tube guys.

I remember paying $88 for a matched pair of SemiSouth Jfets.
Be nice to have some around that are not as expensive.

 

[vdi_nenna]

practically - either U-I graph

So you are saying until someone runs tests on actual devices for a given voltage and current, we won't know if they are usable?

 

[bwaslo]

Well, there is a SPICE model for it ...
https://unitedsic.com/wp-content/uploads/spice/UJ3N065080K3S.txt