bcarso
Well-known member
It appears that Linear Integrated Systems have a replacement part finally available for the discontinued Toshiba 2SK389, namely the LSK389. The specs look very good.
JFET News
- Thread starter bcarso
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Samuel Groner
Well-known member
Thanks for the notification! Time to get a few samples.
Samuel
Samuel
Svart
Well-known member
oh it's about time! my secret source was getting low.. :green:
BradAvenson
Well-known member
I wonder why they didn't layout the dual so that you could stuff two singles in its place. Maybe that would be too convenient.
http://www.linearsystems.com/
http://www.linearsystems.com/datasheets/LSK389.pdf
LSK170 family SPICE model
Also of interest:
dual JFET voltage controlled resistor, high pinchoff voltage ~10V, modest on-resistance ~150Ω. Said to be like Siliconix (InterFET) VCR11N.
InterFET has a good (though big) FET databook on line.
http://www.linearsystems.com/datasheets/LSK389.pdf
LSK170 family SPICE model
Also of interest:
dual JFET voltage controlled resistor, high pinchoff voltage ~10V, modest on-resistance ~150Ω. Said to be like Siliconix (InterFET) VCR11N.
InterFET has a good (though big) FET databook on line.
bcarso
Well-known member
[quote author="BradAvenson"]I wonder why they didn't layout the dual so that you could stuff two singles in its place. Maybe that would be too convenient.[/quote]
This is an odd outfit, but I'm glad they are able to exist. They also just got rights to make the teeny fast DMOS parts like the SD210, which are useful for certain switching apps.
When I corresponded with them the man told me that the SK389 would not have a substrate connection. Now I see that there are two of them (!) on the surface-mount package, although there is no indication about any connection to the metal case of the leaded part. I mention this because having access to this connection allows one to bootstrap out the gate-substrate capacitance for super-low-input C requirements.
Meanwhile Toshiba still makes all of one dual N chip but only in surface mount packages and with the sources tied together and no substrate connection brought out
If I had unlimited funds I'd contract with LIS to do custom parts, since they clearly know what they are doing. They might indeed be persuaded to do some P-channels but that is not in their plans at the moment, iirc. The SK389 is not a slavish duplicate of the Toshiba device but is an interdigitated part, which their guy said would result in still lower noise. It also should make for better matching of each FET.
This is an odd outfit, but I'm glad they are able to exist. They also just got rights to make the teeny fast DMOS parts like the SD210, which are useful for certain switching apps.
When I corresponded with them the man told me that the SK389 would not have a substrate connection. Now I see that there are two of them (!) on the surface-mount package, although there is no indication about any connection to the metal case of the leaded part. I mention this because having access to this connection allows one to bootstrap out the gate-substrate capacitance for super-low-input C requirements.
Meanwhile Toshiba still makes all of one dual N chip but only in surface mount packages and with the sources tied together and no substrate connection brought out
If I had unlimited funds I'd contract with LIS to do custom parts, since they clearly know what they are doing. They might indeed be persuaded to do some P-channels but that is not in their plans at the moment, iirc. The SK389 is not a slavish duplicate of the Toshiba device but is an interdigitated part, which their guy said would result in still lower noise. It also should make for better matching of each FET.
Samuel Groner
Well-known member
They didn't improve on the 20 mV max offset though... :sad:
Samuel
bcarso
Well-known member
[quote author="Samuel Groner"]
Samuel[/quote]
Probably a CYA number though.
They didn't improve on the 20 mV max offset though... :sad:
Samuel[/quote]
Probably a CYA number though.
FredForssell
Well-known member
Yeah, the samples that I have here are a 6-lead metal can (to-72?), and an 8 pin smt/SO-8 type package. I haven't test either yet. I guess I'm still waiting to see if the do the P-channel devices.
Cheers,
Svart
Well-known member
What?? damn I just went to look at the datasheets and saw the footprints before you guys posted about them.. I have boards that are layed out for the 6pin SIP that the original sk389 was.. guess i'm going to have to use discrete sk170s.
guess i'm going to have to use discrete sk170s.bcarso
Well-known member
[quote author="Svart"]What?? damn I just went to look at the datasheets and saw the footprints before you guys posted about them.. I have boards that are layed out for the 6pin SIP that the original sk389 was.. guess i'm going to have to use discrete sk170s.[/quote]
You mean 7 pin I guess? Or were you just going to clip the central substrate lead off?
Anyway, I can give you some 389V's if you don't need a bunch and if that Idss bracketing is o.k.
guess i'm going to have to use discrete sk170s.[/quote]You mean 7 pin I guess? Or were you just going to clip the central substrate lead off?
Anyway, I can give you some 389V's if you don't need a bunch and if that Idss bracketing is o.k.
Svart
Well-known member
you know now that you mention it I dug through my boxes of bits n' pieces and they do have 7 pins.. it's been so long since I had a chance to work with them I had forgotten all about the substrate lead... I just remember laying the boards out for either two discrete sk170s side by side or one sk389 , substrate not utilized on this design.
V's will work fine, just a few electret capsule amps, been toying with ideas too.. when I get them where I am happy i'll be dropping them on the group.
check this out: some spice models for the sk389 and sk170.
http://www.diyaudio.com/forums/showthread/t-1977.html
also dug up something interesting using the sk389:
http://www.borbelyaudio.com/pics/EB-602-210%20final.pdf
that last one has given me a few ideas if you catch my drift.. :green:
How is that preamp stage coming? I still have some ideas for it..
:guinness:
I just remember laying the boards out for either two discrete sk170s side by side or one sk389 , substrate not utilized on this design. V's will work fine, just a few electret capsule amps, been toying with ideas too.. when I get them where I am happy i'll be dropping them on the group.
check this out: some spice models for the sk389 and sk170.
http://www.diyaudio.com/forums/showthread/t-1977.html
also dug up something interesting using the sk389:
http://www.borbelyaudio.com/pics/EB-602-210%20final.pdf
that last one has given me a few ideas if you catch my drift.. :green:
How is that preamp stage coming? I still have some ideas for it..
:guinness:
Samuel Groner
Well-known member
Note that Linear System has SPICE models on their page--somehow I trust these more than what is floating around on the net.
Samuel
Svart
Well-known member
duly noted. :thumb:
however the spice models on linear's website are for their parts and there seems to be a small amount of difference between their parts and the originals no?
however the spice models on linear's website are for their parts and there seems to be a small amount of difference between their parts and the originals no?
Samuel Groner
Well-known member
Probably--I tried most (I think all?) of the SPICE models you linked and there were IIRC big differences between them, so I opted for the Linear ones in the hope of good coherence.
Anyway, the big variations in Idss and Vgs etc. between different samples are never truely modelled so you need a good deal of knowledge when working with JFETs--I'm working on it...
Samuel
Anyway, the big variations in Idss and Vgs etc. between different samples are never truely modelled so you need a good deal of knowledge when working with JFETs--I'm working on it...
Samuel
bcarso
Well-known member
Thanks for that DIY material. I will have to see which of the 170 models is closest to the one I got from Orcad and ported into Circuitmaker.
Of course only if the particular part has the same Idss and Vp as the model will the particular model work that well, so to really get to it I suppose you should know all the assumptions and enter data for a given sample.
Now that would be a great little industry: screen FETs with a really good curve tracer and ship the parts with a model for each part!
(EDIT for spelling and grammar)
Of course only if the particular part has the same Idss and Vp as the model will the particular model work that well, so to really get to it I suppose you should know all the assumptions and enter data for a given sample.
Now that would be a great little industry: screen FETs with a really good curve tracer and ship the parts with a model for each part!
(EDIT for spelling and grammar)
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