JFETs from Linear Systems

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Exciting news! The diyAudio store is now the exclusive distributor for limited quantities of LSK170 and LSJ74 JFETs from Linear Systems.

Watch the announcement from Linear Systems on YouTube!

Please post any questions you have in this thread. We'll be posting information shortly about the difference between the grades. Depending on your application, different grades may be the most suitable.

A comment from Nelson on grades:

Nelson Pass said:
The B through D and most of the A would not be a problem for the ACA, and a slight adjustment would allow down to the 2.5 mA figure without problems. Most of my projects would want a B or C grade as most desirable, but it’s not a big deal.
 
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Hi Jason I was curious if we bought jfets from Linear Systems, would each one be individually marked by its idss such as 7mA?

It won't be marked.

LIS marks the parts prior to final test with just the part family number. LIS does not mark the grade on the part. Toshiba in the past marked the part with a colored dot:

LSK170A=GR (green)
LSK170B=BL (blue?)
LSK170C=V (violet)
LSK170D=toshiba never offered this grade of idss
LSK170E=toshiba never offered this grade of idss

LSJ74A=GR (green)
LSJ74B=BL (blue?)
LSJ74C=V (violet)
LSJ74D=toshiba never offered this grade of idss
LSJ74E=toshiba never offered this grade of idss
 
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Hi Jason I was curious if we bought jfets from Linear Systems, would each one be individually marked by its idss such as 7mA?

I had samples in the past from Linear System (LSK170 and dual jfets LSK389)
They are marked A B or C concerning Idss, corresponding to GR BL and V in the former K170 K389 from Toshiba
 
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Great to hear, but damn those lsj74's were expensive. Especially if you need a few of them matched...

We might offer matched pairs and quads in the future. To be confirmed.

Does anyone know what the odds are of finding a couple matched pairs of LSJ74's if one buys the minimum of 8?

Looks like Grade D is all that's available at the moment. Were the other grades available and just sold out?

Everything sold out very quickly. Currently the best way to find out about new stock is to subscribe to The diyAudio Store stock news and updates thread.

We already have new stock and are packaging it for sale - should be shipping in a week or two.
 
I recently purchased 8 each of LSK170C and LSJ74C from the store and performed measurements of IDSS and Gm at the IDSS current. I share the test results here.

LSK170C
IDSS Gm@Idss
mA mS
_____________
11.60 32.7
11.60 32.8
11.60 32.9
11.62 33.0
11.64 32.9
11.68 32.7
11.68 33.0
11.70 32.9

LSJ74C
IDSS Gm@Idss
mA mS
_____________
11.50 30.5
11.50 28.3
12.40 32.8
14.84 33.9
15.06 33.0
15.76 30.7
17.10 33.1

You can see that the LSK170 parts are nearly identical whereas the LSJ74 parts show a rather large spread of IDSS values. This is probably a reflection of the fab process for the J74 parts still being relatively new. Perhaps there are other factors involved of which I am unaware.
 
I recently purchased 8 each of LSK170C and LSJ74C from the store and performed measurements of IDSS and Gm at the IDSS current. I share the test results here.

LSK170C
IDSS Gm@Idss
mA mS
_____________
11.60 32.7
11.60 32.8
11.60 32.9
11.62 33.0
11.64 32.9
11.68 32.7
11.68 33.0
11.70 32.9

LSJ74C
IDSS Gm@Idss
mA mS
_____________
11.50 30.5
11.50 28.3
12.40 32.8
14.84 33.9
15.06 33.0
15.76 30.7
17.10 33.1

You can see that the LSK170 parts are nearly identical whereas the LSJ74 parts show a rather large spread of IDSS values. This is probably a reflection of the fab process for the J74 parts still being relatively new. Perhaps there are other factors involved of which I am unaware.

For comparison only, what VDS did you use to measure ?
Toshiba 2SK170 Datasheet shows Gm > 40mS for VDS=10V.
 
;)

ok!

So, this device has less Gm than k170 at equal conditions. But has no problem.

i wonder if it has a square law on "id vs vgs". i don't think so.
I measured Id and Gm with three different resistors (0R, 7.5R and 20R) from source to ground, with ground as the DC potential of the gate, and a 20mV, 1kHz sine wave on the gate. I suppose you might be able to infer something about the Id vs Vgs from my data.
 
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