Hello,
I do not suppose that the J113 is any one’s darling so we will use that one for illustration. The J113 Datasheet tells us that the Idss is measured at 15VDC. I am using a Keysight SMU to supply a constant 15VDC and measure current. The SMU is freshly calibrated by Keysight.
See the attached photo of the test jig breadboard, schematic and test results.
To sooth those that will comment about temperature and such, I used tweezers and let the JFET plus resistors settle in the 64 degrees breeze coming through the window. The test voltage was applied with a quick pulse not to allow warming. I think of this as temperature controlled (cold) testing. (cold := no warming). I measured a handful, 50 or so J113’s, they fell into a bi-modal distribution as I placed them into like piles on the test bench. I saw Jackinnj mention this in another thread.
Results for the single J113 in the photo.
0 ohm resistor Idss = 10.7530mA
2.7 ohm resistor Id = 10.31280mA
10.0 ohm resistor Id = 9.2940mA
29.4 ohm resistor Id = 8.30586mA
100 ohm resistor Id = 4.56568mA
1000 ohm resistor Id = 0.848837mA
The resistors are RND55 Vishay metal film out of my parts bins.
To me it is looking like the JFETS can be matches sort of close to a target IDSS and the Id can be Custom adjusted with a carefully selected small source resistor.
I know that this stuff has been discussed on these pages before. I liked seeing it on my computer monitor so I shared it with DIYaudio.
Thanks DT
I do not suppose that the J113 is any one’s darling so we will use that one for illustration. The J113 Datasheet tells us that the Idss is measured at 15VDC. I am using a Keysight SMU to supply a constant 15VDC and measure current. The SMU is freshly calibrated by Keysight.
See the attached photo of the test jig breadboard, schematic and test results.
To sooth those that will comment about temperature and such, I used tweezers and let the JFET plus resistors settle in the 64 degrees breeze coming through the window. The test voltage was applied with a quick pulse not to allow warming. I think of this as temperature controlled (cold) testing. (cold := no warming). I measured a handful, 50 or so J113’s, they fell into a bi-modal distribution as I placed them into like piles on the test bench. I saw Jackinnj mention this in another thread.
Results for the single J113 in the photo.
0 ohm resistor Idss = 10.7530mA
2.7 ohm resistor Id = 10.31280mA
10.0 ohm resistor Id = 9.2940mA
29.4 ohm resistor Id = 8.30586mA
100 ohm resistor Id = 4.56568mA
1000 ohm resistor Id = 0.848837mA
The resistors are RND55 Vishay metal film out of my parts bins.
To me it is looking like the JFETS can be matches sort of close to a target IDSS and the Id can be Custom adjusted with a carefully selected small source resistor.
I know that this stuff has been discussed on these pages before. I liked seeing it on my computer monitor so I shared it with DIYaudio.
Thanks DT
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That's a little expensive for my pocket but if you like handy little instruments that plug into your PC, you could also use a Peak Atlas DCA 75 which comes with software and cable to draw nice curves on your PC screen. It's not bad as a curve tracer and makes great side-by-side graphic comparisons of several (IIRC, 12) small signal transistors at a glance.
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