Maybe it’s some mistake in the chart or it is observable only at chip temperature of 25°C.
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or is it just remaining of apple pie , which some Geek had for breakfast ..... while preparing graphs
dunno - I'll check mine in few days ....... need first to sort some other things
dunno - I'll check mine in few days ....... need first to sort some other things
My appologize.
With much more attention put now, here comes the results:
COLD Start UP - Left channel - V over R27 = 40 mV => Ig = 0,4mA
WARM - 15 min -Left channel - V over R27 = 0 mV => Ig = 0 mA
COLD Start UP - Left channel - V over R32 = 20 mV => Ig = 0,2mA
WARM - 15 min -Left channel - V over R32 = 0 mV => Ig = 0 mA
COLD Start UP - Right channel - V over R27 = 0 mV => Ig = 0 mA
WARM - 15 min -Right channel - V over R27 = 0 mV => Ig = 0 mA
COLD Start UP - Right channel - V over R32 = 0 mV => Ig = 0 mA
WARM - 15 min -Right channel - V over R32 = 0 mV => Ig = 0 mA
Seems taking rakija and measuring is not going hand by hand😎
Sorry again for doing first measurements without paying too much attention. Boards are not so easy accessible....
Wow, you have sharp eyes. My sensitivity is down to
100 nA, and I don't see that for Vgs from 0 to
the value for 3A Ids, and for Vds of 0 to 40V.
In any case, even 0.4 ma looks to be a lot.
😎
Thanks Mr. Pass for Your kind comments.
I must take another Zenovacha 😉 and I'm shure it will come down to Zero Ohma after that. Seriously speaking , most probably it is about bad contact connection during measurements. Soon I will replace 3W resistors with a MOX type, and will take out the boards and will re-check one more time. Seems to me that really there shoudn't be a problem if some uA of Ig ig flowing. Once more time, thank You very much for a Gorgeous Amplifier made with SS Mosfets. 😀
Well, then what do you think, what could be that bl**dy thing in the corner?
- It looks like 2-3mA @1.5V Vgs
- It rises at lower Vgs
- It isn’t dotted line meaning it’s measured at 25°C
As temperature rises the curve moves to the left and Ig becomes immeasurable, in most cases. Spavleski has apparently OK device but it shows some measurable Ig that disappears after warm up. Could it be an expected behavior with variations from device to device? Or simply the chart is misprinted?
- It looks like 2-3mA @1.5V Vgs
- It rises at lower Vgs
- It isn’t dotted line meaning it’s measured at 25°C
As temperature rises the curve moves to the left and Ig becomes immeasurable, in most cases. Spavleski has apparently OK device but it shows some measurable Ig that disappears after warm up. Could it be an expected behavior with variations from device to device? Or simply the chart is misprinted?
Sorry to bother, would you care (for the sake of science) to measure Vgs along with Igs next time? It seems Ig becomes measurable at cold start and with lower Vgs (is it too complicated to try it with lower bias current?).
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I have impression that Papa already said his results ........ and he certainly have more specimens to play with
I know for 12 pcs of SSouths in entire Serbia
even if you triple that .... it's funny
I know for 12 pcs of SSouths in entire Serbia
even if you triple that .... it's funny
I'll play a bit soon (in a week or two), during MOX replacement. Will post findings here. 😎
Any news ?
Yesterday I found the same problem in my new tube / Jfet project. Using a pair of the SJEP120R100A having highly different gate input currents :-( The driver is a 6SN7 @ 8 mA cathode follower. It seems to work after 30 minutes screwing at the pots and increased heatsink temperature....
Looks like this strong variation in the Jfets will needs extra attention...😱
Tubefan
Yesterday I found the same problem in my new tube / Jfet project. Using a pair of the SJEP120R100A having highly different gate input currents :-( The driver is a 6SN7 @ 8 mA cathode follower. It seems to work after 30 minutes screwing at the pots and increased heatsink temperature....
Looks like this strong variation in the Jfets will needs extra attention...😱
Tubefan
We were very lucky to be able to get hold of a sizable batch of SJEP120R100s.
Today we took 9 of them out at random, and curve traced them.
Vds was 25V, and case held at 25°C by a huge block of aluminium.
No time to heat up to 60°C today.
You can judge for yourself the chances of getting good match sets with a small matching pool.
At current asking prices, rejects will be horrendously expensive.
Patrick
Today we took 9 of them out at random, and curve traced them.
Vds was 25V, and case held at 25°C by a huge block of aluminium.
No time to heat up to 60°C today.
You can judge for yourself the chances of getting good match sets with a small matching pool.
At current asking prices, rejects will be horrendously expensive.
Patrick
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EUVL,
While Vgs defintely appears to be all over the place, have you had a chnce to check for consistency of Yfs? I have 8 that are pretty well matched, just have to check their yfs. Also, will you be checking for leakage?
While Vgs defintely appears to be all over the place, have you had a chnce to check for consistency of Yfs? I have 8 that are pretty well matched, just have to check their yfs. Also, will you be checking for leakage?
If you cannot find proper Vgs pairs, why would you bother with the other two parameters ?
Patrick
Patrick
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