Well, not really shipping now, as I still have some matching to do.
R100 should be shipping out by end of next week.
R550 will take 2 weeks longer.
All Semisouth JFET will be sold Vgs matched.
The stock for R100 is limited, and I have many pre-order to fulfill, so first come first serve.
Stock for R550 is plenty, so no problem.
---------------------------
SJEP170R550 - new 1700V part with lower capacitance, lower transconductance, lower power dissipation.
Price: $20/ea for the first 4 pcs, $17/ea for the 5th to 8th pcs, $16/ea from the 9th pcs onward
SJEP120R100 - the original part used in FirstWatt J2.
Price: $29/ea for the first 4 pcs, $26/ea for the 5th to 8th pcs, $25/ea from the 9th pcs onward
Qty____R550_____R100
_1______$20______$29
_2______$40______$58
_4______$80_____$116
_8_____$148_____$220
12_____$212_____$320
16_____$276_____$420
The above list is just calculated for your convenience, you can purchase in any quantity.
The quantity discount will also be valid if you buy a combination of R100 and R500, i.e. $3/ea off base price for 5th to 8th pcs and $4/ea off base price for 9th pcs onward.
Free shipping for orders >=$50, paypal fee inclusive.
$1 will be donate to the forum for every 2pcs of SS JFET sold.
For the list of other parts that I'm selling, as well as more details about how to order, please view my other post.
R100 should be shipping out by end of next week.
R550 will take 2 weeks longer.
All Semisouth JFET will be sold Vgs matched.
The stock for R100 is limited, and I have many pre-order to fulfill, so first come first serve.
Stock for R550 is plenty, so no problem.
---------------------------
SJEP170R550 - new 1700V part with lower capacitance, lower transconductance, lower power dissipation.
Price: $20/ea for the first 4 pcs, $17/ea for the 5th to 8th pcs, $16/ea from the 9th pcs onward
SJEP120R100 - the original part used in FirstWatt J2.
Price: $29/ea for the first 4 pcs, $26/ea for the 5th to 8th pcs, $25/ea from the 9th pcs onward
Qty____R550_____R100
_1______$20______$29
_2______$40______$58
_4______$80_____$116
_8_____$148_____$220
12_____$212_____$320
16_____$276_____$420
The above list is just calculated for your convenience, you can purchase in any quantity.
The quantity discount will also be valid if you buy a combination of R100 and R500, i.e. $3/ea off base price for 5th to 8th pcs and $4/ea off base price for 9th pcs onward.
Free shipping for orders >=$50, paypal fee inclusive.
$1 will be donate to the forum for every 2pcs of SS JFET sold.
For the list of other parts that I'm selling, as well as more details about how to order, please view my other post.
Attachments
Matching of TO-247 Semisouth JFET
20 pcs at a time, CCS through all of them (from HP PS below the desk).
Id = 1.2165, ambient 27degC
The precision and short term stability of Vgs reading is quite good, when stabilized it usually fluctuation within a range of +/-0.05mV (really takes 6.5 digit meter to see it). A small swing of hand will increase Vgs by about 1mV (reaction time about 2-3 second), and then you will see it slow drop back.
Repeatability and long term stability needs to be improved. typically I see about 3mV of difference when I retest at different position or time, in worst case I have seen 7+mV changes. I believe this is due to air-movement and the variation in the resistance of the socket (each socket to pin connection cause about 7-10mV drop at 1.2A). If I test at smaller Id, I expect the socket problem to be reduced.
Conclusion:
The first 2 decimals (0.x V and 0.0x V) are pretty reliable, the 3rd decimal place is useful but less accurate, the 4th decimal, although recorded on the JFETs I sent you, can be neglected.
For current sharing purpose, I think this accuracy is sufficient.
For matching of Gm to decrease of THD (if applicable to your design), this is also good enough as Vgs is not a indicator of Gm anyway.
I will try to improve it when I match R550 10 days later.
20 pcs at a time, CCS through all of them (from HP PS below the desk).
Id = 1.2165, ambient 27degC
The precision and short term stability of Vgs reading is quite good, when stabilized it usually fluctuation within a range of +/-0.05mV (really takes 6.5 digit meter to see it). A small swing of hand will increase Vgs by about 1mV (reaction time about 2-3 second), and then you will see it slow drop back.
Repeatability and long term stability needs to be improved. typically I see about 3mV of difference when I retest at different position or time, in worst case I have seen 7+mV changes. I believe this is due to air-movement and the variation in the resistance of the socket (each socket to pin connection cause about 7-10mV drop at 1.2A). If I test at smaller Id, I expect the socket problem to be reduced.
Conclusion:
The first 2 decimals (0.x V and 0.0x V) are pretty reliable, the 3rd decimal place is useful but less accurate, the 4th decimal, although recorded on the JFETs I sent you, can be neglected.
For current sharing purpose, I think this accuracy is sufficient.
For matching of Gm to decrease of THD (if applicable to your design), this is also good enough as Vgs is not a indicator of Gm anyway.
I will try to improve it when I match R550 10 days later.
Attachments
Dear Patrick,
I am not sure if bolting them all onto a big aluminum block will get more accurate result.
When there is a common aluminum block, the temperature Tj of each FET is not only determined by its own heat dissipation (which is directly proportional to its Vgs with single CSS). Instead, the Tj is mostly determined by the temperature of the aluminum block, which is determined by the heat dissipation of all the FETs on the block, which is ultimately determined by the average Vgs of all the FETs.
The problem is, for each group of 20 FETs, their average Vgs can be quite different. The same piece of FET, when measured with another 19 FETs of average Vgs=1.0V, verses with a different group of 19 FET with average Vgs=1.2V, will give you very different result, becase the delta between the aluminum and ambient temperature differs by about 20%.
I did my test in this way, so that all heat is dissipated by natural convection + radiation of the TO-247 package, which is highly uniform, and the temperature of each FET is only minimally disturbed by the neighbouring FET (unlike in the all bolt together case, the Tj is mostly DECIDED by the Vgs of other FETs)
In my hand swing test, it has shown that the mass of the TO-247 device has reasonably sufficient thermal mass to reject fluctuation
One obvious limitation I see in my method is that it limits the maximum power that each FET can handle. With RthJA of about 50degC/W, up to 2W is possible, but I will keep more safety margin unless it is SiC (semisouth) or has larger than TO-247 package (2SK1530/J201).
Regard,
Zhou Fang
I am not sure if bolting them all onto a big aluminum block will get more accurate result.
When there is a common aluminum block, the temperature Tj of each FET is not only determined by its own heat dissipation (which is directly proportional to its Vgs with single CSS). Instead, the Tj is mostly determined by the temperature of the aluminum block, which is determined by the heat dissipation of all the FETs on the block, which is ultimately determined by the average Vgs of all the FETs.
The problem is, for each group of 20 FETs, their average Vgs can be quite different. The same piece of FET, when measured with another 19 FETs of average Vgs=1.0V, verses with a different group of 19 FET with average Vgs=1.2V, will give you very different result, becase the delta between the aluminum and ambient temperature differs by about 20%.
I did my test in this way, so that all heat is dissipated by natural convection + radiation of the TO-247 package, which is highly uniform, and the temperature of each FET is only minimally disturbed by the neighbouring FET (unlike in the all bolt together case, the Tj is mostly DECIDED by the Vgs of other FETs)
In my hand swing test, it has shown that the mass of the TO-247 device has reasonably sufficient thermal mass to reject fluctuation
One obvious limitation I see in my method is that it limits the maximum power that each FET can handle. With RthJA of about 50degC/W, up to 2W is possible, but I will keep more safety margin unless it is SiC (semisouth) or has larger than TO-247 package (2SK1530/J201).
Regard,
Zhou Fang
By large aluminium block, I meant something like 200x300x80mm. You can easily calculate how much mass there is and how much energy you need to heat this up by 0.1°C. On top of that you can easily monitor the aluminium block temperature with a thermal couple from some multimeters.
You are speaking from theory, I speak from years of experience.
BR,
Patrick
You are speaking from theory, I speak from years of experience.
BR,
Patrick
R550 are matched, all R550 orders will be ship out later today (19th Apr Mon), very sorry for the long wait.
R550 are match in a similiar way as the R100 except:
- They are tested with Id = 0.5043A, instead of 1.2+A for R100. This should be closer to the Id that most will be using the R550 at, since it has higher RthJC.
- Vgs is read out by directly probing the legs of the JFET, instead of from the pink extension wire. This remove the inconsistant voltage drop due to resistance of the pin(leg) socket connection.
The repetability of this R550 testing setup is generally below 1mV, with very few exceptions that goes slighly above 1mV.
R550 are match in a similiar way as the R100 except:
- They are tested with Id = 0.5043A, instead of 1.2+A for R100. This should be closer to the Id that most will be using the R550 at, since it has higher RthJC.
- Vgs is read out by directly probing the legs of the JFET, instead of from the pink extension wire. This remove the inconsistant voltage drop due to resistance of the pin(leg) socket connection.
The repetability of this R550 testing setup is generally below 1mV, with very few exceptions that goes slighly above 1mV.
Kerafol Keratherm Red 86/83 Isolators TO-247 will be available from 1st May.
$1 each when you buy with SS SiC JFET.
It is the same part as is the last http://www.diyaudio.com/forums/group-buys/144076-gb-kerafol-keratherm-red-isolators-220-247-a.html
$1 each when you buy with SS SiC JFET.
It is the same part as is the last http://www.diyaudio.com/forums/group-buys/144076-gb-kerafol-keratherm-red-isolators-220-247-a.html
I believe you can swap the IRF610 in D1 I/V with R550 with minimal changes, just as NP said that R100/R125 is almost a drop-in replacement for IRFP240.
But paralleled 2SK170 can also be used in I/V with sufficient transconductance.
As to which one is better, I can't comment on it as I'm either good at EE nor have I tried them out.
Other Usage for R550 can be building head-amp for high impedance headphones like the 300ohm Sennheisers.
For all SS JFETs there's already threads discussing about them in the PASSLAB forum, you can read through them if you have not yet done it.
But paralleled 2SK170 can also be used in I/V with sufficient transconductance.
As to which one is better, I can't comment on it as I'm either good at EE nor have I tried them out.
Other Usage for R550 can be building head-amp for high impedance headphones like the 300ohm Sennheisers.
For all SS JFETs there's already threads discussing about them in the PASSLAB forum, you can read through them if you have not yet done it.
yeah I only asked here in case you had some specific knowledge albeit second hand or first hand. thats the idea behind getting both though, so I can see which works best to my ears too. i'm already sorted for headamps, but will keep it in mind. I worry a little about the toshiba parts in this format for the D1 with no heatsink, guess I could jerry-rig one. anyway. yeah i'm keen; i'll grab some of both. will confirm numbers in the next day or so and send payment. I assume you wont be running out before then? getting any closer to the 085 matching being done?
will confirm asap, probably tomorrow
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