Hello Stefano
I will have to wait for Grey to get back to me about pricing and payment then wait for potential delivery. please bear with me till Ighave at least received the chips.
regards
dave
I will have to wait for Grey to get back to me about pricing and payment then wait for potential delivery. please bear with me till Ighave at least received the chips.
regards
dave
Q2 MosFet
Hello all,
I'm glad the ordering is moving so smoothly (so far). I have tried to go through all the previous posts, until page 15, then I burned out.
I also read Mr. Pass's article on the Zen 8. I could not find recommendations for Q2, the power MosFet. Any suggestions would be appreciated. 🙂
Bruce
Hello all,
I'm glad the ordering is moving so smoothly (so far). I have tried to go through all the previous posts, until page 15, then I burned out.
I also read Mr. Pass's article on the Zen 8. I could not find recommendations for Q2, the power MosFet. Any suggestions would be appreciated. 🙂 Bruce
At this time, all Canadian buyers should have return e-mail from me. If any Canadians have not heard back from me, prompt me with an e-mail or post here.
Bruce,
Assuming a TO-247 case, I'd say that the IRFP044 would be running pretty close to the limit, voltage-wise. The IRFP140 and IRFP240 would be much better choices. Think in terms of 100V devices. Any of the most likely candidates will be able to handle the current (about 1A) and wattage (Pd roughly 25W). IRF has a number of TO-247 parts at 100V and above...take your pick.
Grey
Bruce,
Assuming a TO-247 case, I'd say that the IRFP044 would be running pretty close to the limit, voltage-wise. The IRFP140 and IRFP240 would be much better choices. Think in terms of 100V devices. Any of the most likely candidates will be able to handle the current (about 1A) and wattage (Pd roughly 25W). IRF has a number of TO-247 parts at 100V and above...take your pick.
Grey
Bruce,
IRF(insert P here, P seems to indicate the TO-247 case style)140
See if that clears up some of the mystery.
Overkill? Hey, we're DIY. Overkill is our middle name.
Bear in mind that it's a good idea to derate most specs by at least a factor of 2 for class A audio use. Also remember that using a 50V rail (for instance) will typically leave you with 25V across the device at idle. So far, so good. The thing is that, at full power, you'll be running that device to the rail, hence roughly doubling the voltage that the device sees. Kinda puts a different perspective on things. Suddenly the 60V rating (quoting from memory) of the IRFP044 doesn't look so generous.
Grey
IRF(insert P here, P seems to indicate the TO-247 case style)140
See if that clears up some of the mystery.
Overkill? Hey, we're DIY. Overkill is our middle name.
Bear in mind that it's a good idea to derate most specs by at least a factor of 2 for class A audio use. Also remember that using a 50V rail (for instance) will typically leave you with 25V across the device at idle. So far, so good. The thing is that, at full power, you'll be running that device to the rail, hence roughly doubling the voltage that the device sees. Kinda puts a different perspective on things. Suddenly the 60V rating (quoting from memory) of the IRFP044 doesn't look so generous.
Grey
Folks, as a matter of both statistics and logistics, I need you to think in terms of smaller groupings for matched devices; perhaps 8, 10, or 12. I have people requesting very, very large single groups and it's approaching the point where I will have to strip the entire population of parts of certain values in order to make up the matched lots. Obviously, that's not fair to the members who want to match their own--they'll end up with holes in their values.
My intention is to try to hit 10mV windows, i.e. +-5mV. There may be one or two millivolts drift to either side, but that's my goal. If you approach it from a background in statistics--or if you refer to Nelson's Vgs curve posted elsewhere and work it through that way--you'll soon see that if someone asks for, say, 100 matched parts, it's going to require going through a huge number of individual units to meet that request. Huge meaning thousands in some cases.
Incidentally, I'm getting a slightly different distribution from the one Nelson posted. On his graph, there's a shorter bar to the left of the peak of the bell curve. Mine is just to the right, just doing an eyeball survey of the quantities I've graded so far.
Also note that these parts are not behaving the way tubes of IRF MOSFETs do. There's not a more-or-less smooth gradient going from one end of the tube to the other. I'll have a high value, then a low one, then perhaps as many as three or four that cluster towards the center, then back to another low one. Scattershot. I had one tube that had a notable preponderance of lower values, followed later on by another tube that leaned heavily towards higher ones. One tube clustered more towards the middle. The rest have been all over the map.
The devices do not have stamper numbers that might hint where they originated in the original wafer. I do not know what their manufacturing process is, nor do I know how they move their parts from manufacturing to packing. Presumably it involves a fair amount of jumbling around, judging from the value trends I'm seeing. Or lack of same.
Anyway, please think in terms of smaller sets. It'll make life easier for your fellow DIYer.
(Not to mention me...)
Grey
My intention is to try to hit 10mV windows, i.e. +-5mV. There may be one or two millivolts drift to either side, but that's my goal. If you approach it from a background in statistics--or if you refer to Nelson's Vgs curve posted elsewhere and work it through that way--you'll soon see that if someone asks for, say, 100 matched parts, it's going to require going through a huge number of individual units to meet that request. Huge meaning thousands in some cases.
Incidentally, I'm getting a slightly different distribution from the one Nelson posted. On his graph, there's a shorter bar to the left of the peak of the bell curve. Mine is just to the right, just doing an eyeball survey of the quantities I've graded so far.
Also note that these parts are not behaving the way tubes of IRF MOSFETs do. There's not a more-or-less smooth gradient going from one end of the tube to the other. I'll have a high value, then a low one, then perhaps as many as three or four that cluster towards the center, then back to another low one. Scattershot. I had one tube that had a notable preponderance of lower values, followed later on by another tube that leaned heavily towards higher ones. One tube clustered more towards the middle. The rest have been all over the map.
The devices do not have stamper numbers that might hint where they originated in the original wafer. I do not know what their manufacturing process is, nor do I know how they move their parts from manufacturing to packing. Presumably it involves a fair amount of jumbling around, judging from the value trends I'm seeing. Or lack of same.
Anyway, please think in terms of smaller sets. It'll make life easier for your fellow DIYer.
(Not to mention me...)
Grey
My previous post is not meant to discourage you from ordering matched devices. Just plan on something like two sets of 10 or four sets of 12.
Yes, I know it's difficult to guess what you'll need when Nelson's Zen #8 only needs 1 per channel and I haven't posted my somewhat larger design yet. As guidance, think of an Aleph, where the active devices on top need to be matched as one group and the ones on the bottom need to be matched as a group...but they do not need to be matched together.
Grey
Yes, I know it's difficult to guess what you'll need when Nelson's Zen #8 only needs 1 per channel and I haven't posted my somewhat larger design yet. As guidance, think of an Aleph, where the active devices on top need to be matched as one group and the ones on the bottom need to be matched as a group...but they do not need to be matched together.
Grey
Grey, you are welcome to split my order up in smaller sets. Say, something like 10 matching devices in each set. No problem at all.
I just imagined the thrill it would be to have a large bag of matching devices; just grab in the bag, and they match😀 Wouldnt that be cool🙂
Steen
I just imagined the thrill it would be to have a large bag of matching devices; just grab in the bag, and they match😀 Wouldnt that be cool🙂
Steen
Thank you, Grey, for pointing it out it would not be fair to the people who are buying non-selected VFETs, to get the ones who come out of the selectin process...
Being one of the unfortunate individuals, who does not live either in USA, Canada or Mexico, therefore not being able to buy selected parts from you - which I would if I could!, (any for that matter, having to wait longer and paying more than those who would get them from you), we in Europe would really appreciate if you could sell unselected devices (not those who would go first through a selection process), to DHOLE, who would then sell them to us inside Europe.
Andrej
Being one of the unfortunate individuals, who does not live either in USA, Canada or Mexico, therefore not being able to buy selected parts from you - which I would if I could!, (any for that matter, having to wait longer and paying more than those who would get them from you), we in Europe would really appreciate if you could sell unselected devices (not those who would go first through a selection process), to DHOLE, who would then sell them to us inside Europe.
Andrej
Steen,
Good for you that you can get these devices directly from Grey - the rest of us in Europe not being so lucky!
Thanks to Dave (dhole), we shall eventually still be able to get them, but we shall have to rely on the quantity we get from him to get out of it selected devices, so clearly we would be at quite a disadvantage if he would receive the remains out of a selected lot process (just as Grey has pointe it out).
Andrej
Good for you that you can get these devices directly from Grey - the rest of us in Europe not being so lucky!
Thanks to Dave (dhole), we shall eventually still be able to get them, but we shall have to rely on the quantity we get from him to get out of it selected devices, so clearly we would be at quite a disadvantage if he would receive the remains out of a selected lot process (just as Grey has pointe it out).
Andrej
I'm doing what I can to try to keep this as fair as possible for everybody.
Dave, as I understand it, is still mulling things over. If things don't work out, then we'll see what else can be arranged. One way or another, we'll get people taken care of.
I still find Australia to be rather under-represented. They must be in the middle of a holiday over there, as I can't imagine that such a mighty nation of DIYers has suddenly lost its can-do attitude. Drink one for me, fellas.
Grey
Dave, as I understand it, is still mulling things over. If things don't work out, then we'll see what else can be arranged. One way or another, we'll get people taken care of.
I still find Australia to be rather under-represented. They must be in the middle of a holiday over there, as I can't imagine that such a mighty nation of DIYers has suddenly lost its can-do attitude. Drink one for me, fellas.
Grey
I am sure Grey will make a fair deal with Dhole! I feel quite sure he will send untouched tubes of J-fets to Dhole😎 If necessary, I can cut deeper, regarding the amount of matched fets!! I hope nobody will ever claime me responsiple for getting bad matching fets! Grey is nobody's fool, (sorry for the language!) and he would never put his reputation on line for that. Correct me if I am wrong. I do understand though the thoughts of yours, creeping in. I think you can rest assured 🙂 Dont worry at all, if Grey has trouble matching the devices, I will be the first in line to relieve him!!
Steen
- Status
- Not open for further replies.