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Old 8th February 2013, 08:16 PM   #91
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I'm not so sure that the "don't need" part of 1200v devices is exactly correct. A bit depends on your point of view as to what you want to build. Obviously for most audio applications that much voltage is nutz. But if you think about substitution for vacuum tubes, the voltage capability starts to look like a benefit...

but an even smaller market segment... being commercial is difficult.

Can we do this in a small building, in the dead of night, with just a few people, relatively small quantities, using surplus fab gear... or leasing time in a real fab?
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Old 9th February 2013, 12:44 AM   #92
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Originally Posted by bear View Post
Can we do this in a small building, in the dead of night, with just a few people, relatively small quantities, using surplus fab gear... ?
You must have visited the fab we ran at the university (Edwards building) to get SemiSouth started. You've captured it nearly perfectly. (By the way, I'm not kidding...)
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Old 9th February 2013, 01:09 AM   #93
eyoung is offline eyoung  United States
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Originally Posted by buzzforb View Post
I think this is starting to get REAL interesting.
Yes it is.....

E in the nice warm south
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Old 9th February 2013, 12:01 PM   #94
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Originally Posted by bear View Post
I'm not so sure that the "don't need" part of 1200v devices is exactly correct. A bit depends on your point of view as to what you want to build. Obviously for most audio applications that much voltage is nutz. But if you think about substitution for vacuum tubes, the voltage capability starts to look like a benefit...

but an even smaller market segment... being commercial is difficult.

Can we do this in a small building, in the dead of night, with just a few people, relatively small quantities, using surplus fab gear... or leasing time in a real fab?
bear: The sonic value of Vds = 1200V remains to be determined. A question maybe: are the lower Vds values of 25-200 V protected by the attendant patents of Casady et al?
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Old 9th February 2013, 02:02 PM   #95
flg is offline flg  United States
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A Vds "value", spec or breakdown capability, Is not patentable. It is the physical structure and materials as they relate to the unique construction of the device. It is possible to have almost the same electrical parameters with a physically different structure without patent infringment.
It is very likely that these devices can replace tubes with very little circuit modification. I doubt we'll be able to replace a 300B with an R100 but, something more like a Pentode is likely?
Personally, If you look at the LU1014D device Vds vs. Ids graph, you can see the Red and Pink colored Vgs curves start looking triode like changing from the Blue, Brown and Violet looking Pentode like curves. What do the R100 and R085 curves look like in this area? The data sheet for them does not go that low in Ids (Vgs).
I have a few of each but, for the price I paid and the availability I'm not sure I want to try to do these measurements and have an accident. Although, I have the equipment at home and I'm snowed in, and under a driving ban, I still have power though, for now. Maybe after a few more Expresso and Bailey's.
I'll think about it.
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Old 9th February 2013, 02:19 PM   #96
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Thanks flg for the info above.
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Old 9th February 2013, 03:07 PM   #97
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A Vds "value", spec or breakdown capability, Is not patentable. It is the physical structure and materials as they relate to the unique construction of the device. It is possible to have almost the same electrical parameters with a physically different structure without patent infringment.
It is very likely that these devices can replace tubes with very little circuit modification. I doubt we'll be able to replace a 300B with an R100 but, something more like a Pentode is likely?
Personally, If you look at the LU1014D device Vds vs. Ids graph, you can see the Red and Pink colored Vgs curves start looking triode like changing from the Blue, Brown and Violet looking Pentode like curves. What do the R100 and R085 curves look like in this area? The data sheet for them does not go that low in Ids (Vgs).
I have a few of each but, for the price I paid and the availability I'm not sure I want to try to do these measurements and have an accident. Although, I have the equipment at home and I'm snowed in, and under a driving ban, I still have power though, for now. Maybe after a few more Expresso and Bailey's.
I'll think about it.
This may help
Attached Files
File Type: pdf R085.pdf (214.9 KB, 67 views)
File Type: pdf depletion jfet.pdf (63.6 KB, 58 views)
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Old 9th February 2013, 03:13 PM   #98
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Well, I put a little thought into it. I'm thinkin I can use the circuit attached below? Comments are welcome:
My Function Generator can produce a single + Pulse, I'm thinkin maybe 1ms long, so as not to get to much device heating. I will be going for the 25C data since anything else is a little difficult to do right now. Typically we do these measurements within 100-200uS. We'll see what the measurements look like? I can also vary the pulse amplitude in relatively small steps.
The 100 ohm should'nt induce much of any error but, save me from oscilating to death. One of those accidents I was thinkin of.
The .05 ohm Drain R is "current shunt" to measure the Ids. It's big enough to measure voltage accurately but, not big enough to eat up my Drain voltage when current is flowing. It's also big enough physically to not induce to much Tc variation from heating.
I will use a storage scope triggered on the Func Gen pulse to capture these 2 voltages. In the past I remember having to use some diodes in the set-up to avoid the scope input saturation due to the range it needs to be on but, I don't think that's an issue here. That's probably the Rdson test I'm thinkin of.
Does anyone see any issues? Have any suggestions?
Attached Images
File Type: gif Vds vs Ids test.GIF (3.0 KB, 202 views)
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Last edited by flg; 9th February 2013 at 03:18 PM.
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Old 9th February 2013, 03:23 PM   #99
Gyuri is offline Gyuri  Hungary
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This is almost exactly, what about I'm thinking.
But I'm don't want to kill my last mohicans.
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Old 9th February 2013, 03:26 PM   #100
Gyuri is offline Gyuri  Hungary
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My Toellner 7711 function generator has a DC offset function it's perhaps an useful feature in this case, isn't it?
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