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Old 25th March 2010, 10:47 PM   #41
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I am mostly interested in the transfer curves - the
relationship of Ids, Vgs and Vds. The current crop of FET
devices is largely pentode in character, with a small linear
ohmic region and a large saturation region. I am interested
in expansion of the ohmic region, which is do-able with
power JFETs. You see devices like this in satellite and radar
applications, but even then you could not say they were
developed with audio in mind.

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Old 26th March 2010, 04:09 AM   #42
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Quote:
Originally Posted by Nelson Pass View Post
I am mostly interested in the transfer curves - the relationship of Ids, Vgs and Vds. The current crop of FET
devices is largely pentode in character, with a small linear
ohmic region and a large saturation region. I am interested
in expansion of the ohmic region, which is do-able with
power JFETs. You see devices like this in satellite and radar
applications, but even then you could not say they were
developed with audio in mind.
This is just what we see for the rare 2SK60 SIT transistors. Could you tell us what maximum values of Vds, Ids, Ciss, Rd, j-c thermal resistance are targeted at this part design?
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Old 26th March 2010, 08:49 AM   #43
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Nelson,
How might low tempco rank on your priorities?
Either way, extremely interested to see what brews...
Best wishes
cv
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Old 26th March 2010, 10:14 AM   #44
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I would guess the "beast with a thousand jfets" philosophy may work. Most FETs are many cells of small FETs paralelled together anyway. Just build 1000 2sk170 or 2sj74s on the same die??? Simple complementary power JFETs
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Old 26th March 2010, 04:00 PM   #45
flg is offline flg  United States
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Sometime back in the Blowtourch thread I think, Pavel M. did some simming and analysis of distortion with JFETs and it showed that short channel, equal length S and D with ideal Lamda proved the best peforming. I suppose that would apply here??? Probably to late to help NP even if I could.
Pavel's Instrument www site has the anaysis. It,s a bunch easier than the BT thread. I,m on my phone or I,ld go find it
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Old 26th March 2010, 04:26 PM   #46
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You might be right there Lee...that Mr. Pass' "1k jfet beast" is an exercise/r&d to get the signature sound of low noise small signal jfets into his custom power jfet...
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Old 26th March 2010, 06:54 PM   #47
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The usual jfets, 2sk170 and 2sj49 are actually more like
pentodes in character.

Short channel is the way to avoid saturation, but it does not
address popular applications. We are talking about eccentric
parts and usage.

Tempco? We'll see what we have when the parts are done.

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Old 10th January 2013, 11:29 PM   #48
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So what?

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Old 21st January 2013, 05:59 PM   #49
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Sorry OT, regiregi22 your pm box is full.
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