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how about using J111 J175 Jfets in F5
how about using J111 J175 Jfets in F5
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Old 29th December 2017, 11:16 AM   #41
Nag is offline Nag  India
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For example if my JFETS are j113 & j176 have Idss about 35mA. So now How can I reduce it 8ma to 10ma bias with paralleling or in series. I read about cascoding article and honestly I don't have that much basic knowledge to process that information in that article.
thanks.
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Old 29th December 2017, 11:23 AM   #42
Zen Mod is online now Zen Mod  Serbia
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how about using J111 J175 Jfets in F5
majority of investment in amplifier is going to heavy hardware - xformer , caps , case with heatsinks ;

regarding how big decrease in performance and how small amount of saved greenies , if using any other JFets than prescribed , it's simply not wise to proceed with anything else than real thing

even taking in account that for someone obtaining them is complicated , not just or nothing at all matter of money

If you can't manage to have proper JFets , build some another amp , where you can substitute them much easily ....... or some other amp without JFets
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Old 29th December 2017, 11:33 AM   #43
Nag is offline Nag  India
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Quote:
Originally Posted by Zen Mod View Post
majority of investment in amplifier is going to heavy hardware - xformer , caps , case with heatsinks ;

regarding how big decrease in performance and how small amount of saved greenies , if using any other JFets than prescribed , it's simply not wise to proceed with anything else than real thing

even taking in account that for someone obtaining them is complicated , not just or nothing at all matter of money

If you can't manage to have proper JFets , build some another amp , where you can substitute them much easily ....... or some other amp without JFets
Yeah right. But some newbies want economy build to dirt their hands for first time builds. Cost is too high after shipping and customs for linear systems jfets. May be Mr. Nelson or someone has some secret circuit for guys like me. If I ask only then Members will provide different ways. I have another project PLH in mind because of absolute parts of Toshiba. any exicon lateral or irf available replacement for irf610 to build PLH ?.
Thank you.

Last edited by Nag; 29th December 2017 at 11:47 AM.
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Old 29th December 2017, 11:54 AM   #44
Zen Mod is online now Zen Mod  Serbia
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how about using J111 J175 Jfets in F5
build Babelfish J - using J271 for input LTP and pretty much any IRFP N- channel for output

you can make it even on veroboard or PtP ...... or you can make your own pcbs from pdfs posted in first (old ) thread


instead of IRF610 you can pretty much use any of these - IRF510 , 520, 530 , 610,620,630

higher the number , higher voltage and higher capacitances
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Old 29th December 2017, 04:25 PM   #45
Nelson Pass is offline Nelson Pass  United States
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how about using J111 J175 Jfets in F5
Quote:
Originally Posted by Nag View Post
But some newbies want economy build to dirt their hands for first time builds.
J76 and J113 are the most likely candidates for this - lower Idss.

You would have to adjust the Source resistors to get the currents into the
right range, and it might be a little funky, but it will work.
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Old 29th December 2017, 04:48 PM   #46
indra1 is offline indra1  Indonesia
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Quote:
Originally Posted by Nag View Post
. . . . May be Mr. Nelson or someone has some secret circuit for guys like me. . . . .
While funky is great, you could also try the 2SJ104BL and 2SK364BL pair for comparable spec but the low noise attribute.
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Old 29th December 2017, 05:42 PM   #47
Nag is offline Nag  India
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Quote:
Originally Posted by Nelson Pass View Post
J76 and J113 are the most likely candidates for this - lower Idss.

You would have to adjust the Source resistors to get the currents into the
right range, and it might be a little funky, but it will work.
Thank you Mr. Nelson. long search for quest ended here.
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Old 29th December 2017, 06:58 PM   #48
Mark Johnson is offline Mark Johnson  United States
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how about using J111 J175 Jfets in F5
Quote:
Originally Posted by Nelson Pass View Post
J76 and J113 are the most likely candidates for this - lower Idss.
I suspect there is a typo above, and Nelson actually means the J176 P-channel JFET whose datasheet (attached here) specifies
2.0 mA <= |Idss| <= 25 mA
The J177 has even lower Idss, but DigiKey doesn't sell it as a thru-hole part, only surface mount. Fortunately the DIY-focused vendor "Linear Systems," does sell it in thru-hole.

_
Attached Files
File Type: pdf J174_SST174_P-Channel,_Single,_JFET_Switch.pdf (257.9 KB, 27 views)
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Old 30th December 2017, 02:38 AM   #49
Nag is offline Nag  India
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Quote:
Originally Posted by Mark Johnson View Post
I suspect there is a typo above, and Nelson actually means the J176 P-channel JFET whose datasheet (attached here) specifies
2.0 mA <= |Idss| <= 25 mA
The J177 has even lower Idss, but DigiKey doesn't sell it as a thru-hole part, only surface mount. Fortunately the DIY-focused vendor "Linear Systems," does sell it in thru-hole.

_
J176 has higher dissipation rate than J177(260mw). J113 & J176 have around 360mw power dissipation.
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Old 31st December 2017, 06:42 PM   #50
Nelson Pass is offline Nelson Pass  United States
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how about using J111 J175 Jfets in F5
Quote:
Originally Posted by Mark Johnson View Post
I suspect there is a typo above, and Nelson actually means the J176
P-channel JFET whose datasheet (attached here) specifies
2.0 mA <= |Idss| <= 25 mA
Actually, measuring my extensive population of these parts,

probably should have said J175.

The J113's come in at around 20-40 mA.

The J175's are 25-30, J176 are 8-15, and P1086 are 20-30.

Regardless of the spec in the old datasheet, this is what I'm seeing.

Getting matches for these is not easy, and for the F5 adjustment of Source
and Drain resistors will be necessary to get a balance.
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