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Beast with 1000 JFETs redux ?
Beast with 1000 JFETs redux ?
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Old 21st January 2021, 10:09 PM   #181
woofertester is offline woofertester  United States
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Thank you Biosonar for that info. It helps enormously.

I have thought that the J113/J175 version should have source resistors for power dissipation reduction. Now I will start a PCB for that configuration.

While we are talking about the J113, my datasheet shows gate at the left-most pin. The actual JFET has gate at the right-most pin. What is the deal with that?

For Idss, my J113 devices are all between 14mA and 28mA. I have tested hundreds. I bought a bag of 1000. Slowly working my way through them.

My J175 devices are between 20mA and 24mA. I have tested 100. More are on the way.

My assertion is that the combined Idss of each 1/2 of the buffer must match. The parallel buffer elements are all connected at the output.

So, there will be a PCB for un-degenerated FJETs like the J270 and 2SK304. That pcb is on the way to me. There will be a pcb for degenerated JFETs like the J113 and J175.
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Old 22nd January 2021, 12:00 AM   #182
Biosonar is offline Biosonar  United States
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Here is another possibility for CCS mini-beast using the Toshiba 2Sk209 GB jfet. This design was suggested by Wayne from Pass Labs. Remove R4, R5 and add a gate resistor to the input:
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Old 22nd January 2021, 12:20 AM   #183
woofertester is offline woofertester  United States
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Quote:
Originally Posted by Biosonar View Post
Here is another possibility for CCS mini-beast using the Toshiba 2Sk209 GB jfet. This design was suggested by Wayne from Pass Labs. Remove R4, R5 and add a gate resistor to the input:
I agree that a 2SK209/2SK208/2SK2145 massive B1 is a great idea. The trough-hole version is first on my list to build. The surface mount version for me will have to be assembled at a contract manufacturer.

Rochester has good candidates for through-hole JFETs. I have ordered some to evaluate. I will also build J113/J175 through-hole versions.
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Old 22nd January 2021, 03:59 PM   #184
woofertester is offline woofertester  United States
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After new information from Biosonar, I have changed the basic cell. Here is the schematic.

I have added G-D-S transistors. The original transistors are D-G-S. Now the builder can choose D-G-S devices or G-D-S transistors. You can choose one of each.

The J113 is D-S-G and the J175 is D-G-S. These two can be used with this new board.
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File Type: jpg BufferV4_schematic.jpg (140.5 KB, 295 views)

Last edited by woofertester; 22nd January 2021 at 04:02 PM.
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Old 22nd January 2021, 05:11 PM   #185
woofertester is offline woofertester  United States
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Here is the PCB.
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File Type: jpg BufferV4.jpg (801.0 KB, 281 views)
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Old 23rd January 2021, 08:45 PM   #186
woofertester is offline woofertester  United States
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Default B1 Mini Beast

Both D-G-S and G-D-S pinouts are supported on this Mini B1 Beast

I am sorting the JFETs I have and have ordered additional types to characterize.

You can also use all P-JFETs if you reverse the power supply polarities. Aye, Keptin. Reverse the polarities.
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File Type: jpg B1_Beast_schematic.jpg (218.3 KB, 248 views)
File Type: jpg Mini_B1_Beast_3D.jpg (799.4 KB, 250 views)

Last edited by woofertester; 23rd January 2021 at 08:49 PM.
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Old 23rd January 2021, 08:52 PM   #187
mhenschel is offline mhenschel  Canada
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Sounds like "reworse".
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Old 24th January 2021, 11:14 PM   #188
woofertester is offline woofertester  United States
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Default Series B1 for extended voltage?

I have found a surplus JFET that is reasonably priced and has good gm and low noise. The limiting factor is that the device max voltage is 15v. If I want to use + / - 15v rails, is this a reasonable approach for the basic cell?
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Old 25th January 2021, 12:04 AM   #189
Zen Mod is offline Zen Mod  Serbia
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Beast with 1000 JFETs redux ?
well, not exactly

when you put more than one CCS in chain, there goes trouble

go here and download some reading material: Erno Borbely site , zip file - for benefit of DIY community - Zen Mod Blog

cascode them with bjts, shown in numerous Papa's thingies, same as in SissySIT etc.
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Old 25th January 2021, 01:21 AM   #190
woofertester is offline woofertester  United States
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Quote:
Originally Posted by Zen Mod View Post
well, not exactly

when you put more than one CCS in chain, there goes trouble

go here and download some reading material: Erno Borbely site , zip file - for benefit of DIY community - Zen Mod Blog

cascode them with bjts, shown in numerous Papa's thingies, same as in SissySIT etc.
Ok Thanks. Will do.
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