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Old 18th August 2010, 11:56 PM   #1
spgjmf is offline spgjmf  United States
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Default jboz J310, 12volts, question about Drain R

hi folks,
I have some J310 fets and want to use them for a jboz preamp. I'd like to run them on 12 volts. the j310 schema I found here has 24volt PS. the drain R is 2.2K. What would the best value of Drain R be for 12volt operation?

I tried 1k and it got loader Sources R is 560ohm...

thanks for any ideas,
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Old 19th August 2010, 04:03 AM   #2
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Join Date: Mar 2001
It's largely a question of what the Jfet is bias at. If the bias
current is 10 mA, then 560 ohms will put the DC near the
center of the supply.

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Old 19th August 2010, 05:40 PM   #3
spgjmf is offline spgjmf  United States
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Join Date: Jan 2008
Thanks Mr. Pass,

I returned to the bench to toy with the circuit and found, to my horror,
I had used the jboz 2sk170 values for the J310 jboz...

that would explain the lack of function....I'll give it a go
with the correct values.

need to find a FET 101 book...

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Old 20th August 2010, 03:55 PM   #4
spgjmf is offline spgjmf  United States
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Join Date: Jan 2008
just to wrap it up...

I used 680ohm on the drain and 220ohm on the source - all is well.

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