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spgjmf 18th August 2010 11:56 PM

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,

Nelson Pass 19th August 2010 04:03 AM

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.


spgjmf 19th August 2010 05:40 PM

Thanks Mr. Pass,

I returned to the bench to toy with the circuit and found, to my horror,:eek:
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...


spgjmf 20th August 2010 03:55 PM

just to wrap it up...

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


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