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Old 3rd January 2006, 09:35 AM   #1
bappe is offline bappe  Sweden
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Default Jfet F1

Hi all!

Being a full range sucker since the dawn of time, the F1 really appealed to me, what did not though was the use of MOSFET´s. They (the MOSFET´s) have constantly failed to amaze me over the years, this might be because i have never tried any PASS amps? I first started to look at doing someting like the F1 but with BJT´s but then the power jfet entered the stage, thanks Nelson! I am now in the process of obtaining a few samples of the LU1014D to make someting like what you can see in the picture.
Anyone having the same thoughts?
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Old 3rd January 2006, 10:31 AM   #2
Zoran is offline Zoran  Serbia
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Hi
I spot that You are using the JFET element
in Your schematic...
Do You have a spice model for the LU1014 maybe?
Thanks.
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Old 3rd January 2006, 11:32 AM   #3
bappe is offline bappe  Sweden
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Default LU1014 pspice

I´m using this model for now, it has a good enough fit. You can fiddle a bit with beta to get the correct dc bias point.

.MODEL LU1014D NJF (VTO=-1.8 BETA=1.7 LAMBDA=0.7 RD=0.0065 CGD=363P CGS=784P VTOTC=-2.6M)

BR,
Anders
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Old 3rd January 2006, 11:59 AM   #4
lineup is offline lineup  Sweden
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you would expect all current goto Ground.
But after Q7 it all goes into V41.
It looks as a voltage supply.

I can not understand what V41 is
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Old 3rd January 2006, 12:02 PM   #5
bappe is offline bappe  Sweden
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Correct!
Since i want the input to sit at 0V that leaves nothing to Q7, hence the -3V supply. This might not be the final solution though.

/Anders
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Old 3rd January 2006, 12:10 PM   #6
lineup is offline lineup  Sweden
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Okay
a negative supply -3V

To me it looks like symbol for a positive supply
I guess this did confuse me ...
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