Jfet F1

bappe · 3rd January 2006, 08:35 AM

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?
Comments?

Zoran · 3rd January 2006, 09:31 AM

Hi
I spot that You are using the JFET element
in Your schematic...
Do You have a spice model for the LU1014 maybe?
Thanks.

bappe · 3rd January 2006, 10:32 AM

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

lineup · 3rd January 2006, 10:59 AM

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

bappe · 3rd January 2006, 11:02 AM

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

lineup · 3rd January 2006, 11:10 AM

Okay
a negative supply -3V

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

3rd January 2006, 09:31 AM	#2
Zoran diyAudio Member Join Date: Jan 2004 Location: Belgrade	Hi I spot that You are using the JFET element in Your schematic... Do You have a spice model for the LU1014 maybe? Thanks. __________________ ###

3rd January 2006, 10:32 AM	#3
bappe diyAudio Member Join Date: Sep 2002 Location: Furulund, SWEDEN	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

3rd January 2006, 10:59 AM	#4
lineup diyAudio Member Join Date: Dec 2005 Location: the north	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 __________________ lineup

3rd January 2006, 11:10 AM	#6
lineup diyAudio Member Join Date: Dec 2005 Location: the north	Okay a negative supply -3V To me it looks like symbol for a positive supply I guess this did confuse me ... __________________ lineup

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3rd January 2006, 11:02 AM	#5
bappe diyAudio Member Join Date: Sep 2002 Location: Furulund, SWEDEN	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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