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Old 15th December 2007, 09:10 PM   #1
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Default JfetBOZ mods

Moderators, please feel free to relocate this as you see fit.


I'm thrilled with my JfetBOZ. It's currently acting as a line-stage in front of my F4.

Of course, Nelson has given us many examples of how to modify, and (hopefully) improve a circuit. I'm going to breadboard this CCS to my JfetBOZ. I thought I'd share my idea; perhaps someone out there has thoughts or suggestions they'd like to put forth.
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Old 15th December 2007, 09:38 PM   #2
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it's easier , better because of bigger dynamic resistance (maybe even better noise -wise) to implement other sort of CCS .......... say - CCS from toob boyz P10, Geek and others , or two bjt ccs which you can see in Bab and Pumpy .

besides that - if you want to use CCS there - you'll either lift source of jfet too high , or bottom CCS .......... same thing called with different names ......

point is that jfet need adequate voltage between S and G for defined current ; CCS need some voltage to breath , and that's certainly not so small voltage - which Jfet need between S and G .........

so - conclusion - Jfet gate stays at gnd potential , but tail of CCS must go lower ...............on negative voltage


look at ccswhatever bosoz , cascoded or not and than say what you saw


EDIT:

well - I didn't even mention gain issue .........etc

maybe is better to relocate CCS up , and then - choosing adequate source degeneration resistor ........ set desired gain
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Old 15th December 2007, 10:21 PM   #3
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Looks like I have more homework.
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Old 15th December 2007, 10:34 PM   #4
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Quote:
Originally posted by carpenter
Looks like I have more homework.

go to last third of Pumpy developing/amusing/musing/maki'funofit thread and look for schematic of thing, with voltage values in it ;
I drew that for crazy danske Lykkkkkkk , one of many times when he was in trouble .

there you can see few important things ;
or you can try Papa's cascode pdf
or you can go to Borbely's and look for his papers regarding line stages ...... "...frontiers" stuff .

are you familiar with toobz?
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Old 15th December 2007, 10:44 PM   #5
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Quote:
are you familiar with toobz?
more legs?

Carpenter, Is your intention to use a jfetBOZ variation as your preamp for your F4?
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Old 15th December 2007, 11:41 PM   #6
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Quote:
Originally posted by mpmarino


more legs?

Carpenter, Is your intention to use a jfetBOZ variation as your preamp for your F4?

I need it more as a line/gain stage. I have a receiver for home theater/Dolby and such. The Jfet BOZ is an interface.
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Old 16th December 2007, 12:28 AM   #7
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I haven't yet come to the Jfet Boz. Too many other projects, but getting closer.

Anyway in the DIY opamp paper Nelson Pass show a simple bjt ccs.

I put it in the Jfet Boz circuit instead of the source resistor. The sims give the same voltages and currents as with the resistor.
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Old 16th December 2007, 01:40 AM   #8
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Quote:
I need it more as a line/gain stage. I have a receiver for home theater/Dolby and such. The Jfet BOZ is an interface.
Cool .. I'm sure you'll make it work nicely
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Old 16th December 2007, 01:59 AM   #9
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Quote:
Originally posted by yggdrasil


I put it in the Jfet Boz circuit instead of the source resistor.


If you replace the source resistor with CCS,
the Jfet will not work as a voltage gain device.


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Old 16th December 2007, 02:44 AM   #10
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Carpenter, I'm not sure what your trying to do But, I've been building up the thing below. It's nothing new but it has the capability of enough voltage swing to drive an F4... Or, provide line level voltage swings with great headroom
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