JfetBOZ mods

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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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Official Court Jester
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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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carpenter said:
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?
 
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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Carpenter, I'm not sure what your trying to do :confused: 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 :D
 

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flg said:
Carpenter, I'm not sure what your trying to do :confused: 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 :D


Sweet. It reminds me a little of the original Zen amp dressed up in Jfets.:) :) :) How about posting some values?

As far as what I'm trying to do--I'm exploring!:D
 
yggdrasil said:
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.


I like your drawing and the fact that you're using the DIY Op-amp tutorial. I must review.:)
 
yggdrasil said:
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.


What happens when you raise, or lower, the value of R5? Raising R5 should increase the voltage over the Jfet, placing it closer to the center of the available voltage--this would increase the voltage swing?
 
Formerly "jh6you". R.I.P.
Joined 2006
carpenter said:
Does it become a current gain device?



I'm not a pro. Still a baby asking lessons from Papa.

Anyhow, we already know that V=IR (dc or ac). When the R is a
fixed value, the V could be changing depending on only the
variations of the I. Here, if the V is to be the amplified voltage,
we need to provide the varying currents, with certain devices--
transistors or field effect transistors (FETs).

But, at the source of the FET, if we have the CCS (constant
current sink), it will limit the current variations which we need for
the amplified V.

Yes . . . I think all TRs and FETs are current gaining devices . . .



:darkside:
 
carpenter said:



What happens when you raise, or lower, the value of R5? Raising R5 should increase the voltage over the Jfet, placing it closer to the center of the available voltage--this would increase the voltage swing?
Yes, but it would also increase the voltage at the source and reduce current bias.


Babowana said:

But, at the source of the FET, if we have the CCS (constant
current sink), it will limit the current variations which we need for
the amplified V.
Are you sure this isn't the case if you replace the drain resistor with a ccs?
 
Diy Audio is certainly looking festive!:D

I tried the CCS in my drawing; it required the same resistor values as the original JfetBOZ to operate properly.

So what did I gain?

Less than zero: the golden ears in my family didn't like the CCS at all (at least in its current implementation)--I'll try Choky's idea of dual voltage rails for kicks later. In fact, my sweetie thinks I'm nuts for toying around with what she thinks is perfection (Nelson's original layout). I told her I'm trying to learn through experimentation--she thinks I'm an idiot and should leave well enough alone...:clown: :rolleyes: :(

Obviously, I have mixed emotions.........
 
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