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Old 20th November 2007, 07:54 PM   #231
EUVL is offline EUVL  Europe
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> One could use a separate, more negative supply on the 'J109's drain R, maybe just hooked off with a zener or TL431...

Doesn't any ripple voltage (or noise) between this "more negative supply" and the "normal" negative rail gets directly magnified in the 2nd stage, i.e. 0dB PSRR ?


Patrick
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Old 20th November 2007, 08:11 PM   #232
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Yes... so the dropped supply must be very clean. I think a shunt reg, properly bypassed to R18/19, would do it. With adjustable offsetting one could also optimize the LTP current and output offset independently, even open-loop gain (via R7). Not shure if this would still be an Aleph-J, though.

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Old 20th November 2007, 08:32 PM   #233
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another brilliant idea



EDIT :

I forgot that I need P type LU for that
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Old 20th November 2007, 09:03 PM   #234
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very interesting and very promising so far.
keep it up.

SandMarc
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Old 20th November 2007, 09:13 PM   #235
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Quote:
Originally posted by sandmarc
very interesting and very promising so far.
keep it up.

SandMarc
yup-as follower .........


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Old 21st November 2007, 05:28 AM   #236
EUVL is offline EUVL  Europe
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> another brilliant idea
> I forgot that I need P type LU for that

I am stupid this morning.
Explain to me how you might get +1V Vgs on your P-type LU (or if you flip it, then -1V Vgs on LU1014) to get the triode curve ?

> keep it up.

It is perhaps time you get your own brain to do some work ......


Patrick
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Old 21st November 2007, 07:57 AM   #237
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Quote:
Originally posted by EUVL
> another brilliant idea
> I forgot that I need P type LU for that

I am stupid this morning.
Explain to me how you might get +1V Vgs on your P-type LU (or if you flip it, then -1V Vgs on LU1014) to get the triode curve ?

> keep it up.

It is perhaps time you get your own brain to do some work ......


Patrick

Patrick

I know that you are stupid , so there is no need to say that in public ;

for me - name of the game is fun , not "smartyfarty" ;

I'm not here for contest .

you are looking at trivia in that schmtc , even if entire schmtc is trivial
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Old 21st November 2007, 08:02 AM   #238
EUVL is offline EUVL  Europe
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> I know that you are stupid , so there is no need to say that in public

I have no problem admitting that in public.

> I'm not here for contest

Neither am I.


It was a legitimate question.

The entire difficulty of using LU1014 in the circuit IS the negative Vgs.
I had a second look just now and still could not figure out how your proposal would solve that.
So perhaps you can enlighten me.


Patrick

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Old 21st November 2007, 10:35 AM   #239
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Quote:
Originally posted by EUVL
> I know that you are stupid , so there is no need to say that in public

I have no problem admitting that in public.

> I'm not here for contest

Neither am I.
so - welcome to the club of smart ones , so we can continue with fun......

Quote:

It was a legitimate question.

The entire difficulty of using LU1014 in the circuit IS the negative Vgs.
I had a second look just now and still could not figure out how your proposal would solve that.
So perhaps you can enlighten me.


Patrick

it was legitimate question , but it was also more than obvious that I made mistake connecting G-S of LU ( that line probably was just intention to draw bracket for pointing voltage G-S , or just brain glitch ..... whatever )

input LTP is nothing else than tube LTP and LU is nothing else than top tube in output tube cascode ........biasing LU is achieved with biasing input LTP ......... pretty common way of DC coupling two stages in tube world ........

anyway - nothing of that is important really ; what is - is that I drew follower with LU , not active stage ......

it can be done like this , but with full swing stage in middle , and I don't wanna do that.
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Old 21st November 2007, 11:42 AM   #240
EUVL is offline EUVL  Europe
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Choky,

I think you are still missing my point.
Put the +ve rail on the bottom, and you almost get back to Nelson's schematics.

The voltage across the drain resistor of the diff pair is something like 4V ABOVE negative rail. If we stick to a source resistor of 0R68 for the LU1014, AND you want it to work in the triode region, then the current through the 0R68 is something like (4+1)V/0R68 = 7.3A. That is likely to kill your 1014.

In ZV9, the gate of the 1014 is at 0V nomimal. But because there is a bias of about 1.3A, the 0R68 will have 1V drop across it, makeing the source at 1V nominal. Thus, Vgs is about -1V.

Any modification of the A-J schematic to use the 1014 has to be able to offer this -1V Vgs before it will work as intended. My proposed solution with the 4mA CCS diode is intended to drain all the DC current of the diff pair so that there is no DC current across the drain resistors, i.e. Vg at negative rail voltage. The rest is then like ZV9, but referenced to the negative rail.

Hope we are still not talking over each other.


Patrick
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