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Old 18th March 2009, 10:12 AM   #11
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Quote:
Originally posted by flg
Love the doggy thing...
/OT

Do you mean my avatar?
She is my beloved dog, Nayma; My sister-in-law found her in Barcellona (Spain), when she was a puppy, alone, hungry and scared (some other stray dog was attcking her, and byte her in few points).
Some not-so-good person abandoned her.
I then went there to meet my sister-in-law (I'm Italian...) and brought her back at home with me.
She looks really close to a Rodhesian Ridgeback, but she isn't.

OT/

Ciao
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Old 18th March 2009, 12:29 PM   #12
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Another version.

back to the LTP as input stage, and following the moore2355 article I replaced the N channel source follower with a P channel mosfet, moving it in the lower leg.
THIS is the updated schematic.
Note that the signal to the P channel mosfet is taken from the inverting leg of LTP (actually not inverted...).

Ciao,
Giovanni
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Old 18th March 2009, 05:10 PM   #13
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Quote:
Originally posted by flg


The formula for C has a deltaV component right? How much delta in V is there when in follower topology? And, How much deltaV is there in common source and common gate?
Depends wether you are driving only a CCS, or a CCS in parallel
with an actual load. Doesn't take much change in a gate charge
or channel current to do nothing, but swing volts against a CCS.

But to swing any Voltage against an 2~16 ohm load is something
that will require a change in channel current. Thus a change in
gate charge is always required, or nothing happens.

I believe the change in gate charge for a change in channel
current is the same, wether its an anode follower or source
follower. Only differences belonging to Miller effect as seen
at the Drain. Gate to source capacitance has to be charged
one way or another, no way around it.

---------------------------------

As for the most recent Croc effort, you can simplify the coupling
between the drain of Q4, the load, and Aleph, to two resistors.
And totally get rid of the coupling cap in the process.

Direct couple Q4's drain to the emitter of Q3.

Replace R16 (0.47R) current sensing resistor
with a series pair of 0.22R, basically splitting
R16 in two equal halves...

Connect the load in the middle of the totem.
Right between the eyes. (The series resistor
pair, I mean.)

Now ditch R3, R5, R10, C2.
Don't need em anymore.

See thread: "Possible improvements for Aleph?"
further details and explanation of this topology.

I also have a Hybrid Zen + Aleph schematic
posted there. Needing only a DC servo like
yours to be complete. I may need some help
with that part.
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Old 19th March 2009, 03:13 AM   #14
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Hi Giovanni,

I'm looking at your hybrid in the post#12, with interest. I could understand how it works. But not fully. About 80% . . . ? And, I'm how Q4 gets the bias voltage. How . . . ?

Tks.

><
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Old 19th March 2009, 08:03 AM   #15
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Quote:
Originally posted by Babowana
Hi Giovanni,

I'm looking at your hybrid in the post#12, with interest. I could understand how it works. But not fully. About 80% . . . ? And, I'm how Q4 gets the bias voltage. How . . . ?

Tks.

><

The op-amp is there for that purpose.
The OP07 is a DC servo, which will bias Q4 in manner to maintain (talking about DC condition) 0V at the output.
Please refer to
THIS article from the TubeCAD.

Ciao
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Old 19th March 2009, 08:10 AM   #16
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Quote:
Please refer to THIS article from the TubeCAD.
By the way, I found the article only today, then after I drawn the schematic...
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Old 19th March 2009, 08:45 AM   #17
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Back to your circuite. I believe that returning the feedback
to the grid is positive feedback makes a good ocilator!
Attached Files
File Type: pdf hybrid_002.pdf (34.6 KB, 119 views)
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Old 19th March 2009, 08:57 AM   #18
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The return to the input grid is a dead end.

If the tube circuit is well designed no NFB what so ever is needed. A 6N6 or 6H30 at 120V at 10mA or more is good enough.
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Old 19th March 2009, 09:43 AM   #19
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Noticed you where into the modulated-CCS thing. Maybe the NFB is needed then.

Two simplified versions of the driver:
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File Type: png drive.png (73.2 KB, 861 views)
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Old 19th March 2009, 10:30 AM   #20
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Quote:
Originally posted by croccodillo

Please refer to
THIS article from the TubeCAD.


Giovanni, thanks for the reference. It gives me a clear picture.

I was wondering why R13 was there. It seems that now I understand the reason. It is to keep very low dc voltage at the output of the servo, and by doing so, to make the dc offset at the amp's output "drift vertually at 0V", isn't it?

Ciao,

><
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