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Old 17th December 2008, 04:04 PM   #11
wg_ski is offline wg_ski  United States
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Quote:
Originally posted by lineup


Lineup Quattro Output Stage
.. just invented

high gain super plus!!!!
Looks a lot like the Bryston Quad-complementary.
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Old 17th December 2008, 04:15 PM   #12
wg_ski is offline wg_ski  United States
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Default Re: Triple emmiter follower

Quote:
Originally posted by bogdan_borko
Is this simulation problem real and could this be fixed without using output coil ,zobel and feedback?

Thanks.
Borko.
These outputs are usually quite stable, even without a zobel. Try getting rid of C4. With that cap, you can end up with switchoff problems. Every time I've used one in that position, I ended up getting rid of it because I didn't like the behavior at clipping.
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Old 17th December 2008, 04:20 PM   #13
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Quote:
Originally posted by lineup
Bonsai

Why settle for Tripple

When you can try the brand new

Lineup Quattro Output Stage
.. just invented

high gain super plus!!!!
No feedback allowed...
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Old 17th December 2008, 04:34 PM   #14
wg_ski is offline wg_ski  United States
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Quote:
Originally posted by bogdan_borko


No feedback allowed...

If no feedback is allowed, then technically you have to exclude darlingtons (double, triple, or even quad) as well.
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Old 17th December 2008, 04:35 PM   #15
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Quote:
In these cases the cause is almost always parasitic oscillation in the output stage
Yes ,I figured out that this is the problem source...
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Old 17th December 2008, 06:44 PM   #16
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Nico have you played with the circuit?
BTW the same problem ocured with double emitter follower...
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Old 17th December 2008, 07:03 PM   #17
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Quote:
Originally posted by bogdan_borko


Yes ,I figured out that this is the problem source...
I find that your circuit thermally it is not stable.

Put source 0V amplitude and then run transient with temperature setting 27,50 Now look at the current through emitter resistors.

You can also see this with V(OUT) at 27 deg, offset is a few millivolt, but at 50 degrees it is 10V

Regards

Nico
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Old 17th December 2008, 07:32 PM   #18
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Quote:
Originally posted by Nico Ras


I find that your circuit thermally it is not stable.

Put source 0V amplitude and then run transient with temperature setting 27,50 Now look at the current through emitter resistors.

You can also see this with V(OUT) at 27 deg, offset is a few millivolt, but at 50 degrees it is 10V

Regards

Nico
Well it`s just an example but thanks, I didn`t knew the trick.
What about the main problem?
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Old 17th December 2008, 07:39 PM   #19
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It would appear that the triple emitter follower has temperature stability issues. Lineup what is your opinion.

Nico
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Old 17th December 2008, 08:10 PM   #20
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Quote:
Originally posted by bogdan_borko


Well it`s just an example but thanks, I didn`t knew the trick.
What about the main problem?


I used the pulse stimulus and I do not see the oscillations you do, in fact the wave has a small over and undershoot. I am not sure for the reason C3, I used 1-10n or so between individual bases. In practice, obviously you will be applying NFB when used in circuit.

I do not have the same models as you since your models was not in the model page. I do not see the oscillations that you do.

We use a lot of On-Semi products and when I saw the comments that their models are unreliable, I contacted their support engineers and they assured me that there models are based on worst case scenario.

I was told that if I want to create models for individual transistors I can do it but that am making a big mistake. So I use their models as provided.

I hope I was of some help,

Nico
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