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Old 26th June 2012, 04:33 PM   #531
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Okay, I'll show you something: Please have a look here and here.
Now it's your turn.
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Old 26th June 2012, 06:16 PM   #532
Waly is offline Waly  United Kingdom
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Quote:
Originally Posted by Edmond Stuart View Post
Okay, I'll show you something: Please have a look here and here.
Now it's your turn.
Sorry, I was not born in the 70's and don't know what a tape recorder is.

Here is one of mine, about 10,000 mosfets on the analog side (including analog switches and CCDs).

Let me know when you have something (with discretes) belonging to the 21st century.
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Last edited by Waly; 26th June 2012 at 06:19 PM.
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Old 26th June 2012, 10:41 PM   #533
KSTR is offline KSTR  Germany
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Originally Posted by wahab View Post
Well , your design is about 3.2R mini impedance that can dip
below 1R according to your numbers due to magnetic saturation
but then what will be the max current once your LCR network
is adapted ?..
Our student trainee will hopefully complete the new xover boards by tomorrow, then it's time to measure (and listen) again... we also advised him to arrange the component layout to avoid any magnetic coupling between the various coils -- by actually measuring in search for minimized coupling before mounting (again an issue that is often seen even in professional high-end speakers).
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Old 26th June 2012, 11:24 PM   #534
Bonsai is offline Bonsai  Taiwan
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How many of the IP blocks did you personally create, optimize and compact for optimum performance? Now that would be interesting and I am sure we could share some good ideas.
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Old 26th June 2012, 11:26 PM   #535
Bonsai is offline Bonsai  Taiwan
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Originally Posted by KSTR View Post
Our student trainee will hopefully complete the new xover boards by tomorrow, then it's time to measure (and listen) again... we also advised him to arrange the component layout to avoid any magnetic coupling between the various coils -- by actually measuring in search for minimized coupling before mounting (again an issue that is often seen even in professional high-end speakers).
Is that Waly by any chance?
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Old 27th June 2012, 09:09 AM   #536
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Default Output speed?

Any one still remember Edmond's front end
Well I still need an OPS for it and I have a question.
How close to minimum phase is a BJT near Ft?

In the LTSpice help they call TF the "transit time"
If it is a real time delay then behaviour near Ft will depart from minimum phase.
If TF is just the time constant of the frequency roll-off then it will be close to minimum phase.
So a second question would be -
How close is SPICE to real transistor behaviour in this area?

This puts an upper limit on loop stability so it's fairly important for optimized compensation.

Best wishes
David

Last edited by Dave Zan; 27th June 2012 at 09:13 AM.
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Old 27th June 2012, 09:50 AM   #537
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Hi David,

Did you read these comments , where I stated that a clear distinction should be made between time delay and phase lag? Or is it just a coincidence?

As for your question, you can figure it out by observing the delay in onset of a step response. BTW, "transit times" as published in most data sheets are not very helpful, because the tranny is used as a switching device, thus not as a linear amplifier, which makes a large difference (comparable to TTL vs ECL logic).

Cheers,
E.
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Old 27th June 2012, 10:31 AM   #538
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Originally Posted by Edmond Stuart View Post
Hi David,

Did you read these comments , where I stated that a clear distinction should be made between time delay and phase lag? Or is it just a coincidence?
No, just a coincidence. I did not ask in the context of feedback at audio frequencies, as in your discussion, I know that stuff. I am interested in how far the unity crossover frequency can be increased. There is a clear difference between a minimum phase roll off, that can be equalized, and a time delay, that can't.
A pity that Bob Cordell uses the term "excess phase" rather loosely in his book. It would have been a chance to present a concept that is so frequently misunderstood, as your link shows.
Dennis Feucht wrote an article that seems to imply transistors are not minimum phase near Ft. Since he seems pretty sharp I take it seriously.

Quote:
As for your question, you can figure it out by observing the delay in onset of a step response.
An ONsemi NJL4*** has 35 MHz Ft so it would need nanosecond resolution to be accurate. Equipment to do measurement at that speed is not DIY level. I hoped some of the people here who do electronics professionally would have the information.

Best wishes
David

Last edited by Dave Zan; 27th June 2012 at 10:38 AM.
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Old 27th June 2012, 10:38 AM   #539
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>An ONsemi NJL4*** has 35 MHz Ft so it would need nanosecond resolution to be accurate. Equipment to do measurement at that speed is too expensive for me.

But you may figure out how a simulator deals with it, i.e whether it's treated as phase shift or as propagation delay.
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Old 27th June 2012, 10:45 AM   #540
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Originally Posted by Edmond Stuart View Post
But you may figure out how a simulator deals with it, i.e whether it's treated as phase shift or as propagation delay.
To determine what SPICE does I plan simply to plot the frequency response and compare the phase with the amplitude slope. I am a Bode kind of bloke But I still need to know what a transistor really does.

Best wishes
David

Last edited by Dave Zan; 27th June 2012 at 10:48 AM.
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