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Old 21st June 2012, 12:55 AM   #561
lhquam is offline lhquam  United States
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Default Kink in plots understood

It turns out that all of the plots I have shown with "kinks" in them at high power levels were underbiased. Ie. there was no current thru the diodes at the quiescent state. Dumb and dumber. I had neglected to look at the diode currents in addition to the total currents through the MOSFETs.

The rightmost plot in post #560 does have 30mA through the diodes, and .925A through the MOSFETs.

With actual tests (not SPICE) I have found that a bias of about 1.25A through the MOSFETs is needed to get the THD below .005%. The voltage across the 0R5 source resistors is about 0.525 volts.
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Old 21st June 2012, 01:00 AM   #562
lhquam is offline lhquam  United States
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Default Enough interest in a new thread?

Is there enough interest in this analysis of the F5 Turbo to fork off a new thread titled something like:

F5 Turbo Analysis, Simulation and Measurement

Or have we beaten the subject to death?
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Old 21st June 2012, 01:11 AM   #563
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I think it is time for people to start building and doing real measurements and together tweak this for optimum performance. I want to finish BA-3b first though
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Old 21st June 2012, 01:17 AM   #564
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I have one have finished, but I am in the middle of testing fets and going on vacation next week. Ilquam will have some of the matched pairs to test by weekend, so maybe we will have something to compare to simulation.
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Old 21st June 2012, 01:31 AM   #565
lhquam is offline lhquam  United States
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Quote:
Originally Posted by buzzforb View Post
I have one have finished, but I am in the middle of testing fets and going on vacation next week. Ilquam will have some of the matched pairs to test by weekend, so maybe we will have something to compare to simulation.
I am making live measurements of a balanced 1/2 Turbo. By 1/2 Turbo I mean it has one MOSFET per rail and one MUR1510 diode per FET. Here is an image of the board and is attachment to 1/2 of a HeatsinkUSA 10.08" x 7" heatsink:
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File Type: jpg DSC_0341.jpg (246.1 KB, 515 views)
File Type: jpg DSC_0342.jpg (244.1 KB, 515 views)
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Old 21st June 2012, 01:36 AM   #566
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Very nice. How do the measured numbers compare to simulated ones?
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Old 21st June 2012, 01:53 AM   #567
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Originally Posted by Melon Head View Post
I think it is time for people to start building and doing real measurements and together tweak this for optimum performance. I want to finish BA-3b first though
Agreed , Boards .......?
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Old 21st June 2012, 01:53 AM   #568
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Got two pairs
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Old 21st June 2012, 02:15 AM   #569
a.wayne is offline a.wayne  United States
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Need 4pr min /ch to fill my desires ....
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Old 21st June 2012, 02:16 AM   #570
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Agreed , Boards .......?
Maybe we should get 10 prototype boards made and start testing. I am happy to point to point though if required. I alread have a turbo amp without diodes probably wouldn't take too long to put the diodes in.
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