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Class D Switching Power Amplifiers and Power D/A conversion

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Old 24th November 2011, 12:12 AM   #1481
kubeek is offline kubeek  Czech Republic
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CPX, how does your power supply look like?
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Old 24th November 2011, 08:37 AM   #1482
CPX is offline CPX  Romania
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I have tested the prototype with transformer and switching power supply...the distorsions are the same..
It is clear now that switching noise is getting into the analog stage..but i do not understand why..
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Old 24th November 2011, 12:25 PM   #1483
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salut incearca sa pui in reteaua de reactie condensator polipropilena si rezistoare film metal 1%


hello try to place polypropylene capacitor and metal film rezistors in the feedback network
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Old 24th November 2011, 12:35 PM   #1484
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Update(5)
At higher frequencies i can get lower power before heavy distorsion begins.
I get 8 amps at 50 hz and 4 amps at 20khz max..it sounds like positive feedback but i tried every filtering method i could think of in the singal path with no succes...
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Old 26th November 2011, 07:06 PM   #1485
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Decreasing inductance increases the point(in Amps) where abnormal distorsion and noise begins.With 10uH that zone is near clipping at 18kz and 2 ohm load.With 1 ohm load and 15khz,18khz and beyond i still have problems and I do not want to decrease inductance any further.

distorsion begins here far beyond clipping level - 18khz 1 ohm load.
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distorsion begins here far beyond clipping level - 15khz 1 ohm load.
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distorsion begins here at clipping level for 18khz 2 ohm load
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no distorsion at clipping level for 18khz 4 ohm load
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So..as load impedance decreases and frequency increases heavy distorsion(white noise and lower frequency sounds) apear bofore clipping level..why?

Last edited by CPX; 26th November 2011 at 07:21 PM.
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Old 6th December 2011, 09:30 PM   #1486
CPX is offline CPX  Romania
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Question:
Do you think changing lm311 with lt1016 will decrease distorsions?
It has 10ns response time.
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Old 6th December 2011, 09:47 PM   #1487
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Quote:
Originally Posted by CPX View Post
Question:
Do you think changing lm311 with lt1016 will decrease distorsions?
It has 10ns response time.
Where exactly are these waveforms taken? Can you do an FFT?
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Old 6th December 2011, 09:50 PM   #1488
CPX is offline CPX  Romania
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The waveforms are exactly at the output..
Tomorow i will try to do a fft but i do not know if the noise will be visible on it.
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Old 7th December 2011, 07:20 AM   #1489
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Quote:
Originally Posted by CPX View Post
Question:
Do you think changing lm311 with lt1016 will decrease distorsions?
It has 10ns response time.
I use the TL3016 (lower cost from TI) version of this chip with great success in full-bridge designs. The LM311 is certainly a bit on the slow side. The TL3016 needs +/-5V supplies though, as it won't tolerate +/-12V rails. Check the data sheet before using it!
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Old 7th December 2011, 04:00 PM   #1490
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Promised FFT:

No load:
Click the image to open in full size.

8A load 1 ohm way before clipping level
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