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Class D Switching Power Amplifiers and Power D/A conversion

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Old 2nd March 2004, 03:36 AM   #11
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Most linear AB amps won't like working continuously in saturated mode very much - they may even overheat and blow up, depending on the outout drivers that are used. Most linear amps take their own sweet time coming out of clipping because of storage time effects in the driver (and output, if bipolar) transistors. You really want to build an amp optimized for switching operation.
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Old 2nd March 2004, 08:05 AM   #12
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Hi lumanauw,
why you want to force class AB (why need bias) for working as class D? ( a cow could be flying?) For any of class D experimentation simplest solution is a power comparator (lm319+ir2110 etc). If you'll be have such power comparator, then one week be enough for checking several basic class D circuits. But anyway UcD is most cost effective approach, IMHO. Sound & specs just fine.
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Old 2nd March 2004, 11:09 AM   #13
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No, I wont push bipolar class AB to get this self oscilating class D. The amp will be more like Nch mosfet amp (Class D likes mosfet). This will be the perfect one, just to add big LC filter at the output and take the feedback after LC
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Old 2nd March 2004, 11:19 AM   #14
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BTW, that is not my design. I found it here in DIYAUDIO.
Anyone can explain why we need R2, Q1, Q2 in that configuration? Wouldn't it formed a differential? Why the author do not connect emitors of Q1 and Q2 directly to upper rail? Why he forms a differential? What is the merit of this configuration in this particular cct?
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Old 2nd March 2004, 04:14 PM   #15
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One reason for R2 is to prevent those transistors from going into saturation which would make their response very nonlinear, and cause lots of distortion. It also would help to smooth the crossover between mosfets. But when I experimented with that circuit years ago, it was quite distorted. Also, that type of mosfet drive definitely is way too slow for class D.
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