Class D Amp

211

03:43:36

Class D amp

published 10 years ago

thebugger

10 years ago

Ideally yes, although I'd suggest you make a sawtooth generator for the sampling wave, at a much higher frequency than the audio wave. The higher you can go the better.

thebugger

10 years ago

And the filter is somewhat wrong. The inductor should be 32uH and the capacitor 2uF for a 4ohm load and a 20Khz corner frequency response.

thebugger

10 years ago

I'd suggest to make the corner frequency somewhat lower, though. For instance my hearing has always had quite a large spectrum, and still i can only hear clearly up to 15 maybe 16Khz. 20Khz is a little of an overstretch. For 16Khz the inductor should be 40uH and the cap should be 2.5uF.

blob

10 years ago

@thebugger, yes but this is just a "demonstrative" circuit to understand how you can make a PWM from an AOP and how filters works

blob

10 years ago

But you're right ;)

thebugger

10 years ago

Yes, i get it's exemplary. I'm just making suggestions on how to improve it and make it more accurate.

blob

10 years ago

I follow your instructions ;) but, how can you find the values for the coil and the cap?

thebugger

10 years ago

There are formulas for that. There are also some apps that may calculate it for you. If you're using an android try electrodroid. It's quite handy. Anyway your modulation signal and the sampling signal are too close in frequency to each other, and the output filter can't separate them. As i said try using a much higher sampling frequency. Just design a sawtooth generator with a frequency of at least 100Khz (the higher the better), so that the low pass filter can attenuate the high frequency frequency more effectively.

blob

10 years ago

I'm already using this app! I did what you said for the component values (it's better) and for the frequency (again, it's better) but, when you mean "sawtooth" you mean 50% of rise and 0% of fall? If it's what you mean, the output don't go under 0V..

thebugger

10 years ago

I mean 99% rise 1% fall (if possible)

blob

10 years ago

Thank you :)

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