Here is the latest iteration of my Class D Amplifier. It is a low power amplifier compared to many since it is rated at 18W RMS per channel. I use it with a 12V, 3A power supply. The design is similar to a chip amplifier that uses an integrating op-amp in the control loop. It is discrete because the TFA9815T chip amp that I was using went End Of Life. It is self oscillating at about 500Khz on one channel and 450Khz on the other. The distortion simulates to be 0.0037% THD at 1Khz and 5W. Much of the challenge of designing a switching amplifier is in the creating of a layout that does not buzz at some power level because of feedback from one channel to the other. With years of experience and after a few tries, I was able to make a clean layout with good channel separation and no buzzing. It is also very quiet. I hear no white noise from the speakers. Here is the schematic and the layout if anyone wants to see them. I am using a MC33274A high slew rate op-amp on the board instead of the TL3474 that is shown on the schematic. I edited the Spice model of the op-amp and the LM339 comparator to match my bench results. I use my amp with Ascend Acoustics CBM 370 SE speakers which are low distortion and efficient at 89 db sensitivity and I have no complaints. It gets louder than I can stand and the clarity is better than I can hear.
Attachments
I will have to generate them. My latest schematic is correct but I don't have the latest gerbers for the design. I was modifying older boards to prove the new schematic. I will need a little time to re-learn the dip-trace software.
Here are the Gerbers. Let me know how it works if you build it. It has no current limit protection so check your connections carefully before you apply the power.