Class D university project help

[danlewy]

Hi,

I have been researching and reading on this forum for some time now, a very useful resource!

I have been given a project at university to design a class D amplifier. I am pretty new to analogue design, let alone class D and audio, so I have kept my amplifier very basic. I thought it best to use a topology that is easy to design in 'stages', so although UCD etc seem the best way to go, I decided on a feedbackless design.

The specification I have to meet isn't concerned with the audio quality, it is more about understanding design choices I have made etc.

So currently I have a triangle wave oscillator using LM319 and TLE2072, feeding into the other half of the LM219 to give a PWM signal.

Then I am using the IRS20957S chip to handle level shifting and gate driving, and am using two IRFB4212 MOSFETS. The driver caused me some trouble but I finally have it working!

I would appreciate some help with designing some circuitry for the audio input signal to the comparator. I don't know what this is called or where to start looking for information. Currently I am using a signal generator as an input but would like to be able to connect it to a source such as an MP3 or CD player.

Thanks for the great community and resources available here!

 

[nigelwright7557]

A feedbackless design will suffer from hum from the power supply on low audio levels.

You don't need anything special on the audio side just an op amp will do feeding the comparator.

 

[danlewy]

I am running short of time to complete the project. I know that it will probably sound awful without feedback, but the sound quality isn't really a specification, as long as the thing works!

So how would I configure the op amp? Sorry my knowledge here is minimal.