Class D audio amplifier

[wilsonmasango]

I am required to amplify a PWM audio signal and then filter it to get the audio output. Please help me with the type of MOSFETS to use and the type of MOSFET driver to use.

 

[audioguru]

Why not just use a class-D audio amplifier IC?

 

[Russlk]

Has anyone listened to a class D audio? I have not but I once built a PWM sonar amp, the intermod products were only 6 dB down and I could not use it. I should think it would sound bad, but maybe the ear is not that discerning?

 

[audioguru]

Hi Russ,
I haven't heard TI's 240W class-D amp but since its PWM oscillator operates at 384KHz and its harmonic distortion is between only 0.1% and 0.3% at any output power up to max, I don't think it will produce audible IM distortion. :lol:

 

[Nigel Goodwin]

Has anyone listened to a class D audio? I have not but I once built a PWM sonar amp, the intermod products were only 6 dB down and I could not use it. I should think it would sound bad, but maybe the ear is not that discerning?

Class-D amplifiers are as good as any other, but like anything else it has to be designed to be so - your sonar amp had no requirement for quality, so could be simplified to make it easier to build.

My 400W+400W Behringer PA sounds great, you can't tell any difference from an AB amp - until you pick it up :lol:

There are also many very highly regarded top HiFi amps that use Class-D.

 

[Blatman Bond]

"Selection Guide"

here an example from tripath:
**broken link removed**
or download an16 (appnotes) for mosfet selection guide.

yes, the filter.
I recomended that you read any "buck converter" articles. It will help you to understand its function easily.

 

[mneary]

The original poster has been away for a year and a half.

 

[Hero999]

So what?

It's still useful information.

I can understand it being annoying when someone bumps an old thread without adding any useful information but this isn't the case here.

 

[Blatman Bond]

Sorry.. I'm new member.
Thanks, that's useful for me.

 

[Hero999]

Welcome to the forum and thanks for the information.

 

[Speakerguy]

My understanding is that quality class D audio amps are very difficult to design. I have never seen a DIY version that didn't basically use a pre-built chip or module that did most of the work for them. High switching frequencies are quite hard to deal with, hundreds of kHz being common.

Anyway, for switching apps, I would definitely look at a vertical MOSFET (hexfet, etc) but at high frequency maybe a BJT would be better?

It's easy enough to get the PWM signal from the audio input and a triangle wave generator, but from there it gets HARD. There's a reason quality class D has only come around in the last 5-10 years.

 

[Blatman Bond]

The designer is always used mosfet as their switching device. The reasons are simple. Easy to drive, fast, and linearity isn't important.
It's hard enough to handle the output of class-D design, that's why the designers never says that their class-D are better than class-AB.
But I believe, that digital amplifier is going better and better till now.

Thanks for welcoming me... I like this forum.