Class D audio amplifer

[kiran_shrestha]

I've designed a class d audio amplifer circuit using SG3245 and i am feeding the audio signal from computer. I have shifted the input singal all to positive side using opamp summing network . And after demodulating or filtering out the signal at output ,I get the same amplifed shifted version of the input. How can i remove the DC part that I have used to shift the signal.

[Deepak]

Not a ton of information here - like what your desired bandwidth is.

Have you tried putting a filter on the output? Something as simple as a series capacitor in your signal line and a resistor to common would remove the DC part.

[kiran_shrestha]

I have thought of doing .. so but i think it will decrease the output power of the system when filtering out at the end. So now i am thinking to use trilevel pwm . But i dont know how to achive it .

[nickm]

The cheap class d chips that are designed to work off single ended rails will either use the blocking cap or do a full bridge.  The blocking cap will be big, like 1000uF if you want response down to about 20Hz.  This is why most cheap amps use a full bridge since it just requires a little more silicon which is easier to fit in an ic than a huge cap.   The blocking cap will not reduce the available output power (unless its a really bad cap).