Class-D audio amplifier

Thread Starter

T.B.

Joined Jun 19, 2020
9
Hello,
I want to design a class-d amplifier using a LTC4449 n-mos gate driver on LTSpice. But there is a problem in output signal. It is not a perfect sinusoid. I realized that ,according to data sheet, the gate drivers output Bg is not at desired interval and also there is a cross conduction current issue. I tried using a Mosfet that has small input conductance but it didn't work.
If someone could give an advice, I will appreciate for


class-d-amp-circuit.PNGclass-d-amp-circuit-ts-pin.PNGclass-d-amp-circuit-bg-pin.PNG
class-d-amp-circuit-out.PNG
 

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DickCappels

Joined Aug 21, 2008
6,469
It is clipping. I reduce the amplitude of the sine wave to 4.5 volts and the output waveform looks fine.

In real life this would probably work better if you used a balanced (both a positive and a negative) power supply or capacitively coupled the output to the load so you don't waste a lot of power because of the DC offset in output waveform heating up the load resistance.

1594978041817.png
 

Thread Starter

T.B.

Joined Jun 19, 2020
9
It is clipping. I reduce the amplitude of the sine wave to 4.5 volts and the output waveform looks fine.

In real life this would probably work better if you used a balanced (both a positive and a negative) power supply or capacitively coupled the output to the load so you don't waste a lot of power because of the DC offset in output waveform heating up the load resistance.

View attachment 212341
Thanks for your reply. I didn't consider signal's amplitude. Is there any specific reason about this clipping ?
 

DickCappels

Joined Aug 21, 2008
6,469
The control circuit tries to make the output signal that goes beyond the the +20V power supply and below ground, and that's a problem because there is no voltage available to make the output go beyond those limits.

AC coupling the output signal would greatly increase the efficiency of the output stage.
 
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