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Subject: Re: Pulse Width Modulation (PWM) for Audio

Date: 02/20/01 at 12:47 PM
Posted by: Norton
E-mail: qopet@usa.net
Message Posted:

In Reply to: Re: Pulse Width Modulation (PWM) for Audio posted by Jeffrey Furlong on 09/06/00 at 8:30 AM:

PWM for audio application

I have developed this circuit, with 200 kHz frequency switching, in discrete components. I know a little about this. It may help you.

This called class D amplifier, offers us with hi eficiency, because of its switching mode. In linear mode, the highest efficiency could be reached at 78%, but in class D amplifier, it can be 95% or more.

This efficiency obtained from usage of power switching devices, typically FET (I use mosfet), that operate only in two modes : ON or off. This is why, we have only ignorable losses, when this amplifier is drawing a "current" output. This losses come from Rds ON of the FET, and the filter output. Filter is used to re-obtain an audio analog information from PWM output of the amplifier.

So, if u want to build a low power (???) or a low voltage amplifier, you do not have make it with this class D amplifier. If we want to convert a sinusoidal voltage from a square voltage as the output of class D amplifier, we have to prepare a dc supply about twice of the peak sinusoidal wave we hope.

Thid is my comment about this pwm for audio, or class D amplifier. It will be very helpfull for me, if someone can give me suggestion about how to find more references about this class D amplifier. I has find so many informations, from www.TI.com, about this. Any others?

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