Class D Audio Amplifier

410

05:23:20

I decided to try active low-pass filtering on this circuit. The first amp operates as a comparator to synthesize the pwm signal. The LM393 would be a good choice. The other one is a low pass filter built around a power amp IC such as a LM3886. I chose a triangle for my input signal to introduce harmonics. In earlier versions of this cct I thought it made the most sense to use a linear sawtooth carrier, vut for reasons completely beyond me, it always resulted in a slanted looking output wave. For some reason, using the triangular exponential waveform seems to correct the problem. As-is this cct still has a lot of problems. It can only "reproduce" waveforms around 1 kHz. As always, any constructive input is sought and appreciated.
-j

published 9 years ago

hurz

9 years ago

You say class D but its D till the integrator opamp lowpass filter. Then how does the output of an opamp looks like. Its out is probably more a class AB or B. So the advantage of a class D amp is gone at that point and efficiency is like a normal analogue class.

hurz

9 years ago

And check the filter - make use of the bode plot feature. You will see.... http://everycircuit.com/circuit/5743618321547264

jpoulin0901

9 years ago

The main problem im grappling with is how to design an efficient passive low pass filter without having to use massive inductors I've seen a lot of class d amps come through the community, but very few perform realistically.

jpoulin0901

9 years ago

I can't open links like that on my phone for some reason.. All my component values were trial and error. Is it ever logical to use an active filter at the o/p of a class d?

hurz

9 years ago

Search for the last long number in my links and buy a new mobile ;-)

Rodrigo_bugado

9 years ago

não faço ideia do que você escreveu ,mais deve ser uma coisa legal

hurz

9 years ago

Rodrigo, start at examples you may understand better

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