convert PWM to analog waveforms for audio

[pistole89]

Hi

thanks for your link. It is very useful.

If the PWM could be converted with these cascade low pass filter.
What is the function of the C3, R3, and R4 ?
These RC are high pass filter, right ?

Thanks2 a lot.

Best Regards,

 

[FvM]

A high pass filter is at least required, if the input signal has a DC offset. This is obviously the case, with 5 V PWM output, it has 2.5V offset. In addition, the high pass can be wanted to filter low frequency components, that can't be reproduced by a small speaker.

 

[alexan_e]

What is the function of the C3, R3, and R4 ?
These RC are high pass filter, right ?

You have to specify the schematic you are referring to.

Alex

 

[pistole89]

Hi

The circuit works well with the high pass filter.

However, if I do not use them, it did not work.
I tested with 8 ohm small speaker.

The square wave also consists of sinus wave with variety of frequency.
The cut frequency will only allow some specific frequency (fc = 1.5kHz) flowing.
Is it true, that if my PWM frequency is 44100Hz, the analog waveform sin would also become in 44100Hz ? (which is the construction of sinusoid wave which is allowed by filter to flow)
They only change the attenuation ?

Thanks2 very much for your explanation.

Best regards

---------- Post added at 17:17 ---------- Previous post was at 17:15 ----------

Hi Alex,

This is the schematic

Thanks