Help me Build a Class D

[alijoorabchi]

Hi there
I am a senior student majoring in Electrical engineering at CSUN.

My senior design project is to build a class D amp with the following specifications:

Input impedance 50k
50w into a 8 ohm load.
Frequency response 100k

I have been reading a lot about it and the more I read the more I get confused.

I have found a lot of good information in this site and I have a lot of questions to ask from their designers but I am not able to email members before I post some threads. That is why I decided to post this and meanwhile ask for some help from you guys.

It would be much appreciated it if someone could provide me with some schematic and help me along the way.

Thank you

ALI

[BWRX]

What type of class d did you have in mind?

I would imagine you're looking to build an audio amplifier? You didn't actually say so but stated a desired frequency response of 100kHz which is more than needed for the audible frequency range.

It sounds like you're new to class d but read about it and got the itch to investigate further. You might want to do some searches (the web and this forum) and read more about class d in general.

[FastEddy]

BWRX: " ... I would imagine you're looking to build an audio amplifier? You didn't actually say so but stated a desired frequency response of 100kHz which is more than needed for the audible frequency range. ..."

Not necessarily just for the human audio/music range ... 2.2 Hz. thru 8+ Hz = human sexual responses ... harmonics of 18k Hz thru 23+kHz = human blood virus stimulation. Animal noises can range as high as 40kHz (bird songs). Gas turbine engines have interesting sonic information beyond 80kHz = better engine design ... so a budding engineer at CSUN may be interested in a whole ball of wax from a few tenths of a Hz (earthquakes) to 260+kHz upper limits of modern peizo-electric microphone response (so far).

Class D may be of value here if the chopper freq. is set very much larger than the upper limit of the response requirement (Is a 10 to 1 ratio good enough = 600kHz clock for a low distortion response to 60kHz audio ?).

Personally I would like to record the Hooded Monk Finch's love songs, then digitally convert and frequency divide down into the human range ... just to hear what those crazy birds are so happy about way out there past 30kHz.

[alijoorabchi]

Originally posted by BWRX
What type of class d did you have in mind?

I would imagine you're looking to build an audio amplifier? You didn't actually say so but stated a desired frequency response of 100kHz which is more than needed for the audible frequency range.

It sounds like you're new to class d but read about it and got the itch to investigate further. You might want to do some searches (the web and this forum) and read more about class d in general.

You are right i meant an audio amplifier.

I have been doing researching for a while now. i have also found some schematics from this forum and i am trying to undrestand it.

my biggest question though is how to do the pulse wiidth modulation.

any comments on that would be appriciated???

[Tomtefar]

in case you haven't found it already, this site gives some good basic information
http://sound.westhost.com/articles/pwm.htm

[alijoorabchi]

Could someone tell me how to build the pulse width modulator of D amp ,with discrete parts only?.
should i use self oscilating or one that compares the audio signal with a triangular wave???
how can i create the triangular waveshape with high frequency in my circuit to compare with the audio signal.
could someone please provide me with a schematic??

[alijoorabchi]

Originally posted by Tomtefar
in case you haven't found it already, this site gives some good basic information
http://sound.westhost.com/articles/pwm.htm

thanks